GM 3400 / 3100 3.1 3.4 Engine Misfire Cause & Causes Miss Missing P0303

Here is a video for fellow GM 3400 & 3100 liter engine owners. Have a misfire? This video explains the causes for what could be causing the problem. Mine showed up as a P0303 cylinder 3 misfire. Couldn't figure it out, but finally did. The spark plug and wire were replaced along with a new coil. Could hear the injector firing with a stethoscope but still had the miss. Found out after tearing into the intake that the lower intake was cracked.
If your car is missing out, first try the following. Check for spark and check the spark plug, wire and coil. A test you can do if it randomly misses is in the dark, spray a mist of water around the plug wires. If you see blue arcing, you've found the problem. But be careful not to zap yourself, IT HURTS!
If the spark is good the listen at the injector. Is it firing and clicking? If not, you've found the problem.
If both those seem good, then check for compression. Do this with a compression tester available at any Autozone with the loan a tool program for @$40.
If all 3 of those check out then it's a possible vacuum leak. May be time to do an intake manifold gasket repair as they are known to go out. But, if you do have to do an intake manifold gasket fix, go ahead and replace the head gaskets too. You'll be glad you did. Not fun taking it all back apart again. Check out my youtube channel for these videos both on doing the lower intake manifold gasket and the head gasket.
Got questions about this engine? Leave a comment in the section below and I'll try to help!
VT247

[@johnathanconor4698]

Thanks all you utubers that help us out.May God Bless you all.

[@davidjames666]

for others seeing this video, consider checking your knock sensor, the wiring, and the connectors. it is plugged into the ignition pack on the driver side (a two wire connector)

[@toyotatech2jz814]

I actually just did head gasket job, had the heads machined, all new gaskets And they were fel pro. I have done all these test as well and still have the p0304 code. I have been dealing with this for a few months and still couldn't find the problem ND why is misfiring.and I can just barley feel it but you hear it out the exhaust . I hope this will be it. Awesome video man

[@stevensapyak7971]

A classic case of: a little bit more torque being too much! Thanks for the follow up. This will help people.

[@cguyrr]

I threw a code for a cylinder 2 misfire after replacing my lower intake manifold gasket on my 3100, so I'm pretty sure I'm having the same problem. Thanks for the upload kind sir

[@camshaftshaft2711]

Great upload I'm going through this exact problem gm 3.1 1992 #3 cyl miss code replaced injectors upper intake gasket plugs wires got great spark great compression replaced iac valve and egr and pcv and still rough idle but never stalls and loads of power when giving gas ! So now the mechanic is replacing the lower gasket and I told him to inspect for cracks! Hopefully no cracks but I'm sure I will know in a day lol! Thanks again for uploading:)

[@henrykrieger5907]

I would have never thought of this! I have a strong suspicion that this is my issue as well. I have eliminated coil, plugs, & wires. I have not done compression yet but this gives me hope. Thank you.

[@thelagmeister]

Are your valves tapping ? I had lifters lose pressure and caused a misfire. I hope you get it .

[@garystauffer2368]

Thanks , I've changed all the things you mentioned and some more than once. Your video gives me new hope!

[@jerrykemp6035]

very helpful, tearing mine back down, just replaced manifold gasket and put all back together, fired up and noticed miss and louder tap noise from motor, service engine light came on , ran a obll scan and got code P0304. tested all the wires and coils and in the process of tearing back down to check fuel injector #4 , had to remove fuel rail to do. My worst fear is the valves were not tightened correctly, causing maybe to much fuel to enter or not escape

[@timothylangdo6871]

Thank you very much I rebuilt my 3.1 3 years ago and had this cylinder 3 misfire ever since I watched this video and thought um..maybe.. well after tearing down the engine once more I found the same problem as you had cracked lower intake ..I have been trying to figure it out now for 3 years and finally it runs like new thank u for ur post it was great to see and learn something new

[@brotherb30]

Thanks for sharing this man! I'm certain that this video will help many frustrated viewers in the future. I had a leaky intake gasket so I tore it all down, replaced all gaskets (minus the head gasket), and put it all back together. It's a side project for my daughter's car, so I haven't been in a huge hurry. But it took me about 6 days, off and on, to get it done. Working on it when I had time. After reassembly, I have a misfire somewhere. I have plugs and wires to change out. I REALLY hope that I didn't Crack something. I didn't have a working torque wrench, so I had to eyeball it. I'll update with my findings.

[@thelagmeister]

Don't feel bad I had the same problem with a torque wrench. I was lazy and did mine in a week and also had a misfire when I put it back together. I took everything apart and put it back together again now the misfire is gone and the check engine light . My lifters lost pressure from sitting. the second time i dismantled it I worked the lifters with the push rod rocker assembly and before i fired it up i pulled the fuel pump fuse and cranked and cranked and cranked to build pressure. I pop it back in after i few minutes of running the valve tap was gone and no check anything lights. I hate my 3.4

[@fernesal]

You've got a lot of patience sir. At that point of the crack I would feel like slipping a granade inside and run away.

