99 Astro van 4.3 P0304, p0300 misfire fixed!

[@freddaniali]

Todd, when I lifted the body on my 05 to replace my engine, I found a bunch of damaged loom and burnt wire. I went through and repaired it all and it solved all of my ghosts and gremlins!

[@stevehowe4381]

Todd's right... check all your wires. I had a 95 Astro that the transmission started shifting funny at 70,000 miles and I knew it wasn't the trans. After searching for 7 days I found a connector that had about 9 small wires in it that went to the computer and the connector contacts were corroding, cut it out and spliced the wires and put another 300,000 miles on the van!

[@pacora07]

LOL it happened to me too. I drove pretty much with a bad 3/4 clutch packs from Florida to Minnesota, and I survived by using the towing feature button on and off. some how it resets it to normal driving conditions. when I got back i found all those wire were corroded and contacting the metal frame of the van. I cleaned them up, spliced them and never had that problem again, after, i overhauled my transmission and with all the wire fixed I have a transmission for years to come.

[@mikepeterson918]

Great job! Now that's a real mechanic that doesn't give up.

[@patheightyeight1359]

Bless you angel of the garage dark arts. I'm not a mechanic, but this is exactly what's happening to our Astro Van. Multiple trips to the repair shop, tons of parts replaced, and nothing but scratching heads and a "we don't know what's wrong, you'll have to take it somewhere else."

[@adventureswithdougie]

This is great information as my 2002 safari misfire on cylinder 3 under load. Even Gm cannot locate the issue. Thanks

[@lysias55]

What was it for you? On 2001 Astro the Harness no longer takes this route

[@richardthompson8890]

Todd, Thank you SOOO much for posting that! 98 Safari, EXACT SAME PROBLEM! I was totally about to give up and take it to a shop. Replaced coil, cap and rotor, noticed the distributor was sloppy so replaced that too, still had random HARD miss, and it was getting worse. Was about to change the injector assembly, and figured I would give KZbin 1 more shot. Watched YOUR video, grabbed the harness, and the van shut off. I cannot believe that something this simple is so damn hard to figure out, lol. YOU ARE DA MAN!

[@toddambroziak4751]

I'm glad I could help. I don't post much on you tube but I figured I would on this one cause it caused me many sleepless nights trying to figure it out! Hopefully it will help out more people!

[@rayzztera.3171]

@@toddambroziak4751 I'm having same misfire P300 code too under load, going to check it now, thanks!

[@jeffsharp6652]

Thank you so much for taking the time to share this issue with us. I have the same symptoms with my van. Time to start checking for the same problem.... Thanks again !!

[@StueartMill]

me too!!!

[@toddambroziak4751]

Yes it was! The control wire was grounding out causing the fuel injector to stick wide open and dump full fuel into the cylinder intermittently. It felt just like an ignition miss. This was definitely an odd one!

[@jrea424]

I will have to check this out, my 93 astro is a running project, I replaced everything apart from needing to test the fuel pump pressure etc. She is missing like crazy under load similar to what you describe. When I take out the spark plugs theyre all wet

[@wlentz2598]

@@jrea424 I can see the black mark from the arcing...outstanding !

[@livingyourbestlife711]

Thank you for sharing! An intermittent misfire is aggravating. You change this or that but still, misfires. Only on D, ok on N or R. I have the same problem. I will start looking for a short somewhere! Glad you found it, Todd.

[@charlypetra191]

Same history, same parts replaced...same codes, same miss.... going to check tomorrow. I was headed to the temp. sensor and 4th search for vacuum leak...eeeeeh I had checked all of the harness issues reported but the one you found. Thank you

[@JohnDoe-jj8sp]

Your the Man, my respect to you buddy....i have a 2004 astro van.n I'm in love with the vans, I had 3 mini vans...very dependable..

[@thesilkymodine]

I’m dying over here! This brings back so many memories of busted knuckles. Still love the Astro van though.

[@fouroakfarm]

This is a great video to share, thank you. Problems like these are hell to track down. Wiring on these old vans has me pretty concerned. I just yesterday fixed my unstable VSS issue when I found one wire at the sensor connector was broken but INSIDE the insulation, couldn't see it

[@danstinson7507]

Your description at the start sounds almost exactly like our experience with our 2002 Astro. I'll be checking on this in the next week. I can't believe they let the split in the plastic wiring jacket fall right where the wires can slip out! Well, yes I can...

[@electricguysvcs]

Thanks man. I've been going through the same thing with my 99 Astro for a few years off and on. I have no hair left

[@codywatson95]

Lmao, man I hear ya

[@cornelieusfields2062]

You always check your wires first spark plug wires electrical wires. You always run them down. I