[@aprilwycherley]

Just got my car back from the shop and it was misfiring on the 3rd cylinder, and not running anywhere near as smoothly as it was before it went to the shop and is using WAY more gas. They replaced the water pump, the thermostat and the intake manifold gasket. When I complained to the mechanic that something was wrong, he said that the spark plugs needed to be replaced. I got the parts to do that, but because it was raining all day, I didn't get it done today, so will be planning on that tomorrow or Friday when I have time. This gives me a bit of a jumping off point for what to look for if the spark plus and wires doesn't work. Thanks so much!!

[@stevensapyak7971]

11.24.13. I'm doing a L.I.M. Gasket installation on a 99 Chevy Lumina, 3.1L. I'm using the Fel-Pro Perma Dry gaskets,& I noticed that the metal indexing tab is a tight fit,in the hole in the head! If it pops out and you do not notice it, when you go to torque down the L.I.M. You will crack the upper middle intake port on the L.I.M. You must make sure the metal indexing tab fits in that hole in the head! Thanks,Vacationtime247 for the follow up, this gives insight to the cause.

[@Vacationtime247]

Almost drove me crazy trying to figure out what was causing my misfire! After tearing everything back apart and noticing this, that was certainly the cause. This mistake cost me @$150 for a new intake and misc. But, lessons cost money. Good ones cost lots! VT247

[@budman1181]

wow man good eye one hell of a diagnosis glad you found it I know how it feels don't know if I have the same problem but I will be looking thanks man

[@davidsaylor7015]

You rock man! Great video and your commentary is hilarious! Keep posting!!

[@marioking983]

Thanks bruh finally a video with true details lol...I have a 2003 chevy malibu with a 3.1 engine and a cylinder 4 misfire I checked everything and I replaced my head gasket and that was the problem lol

[@dlnleloljl]

I appreciate this,thank you.and no f bombs like most other videos,excellent info.

[@sch7180]

yep,im about to do one on a 3100 engine,with the same gaskets. thanks for the info.

[@jamesmuckelrath8413]

Porsche Porsche 2005 Cheyenne

[@TERMINATORT8OO119]

Whenever I'm doing jobs like that I never trust tightening down always use a torque wrench and look at specific specs

[@RyanGralinski]

no shit who the fuck says 'i dont torque them properly cuz i want them tight' lolllll too funny

[@barryallenflash1]

My wife's van has the same issue....P0304. I couldn't figure it out...had it in 3 shops. 1st replaced the camshaft position sensor, 2nd replaced the coil pack, then fuel pump, 3rd did a diagnostic AND smoke test said it was the intake. WOW!! NO MORE SHOPS!! We are going broke. I ordered the gasket set and manifold bolts, just waiting for them to get here, then it "play time". Found a couple vids showing how to take apart the manifold and EVERYTHING that goes with it. Hoping that's it. It has about 150,000 + miles, so it's prob due anyway. Thanks for sharing this...it confirmed what the LAST shop said. I'll let you know how it goes!

[@Vacationtime247]

The intakes can crack and cause a bad miss. I'm glad I fixed this before going on a trip. It would never had made it. VT247

[@barryallenflash1]

Vacationtime247 Yes, that what I'm figuring out. I did the same as you. I replaced the plugs, wires and checked the coil pack (again) and they are all good, but STILL getting the stupid code...so, it's off with the intake!!

[@Vacationtime247]

As long as your in there doing that, it might me a good idea to replace the head gaskets. They do go bad and could cause the same code. VT247

[@barryallenflash1]

Vacationtime247 Ahhh...good idea!

[@alleneckes]

Very informative. It gives me a different perspective. Thanks

[@Vacationtime247]

Thanks! Hope this helps some people. VT247

[@stevensapyak7971]

In the Fel-Pro Tec sheet for the L.I.M. Gasket, there are two cautions that may have resulted in the cracked castings. The first one being: Vin J & Vin E engines have the locating pins offset over the port. Vin M engines have locating pin centered over the port. Also you must make sure that the original gaskets plastic locating pin is not broken off in the locating hole in the head!!!

[@eriklindblom8611]

well I just did intake gaskets. was leaking coolant. plugs,wires,coil also. NOW MISFIRING. Used felpro gasket sure hope I don't have same problem you did.

[@jim9031]

Thanks man you just saved me money I didn't have..

[@BimmerLife843]

this helped alot great video

[@silentdeath9237]

I just got done working on a GM 3400, had no compression on cyl 1 put air to the cylinder to find leaks it had none pulled the valve cover and cyl 1 intake pushrod was sticking through the rocker arm replaced the rocker arm and everything is now good hitting on all 6 and cyl 1 also has compression. If the intake doesn't open it can suck oil by the piston rings and push it out the exhaust.

[@bigfootbillunknown9511]

Thanks. Your video was quite helpful for shade tree mechanics. Now do one on getting to those pesky rear spark plugs. Coz quite frankly many shade trees, ain't limber or spry enough; to jump up on the engine block to work. 🐒

[@Vacationtime247]

Found it easier to just lift the vehicle and put it on jack stands in the front. Then reach up from behind the firewall while on the ground. VT247

[@billygreen711]

I watched your video when I was trying to determine why my 2001 malibu with the 3100 had a misfire. I was baffled when you said that it was a felpro gasket and I had just replaced the intake manifold gasket with that same one. I also knew that when i torqued down my intake I had heard a cracking sound when i torqued down the bolts. But as a skeptic I first ran all the tests: Compression, Ignition, EGR, Vacume. But all the results led back to the intake manifold being cracked. I disected the engine once again to discover that yes the lower manifold was cracked over the port for cylinders 3 & 4. I found a good lower intake manifold at the junk yard, $25. I purchased a smaller torque wrench and a set of flare nut crows feet from harbor freight tools. I followed the torque specifications putting the car back together. The car starts and runs, i'd say it has a little fluctuation in speed at idle but when i take it down the road for a test drive it is like the car still has a cracked intake.

[@Vacationtime247]

Both the upper and lower intake manifold was cracked on mine in the middle. Got both for @$50 at a local junkyard. Have you tried spraying water or carb cleaner over different areas on the motor / intake and monitored for idle change? Mine however was cracked on the inside / oil valley. Hopefully you changed the head gasket too, they tend to go bad. VT247

[@billygreen711]

Vacationtime247

[@billygreen711]

billygreen711 This is what i hate about these forums there is a whole history to my car that you have no idea about. So I guess i should have started from the beginning. My father in law bought this piece of shit car from his neighbor for my wife in 2008. Low miles,tan. When I first changed the oil in 2008 I noticed that there was oil on top of the coolant cap and it was a little low. So I always had to add maybe a quart of coolant a month. We let our 16 year old son drive the car and he really put some miles on the car driving the neighborhood around. He ran the car low on coolant and I do not know if he shut the car off or he shut it off. But I had put some coolant in only for it to leak into the engine. It had coolant and oil mixxed bad That was August 2013. I replaced the head gasket, fel-pro, and lower intake manifold gasket set, autozone brand, with it lasting about 4 months and I was loosing coolant again. Once again my son was driving it and ran low on coolant. I asked him not to drive it because I needed to fix the the coolant leak. One day later he drives the car without coolant. He comes back home and begins to fill the car with water. I realized that he had filled the car with more than a few gallons of water and asked him to leave his car here so i can figure out what is going on. When I looked at his car I realized that water was now dripping from the exhaust while the car is running. I tore the engine apart checking the gaskets. I did not see a cracked block or head. I replaced the head gasket with the Autozone head gasket set that included the felpro lower intake manifold gasket. This is what led me to start of the post.

[@Vacationtime247]

1. Tighten the vertical lower intake manifold bolts (1) to 7N·m (62 lb in). 2. Tighten the diagonal lower intake manifold bolts (2) to 7N·m(62 lb in). 3. Tighten the vertical lower intake manifold bolts (1) to 13N·m(115 lb in). 4. Tighten the diagonal lower intake manifold bolts (2) to 25N·m(18 lb ft). But I just tightened them up by hand being careful not to over torque them again. VT247

[@angelandazola1568]

You hope this helped somebody? Buddy thank you

[@andrews8883]

Couple ques: My push rods got tipped over and mixed up. U guessed it i put the exhaust in the intake, bent it pretty good my ran it w/o driving it. Do u think I bent a valve??

[@HandyTim]

I had the same thing happen with a dodge grand caravan 3.8 felpro gasket. everything was torqued to spec but because the gasket was faulty it cause the intake to crack

[@92sonoma]

I been working or cars and even building engines for over 20 years. here recently my brother and i have been trying to figure out a missfire on a monte carlo with the 3100 engine. keeps showing a cylinder#1 missfire. have tried a coil, control mod, spark plug wire, spark plug and fuel injector and its still there. they were all perfect working used parts also. car has around 130,000. im suspecting a bad intake gasket. whats your thoughts, thanks for the vid

[@Vacationtime247]

The misfire was most notable at idle. But I'm sure it was doing it all the time, just less noticeable while driving. Could be the gaskets too, the head and intake gaskets are known to go bad. Especially if stock. Sorry for the late response. VT247

[@alexdergacheff8135]

I have a 2005 Buick century in great shape, only 69,000 miles. At idle, it seems to be running a bit rough. I can feel small vibrations through the seat and the steering wheel. This is accompanied by a knocking noise that can be heard occasionally. I know the 3.1's knock when cold, but this is after it warms up. You cant really hear the knock from outside the car, but sitting inside with all the windows up I can hear it, it's a low pitch deep knocking. Not severe, but noticable. I just want my old grandma car to be happy and smooth! Any ideas? Thank you very much!

[@kameron454ci]

i have had to helicoil four rocker bolts on my 3400 i did all of them with the head on and without pulling the intake. it a very common problem and no big deal to fix

[@ethanwebb9338]

A friend and I recently replaced a cracked lower intake manifold (around coolant temp sensor), gaskets, coolant temp sensor, thermostat, spark plugs and spark plugs wires. I have got a P0300 code twice. I feel a rough idle and then some hesitation when accelerating slowing. This never happened before these replacements. Don't really want to tear it all apart again. What would you suggest?

[@vincentrawls9144]

I'm heaving a misfire on a 1999 Buick central I changed all the spark plug and the coil but still got the misfire

[@oscararreola20]

I have the same problem with a 99 Cadillac Eldorado and I changed everything and still have a misfire on to spark plug wires. I changed the coil also what could it be intake manifold leak

[@AshAndCamilleMiller]

I did the LIM gasket on mine, didn’t mix up pushrods, as far as I can remember the felpro fit just fine. I did hand torque everything down just by feel, the gasket appears to be functioning fine, I completely cleaned everything out even including a toothbrush to the overflow tank, no mix I can tell at all, no bubbling in the radiator when on. The engine did overheat a bit but not that long, it never pegged out just got real close to red. I don’t see any obvious vacuum leaks or hear anything, this is the second time I did this stupid gasket, ended up cracking the LIM due to removing a bad temp sensor that someone cross threaded. Got a 2 LIMs one from eBay but then found one in a nearby junk yard. Well needless to say the engine idles rough sometimes, high speed seems good, sometime it idles better until warm, no rhyme or reason. I just can’t see myself doing this stupid job again until cross contamination occurs. Not sure if I have your issue or not, the car has run pretty decent for 20k miles. All ignition parts are new, I think I’ll just live with it, maybe head gasket maybe LIM gasket didn’t seat properly or has an issue like yours. Who knows, I refuse to do it again, when something starts to fail then I will just pay someone to do heads and LIM for me. I’ll catch it way before any bottom engine trouble. That job is the biggest pain in the @#$. I just won’t get rid of the car, it’s a fun car 3100 century station wagon with immaculate paint , interior, and all rubber window seals etc. it was kept in a garage it’s whole life. I changed LIM gasket on a 307 Buick with quadrajet in like 30 minutes this one takes hours and the risk of damaging other components like rockers etc. small miss whatever it runs decent enough to drive and not act a fool. I sure wish there was a simple test for this, I’ve done a lot of stuff troubleshooting that didn’t turn out to be bad, I’ll be damned if I take that all apart over a little idle miss that gives no codes. Autozone sells the 3100 and so do other places might just drop a new motor in it, but ONLY if I can find one with the LIM on it. Oh well project for another year or whenever one of those gaskets fails....

[@Vacationtime247]

Might try a coolant pressure test to see if it holds pressure. These engines are horrible for blowing gaskets. The head gaskets only last for so long before taking a dump. Every 3400 I've ever owned has needed all the gaskets replaced. VT247

[@Vacationtime247]

Besides the intake manifold gasket, guess what else goes bad in the 3100 / 3400's. The head gaskets. They get brittle and fall apart. Could be the cylinder has to much air entering the chamber such as a lean misfire. Or coolant entering in the cylinder. Also, check for a vacuum leak by spraying water. Then listen for rpm change and a suctioning noise. VT247 VT247

[@stevooliver3877]

The last plastic gasket guide tips get broke off in the in the heads..make sure taps are clear might have not enough clearance..plus the metal tabs are to make sure you don't torque to much to compromise the gasket..just a safe guard to protect the seal...also your 4 bolts on the side of the lower intake can be stopped up with threadlock,sealer,etc...drive the bolts in the holes until it stops before you install the manifold . some bolts are not threaded all the way but make sure it goes far enough to torque the gasket instead just torquing a stopped up hole..lots of fun..good luck

[@metoowahl]

On these particular gaskets. Use a punch and tap the guides into place so that they stay in place and not get ruined during installation of manifold.

[@tecknows]

I have somewhat of some issues too. My 3.4 Impala is using oil, my water pump seems to going as I'm losing coolant, it doesn't seem to be in the oil, and I watch water fly off of the water pump pulley. She's also having fuel issues. Fuel is pooling up out of the top of the fuel filter. My transmission sometimes won't shift right, and has a terrible noise when idling (presumably from heating up due to the coolant issues). I've always taken very good care of this car. The suspension is all brand new except I have both control arms with ball joint's that need to go in. I dump money into this beast, as when it runs it runs great. But these issues all at once are causing me to some major grief at the moment. I definitely appreciate your video. If anyone has any insight, feel free to let me know!

[@Vacationtime247]

Do a coolant pressure test of the cooling system to find the leak. May need a new fuel filter. Transmission not shifting right MAY be fixed by doing a fluid and filter change or might be the PCS solenoid inside the transmission. VT247

[@tecknows]

Vacationtime247 Thank you sir. That is the concensus.

[@tecknows]

The Band's and pump are shot. Got the new one yesterday, old one will come out today and new one may even go in. Merry fing Christmas!

[@dman2902]

Hi I have a 2003 chevy impala and I put new lifters in it and added a new rocker arm because I destroyed one from driving the car with out no oil in it and I didn't know that It didn't have any so I fixed that issue but then my car is running poorly at idle now and I see gas coming from the fuel pressure regulator I wonder if that had something to do with the bad idle or is it a misfire because my exhaust sound like it's putting a little bit and also I'm trying to see why it's burning so much oil to

[@Vacationtime247]

If you've never replaced the intake manifold gasket or the head gaskets, they are highly suspect. Both go bad over time. Pretty much every 3400 I've had has needed both replaced at some time. Usually to find a bad gasket it's a process of elimination. Spark, Fuel and compression. In that order. Spark is ok, I'll assume the fuel is ok, next check your vacuum reading. Vacuum can help diagnose many problems also. Check compression and possibly a leak down test. VT247

[@Vacationtime247]

Thanks! Couldn't for the life of me figure out why it was missing out after having fixed it. Guess I got a little over zealous when I torqued down the intake bolts : / VT247

[@redneckbryon]

Good Video

[@Reloader826]

WOW ... Thank you for such Great Info Update ... Sorry it cost you Time and Money ... But Thanks and Please keep Up such Great Videos ...

[@Vacationtime247]

This one really threw me for a loop. Couldn't figure out what was going on. Wasn't until it was all taken apart and inspected closer did the problem become more obvious. Fixed it and drove it several thousand miles more. VT247

[@alishacrabtree8782]

Good luck

[@Vacationtime247]

Seems I'm not the only person that's done this either. There are a few others that have experienced this issue as well. People would post their odd misfire about this engine online but never with a follow up on how to fix the problem. So in case someone else out there has done this, now they know how to correct it! : ) VT247

[@briantsosie4315]

Do you know where the orifice tube is located in the 3.1?

[@andrews8883]

I ran it a total of 30 seconds without driving or revving. Have u done this? This is to clear up the last post

[@Vacationtime247]

With any luck, it just bent the pushrod. But without pulling the head, it's hard to determine if the valve was bent unless it's running rough on that cylinder. If it runs rough, the valve may be bent. Hopefully it isn't. VT247

[@bigblockdrf]

did it only msfire at a idle but drove fine i have a 01 montana cylinder 4 random misfire i changed plugs wires coils coil base every time i tried somthing new it ran good for couple minutes then the misfire came right back

[@maharper100]

I was afraid of this, I have the same issue with mis-fire on cylinder 5, changed wires, plugs, coil and even replaced fuel injector. Guess I'll pull the intake and replace the gasket.

[@migueldelvalle3871]

just had an issue with that too. the problem with my car was the rocker arms came off on intake and exhaust. put a hela coil in both.

[@briand2195]

Miguel Delvalle that's a first I've heard of. any ideas as to how that happened?

[@waynedoyle86]

Mine Rpm hand is jumping up and down when I accelerate and it starts hesitating and when I decelerate the Rpm hand begins to read but the car is not missing I replaced the spark wire

[@shanewood6129]

Is there a way to check for a crack without having to disassemble everything? With a scope or something? I believe this might be my problem, the previous owner had re-machined a head and changed the head gasket. So is it possible they cracked the intake manifold? I’m a little scared of digging that deep especially if I don’t have too. But I’ve been searching everywhere and this makes sense as the fuel injector has been replaced the plug and wires are good and I’m getting p0204 p0304 & p0404 I have a 06 Chevy Equinox 3.4 Thanks for this video!

[@Vacationtime247]

Might put together a DIY smoke test and push it into the intake or the brake booster hose after plugging up the front of the intake throttle body. May also be able to get an idea of this happening with a vacuum gauge. Also could try using carb cleaner and checking for vacuum leaks with the engine running and checking for changes in RPM. Just a few suggestions. VT247

[@MrCOOLassSHIT]

i was told to go by specs and you said a tight as you can are both right

[@ag88771]

What's the torque on a lower intake on 2004 Pontiac Grand am?

[@larrydolin3534]

1998 oldsomoblie silhouette 3.4 when we are at red light it starts to miss and loses rpms and I have to keep foot on brake and give it gas while sitting at light pulling out sometimes it hestie and misses and jumps

[@Vacationtime247]

larry dolin Check the vacuum lines. My Alero did the same thing. Turns out it was the vacuum tubing from the PCV and the intake.VT247

[@tomnewsom8943]

+Vacationtime247 what is the timing set where is number one forward​ A330 r31 engine V6

[@Daveyboy919]

Sometimes if the mass air flow sensor is bad it will throw that code

[@MrDrizzydrake51]

I have a 98 Malibu 3.1 that I haven't driven in 2years because of a 6 cyl misfire changed everything and still misfire and cel flashing so now I guess I'm tearing into the engine soon thanks for the in site

[@michaelbrown497]

I would call that a intake leak or vacuum leak not necessarily a misfire if all of the ignition components are working correctly. It will more or less stumble.

[@davidcooley5135]

I took mine apart and found the same thing was going on but mine was pulling in air somewhere and it was over heating

[@insurancedice]

Would a smoke test have shown this crack? It would be under the upper intake but it'd still leak out, right?

[@Vacationtime247]

Possibly. Depends how wide the crack is and if smoke could get through. VT247

[@kennethrome5125]

VT247, Question on the Lifter. The new one Napa gave me has a spring loaded top seat for the pushrod, but all the existing lifters are not spring loaded and cannot be pushed into the body of the lifter. Is this just an updated version or is this the wrong part. TIA Ken

[@Vacationtime247]

They're probably a replacement type lifter. Once the lifter is filled with oil it can be tough to compress it down. Soak the new lifter in oil to allow it to fill up with oil or submerse it in oil and depress the plunger to prefill it. VT247

[@trentonflemmons2130]

I have had this problem a few times and 4 times the lower intake gasket dowel pin was slightly oversized causing lower intake to crack. Now for the top intake they seem to be cracking once I go on the 3rd pass or second pass to tighten them to 18 foot pounds as a service manual says but if I only tighten them to 115 inch pounds I don't have any problems with the intake plenum cracking so my question is what are the torque specs I have followed the torque sequence the enters first then the atoms in a cross pattern but what should the proper torque specs be so these things will not crack because it seems to me that the aluminum intakes are porous and Contour so when you tighten them down they have they don't sit totally flat

[@Vacationtime247]

Personally clean every hole with an air chuck and clean the threads on all the bolts. One had a plastic dowel pin broke off inside the locating hole. VT247

[@jasonyates5162]

mine is doing the same but it's drips water above the thermostat

[@longmirewest9460]

I have a 2002 Buick Rendezvous 3400 by chance do you know the firing order for spark plug wiring? Do you believe the 3100 in the 3400 same have same firing order?

[@Vacationtime247]

Believe the 3100 and 3400 are the same order cylinder and coil pack configuration. The following info would be for your Rendezvous 3400 motor. Front of the car, near the radiator, from left to right are cylinders 2-4-6. Back of the engine, near the firewall, left to right is 1-3-5. Now the coil pack, as mounted on the engine from left to right is 5-2-3-6-4-1 VT247

[@kennethrome5125]

VT247 ....What procedure is there to replaced a Hydrlc Lifter ....Just pull the intake or must the head come off ...and the lifter pulled out from the top ?

[@Vacationtime247]

It's about the same as doing an intake manifold gasket repair. But check the rocker arm bolts as well, they supposedly can strip out. The lifters are roller type with a guide on each side, 2 bolts hold down the lifter guide. Check each pushrod for play at rest / no tension. Intake & Exhaust pushrods are different lengths. Also, it you get to this point, I'd recommend to go ahead and do the head gaskets. They get brittle after time, loose compression, leak antifreeze and blow. Replace gaskets from the heads up and these engines run forever! VT247

[@candicehuston1747]

On a 3.1 v6 motor does it matter if the valves are up or down when you torque the rocker arms down?

[@stevensapyak7971]

2.6.16. You need to make certain that each cylinder is at top dead center (TDC), when you loosen to remove the rocker arm bolt & remove the push rod, when the lower intake gaskets are changed! The same goes for when the rocker arm bolts are torqued down!.......Or when you go to start the engine, you'll have the dreaded loose rocker arm syndrome! (Stripped aluminum threads in the head) 😢. You can also purchase the Lisle 48300 rocker arm tool, to avoid loosening the rocker are bolts, when changing the L.I.M. Gaskets. It comes in handy if changing the head gaskets. 🎯

[@MustangSteve]

I am working on one now, 2003 chevy venture. I tuned it up with new plugs, wires, coils and crankshaft censor, and it still shows multiple misfire, sometimes #4 cylinder. I ran a test by pulling plugs 2,4, 6, all on different coils, and all had good spark, the #4 plug only was shiny like new, I could tell nothing is firing in that cylinder. Next step, check fuel injector to make sure fuel is going into it. If injector is working properly, what else would I look for.

[@Vacationtime247]

Check fuel pressure, might be a weak pump. The spark module that sits under the coils could be going bad. Try unplugging the MAF (mass air flow) sensor, see if that clears it up. Check for vacuum leaks. Don't forget the camshaft position sensor too. Just giving a few things to check for with a random misfire situation. VT247

[@joeycameron4744]

oh no....I just did the LIM job on my car...for the third time since I have done a head gasket. I remember that metal tab not wanting to fit flush into the hole....and my car is sputtering at idle and popped up a P0303 and I've replaced coil, plugs, wires, injectors, O2 sensors. And my first lower intake had that exact same type of crack on the middle runners. I don't want to tear it down again...I just got it put back together :-(

[@Vacationtime247]

Joey Cameron Not a fun job to take off and redo. Always have problems getting the hoses on and the power steering pump put back on. VT247

[@doogie9174]

tomorrow am going to tear it all apart again !going to check for cracks ect!if its not the problem could it be the injector on the fuel rail? even though it clicks like its working

[@joshrifenbark1347]

Check your fuel pressure regulator

[@timmyparkerson1800]

did a intake gasket replacement now engine has a loud lifter knock sound in it . took it apart again put it back same thing not sure if lifters are pumping up or what t2or3 lose the oil after sitting awhile need help ??

[@Vacationtime247]

Probably a stripped out rocker arm. Check there first. May sound like a lifter but could be the rocker. VT247

[@seanmiller6495]

So a intake gasket leak will cause the misfire..minebhas a cylinder 2 misiffe.anf I can't figure it out..but I do have a gasket leak right where cylinder 2 is.

[@Vacationtime247]

Yeah the extra air is not metered and throws off the air fuel ratio. It's like having a bad vacuum leak on that cylinder. VT247

[@stoplight6969]

vacationtime 247 done the whole ordeal new gaskets no coolant in oil but water coming out exhaust and running poorly do you recommend pulling the intakes and checking for cracks didn't do it before

[@stoplight6969]

Email me at [e-mail]

[@Vacationtime247]

Did you do the head gaskets too? They are known to go bad and cause this issue. VT247

[@thomasbowery8200]

I have a Oldsmobile cutlass 3.1 v6 did the timing on it and rebuild the engine but it's not wanting to start think the push rods were put back in wrong how do I find out the right order they go in

[@Vacationtime247]

Intake pushrods are slightly shorter than the exhaust. Should be easy to identify which is exhaust and intake by just looking at the ports. Make sure all the connections and wires are connected to the coil pack / ECM VT247

[@ryanwilliams3369]

Mine was a lifter issue on #5

[@mikehoward6433]

Changing front valve gasket on 04 Buick randevous any advice?

[@Vacationtime247]

Check the oil pressure sending unit. Sometimes it may appear that the leak is coming from the valve cover but it's usually the sending unit. Above the starter but below the valve cover. But if it is the valve cover on the front the biggest problem you'll have is that stupid black coolant tube going over it. It can be lifted out of the way once the bolts are removed under the throttle body. VT247

[@minivanmadness2345]

It's great u can admit your mistakes

[@douglasmoorhead3037]

We're is modular at on 1995 pontiac transport 3.1 v6

[@stevenzuel6499]

Hey where did you find the upper and Lower I have the same exact problem just can find one for s reasonable price I have a 99 Monte Carlo ls 3.2L

[@Vacationtime247]

I'd say a junkyard is your best bet. These engines come in a lot of different cars. Grand Am, Alero, minivans, etc. VT247

[@emenem6131]

I did the same thing bro....what the heck did those metal pieces have to be in there????? Just to break them.... I used a cheap set from China that lasted for 4 years...no metal inset in the gasket....I thought this time I would go big and spend the 90 bucks and not have to do the job again.! WRONG!! I torqued to just over 10 inch pounds and placed a perfect indention in both 3 and 4 exactly what you pointed out.....so mad I could have bit 16 penny nails into. And if you notice the other seals including the coolant seals have NO METAL pieces like the two intake in the middle....I’m still mad about it.

[@montetolsmatolsma2524]

My wife drives a 94 grand-am with the 3100V6, it just turned to 100,000 m and problems start. Fuel line's rotted so I replaced, and the brake line's as well because they looked just as bad. Now after installing a new alternator and battery it will barely idle after start up. There is no power at all. Fuel pump pressure is 38 on and 35 running. Plugs and wire's check out, not had chance to check injectors , when looking at wires leading to injectors I found a lot of them that the insulation was cracked and falling off. Would that be the cause or just a part of the problem?

[@Vacationtime247]

Need to find out why it's missing out so bad. What codes does it have? Is it random or cylinder specific? Pull individual spark plug wires off and see if that makes it worse or no change. Helps isolate which cylinder is missing out. Just a few things to check, check for strong spark (coil packs and coil module). Vacuum leaks, can check with carb cleaner or mists of water, noting idle change. To check fuel injectors I plug one ear and then use vacuum tubing (one end in your ear the other to the injector)to listen as the injectors cycle. VT247

[@mlez7197]

They have needle torque wrenchs on sears for $12.00 i just did mines and there fine

[@mikegeary7319]

See with my 08 equinox 3.4L I get a jerking hesitation on a incline and around 55mph on highway. I got the lean bank 1 code on a diagnostic. Ive changed the plugs and wires, coil pack was my next guess

[@Vacationtime247]

Also might be a fuel injector being that it's lean. VT247

[@ogamhunter]

I was clearing out parts to get to my upstream o2 sensor. As I was removing the coil pack, I noticed where my #1 plug wire is on the coil was very rusted. Is this caused by not firing or warm air cooling and trapping under the connector cap on my plug wire. Or could be something else and could I clean it and use Die-grease on the prone' s and inside the connector caps and hook it back or should I get a new one?

[@Vacationtime247]

+Glen Riffe It's not that much to replace it. Just get a new one. But if you're trying to save bucks, clean it up with some sandpaper and check the spark. VT247

[@ogamhunter]

+Glen Riffe The coil at #1 was cracked, bought a new one. The wires and plugs have all been changed also none crossed. Still having a backfire and stalling problem, just in gear when you want to throttle it. Idles great. Cleaned ground ends on transmission. Fuel pump works fine also. MAF changed, Throttle Body cleaned, both o2 sensors changed, opened up the catalyst converter. I do know I have a ground because my dome lights stay on. Door locks lock on their own when I exit the vehicle. Can my module ground out?

[@Vacationtime247]

Check your fuel pressure regulator, crank positioning sensor and cam position sensor. Does it throw a code yet?

[@troylively5995]

I changed the head gaskets on a 01 3100 sfi and during cranking the vacuum hose on the fuel pressure regulator keeps blowing off and I'm getting a backfire through the throttle body what could be the problem ?

[@Vacationtime247]

+Troy Lively MIght be a stuck valve or lifter. VT247

[@harrisdarryl6]

Shoulda used a torque wrench and set to factory specs. Over tightening anything is a problem. I get torque specs for every bolt i remove(clean threads well) and torque to factory specs. This ensures fasteners won't break or strip aluminum part or threads and the deck and intake surface are evenly sealed. The felpro gasket set you used is assign excellent solution to bad engineering. Instead of a plastic gasket they came up with this great solution so you can make another 100000 miles without coolant leaking in the intake runners

[@mikecole4170]

My pontiac grand am gt has a miss fire.3400. I have changed the coils,spark plugs and wires ecm and more but it still is miss firing.but my check engine light is not on.what could the problem be?

[@Vacationtime247]

Check for a vacuum leak. Pull off a spark plug wire then start the car, see if it makes a difference in how it runs. Runs worse, that's not the right cylinder, runs the same, you've found the area of the problem. Might be a fuel injector. Also possible that a gasket is bad. Hope this helps some. VT247

[@aaronwoodruff4600]

I have a po305 code and you cant give it gas and it miss fires at idle thing its my injectors it runs loke crap

[@stevooliver3877]

Another tip..rods are cheap..if you remove the rods with the lisle 48300 rod remover put in new ones in..the intake rods are $3 & exhaust are $ 5 a piece..do the exhaust rods first they can only go in the right place ..then do the intake rods ...rocker bolts or nuts are too soft to break loose or retorque..it dont take much pressure to raise the rocker with the tool..its about $20..but if you have the snooty mixture you might want to take the lifters out clean & soak them in a assembly oil while cleaning the port chamber just push down while in the solution ..oops I'm sorry I don't want make seen hard..but seen way too many broken cams & spun rod bearings if you don't get that mixture out of your oil channels..many ways to do it starting with the oil filter inlet port...fun fun fun

[@d46313]

I have a 2002 gm 3400 in my rendezvous (same gm recall different shell) I have a horrible half grinding half chatter noise comming from the rear left (looking at the motor from the front of the vehicle ) under or right next to the alternator. And it only happens between 2700 and 5000 rpm. On rpm increase its pretty quiet one rpm decent it's louder than hell. Also have a small almost inaudible chatter at idle. What could this possibly be or what could it possibly morph into (as in bigger problems wise) Sincerely, Upset gm owner.

[@Vacationtime247]

My guess is that it could be the belt tensioner or a stretched serpentine belt. Mine used to squeak until I replaced the belt. That's where I'd start. The diagram for the belt routing is located by the power steering pump. VT247

[@htatesil4192]

Will it start with the pushrods in wrong position

[@Vacationtime247]

I doubt it. It would make a lot of noise and could even strip out the rocker arm studs. VT247

[@steveallen3013]

2001 Pontiac Grand Am lower intake replaced hard to start stalls out and misfires like crap low Vacuum vacuum needle jumping all over the place fuel pressure is good map sensor code po107 po108. Missing on Cylinders two and four mainly also sex not as bad the front side let me know if you can help just did the lower intake

[@Vacationtime247]

Check for vacuum leaks. Make sure all the connections are plugged in at the coil correctly along with the MAP. There are several connections and know I've missed one when doing this job a time or two. As in this video, if the mounting tabs for the intake don't line up correctly, it can cause the aluminum intake to crack when torquing the bolts down.. This was my problem as seen in the video. Another thing is that the intake and exhaust pushrods are of different lengths. If they are not in the correct configuration, it will cause running issues. Hope this helps some. VT247

[@cameronhale2283]

i have a 2001 grand am gt 3.4 that has a random misfire in cylinder 1. the fuel was running rich and now the fuel is running fine but i still have the random misfire. Help?

[@Vacationtime247]

Check the spark plug, wires and coil. VT247

[@tarnimant1463]

how do I conduct a engine combustion test on my 01 impala? 3400 gm engine v6

[@Vacationtime247]

Can do a compression test by threading a test kit into the spark plug hole and cranking the engine over. Should have well over 100 psi and all of them should be within around 10%of each other. If it’s missing out, check the spark, fuel and of course a coolant system pressure test. These engines had known issues with bad gaskets from the factory. Nearly every one I’ve had has needed the entire gasket assembly replaced. Such as the timing cover, head and intake gaskets. If you have to do one, do them all. Having to go back later and do things over again ain’t fun. VT247

[@tarnimant1463]

@@Vacationtime247 ok thanks I just replaced the head gaskets and both lower and upper intake gaskets. I want to do the compression test to check my work. This was my 1st time attempting something like this. Trust me im no mechanic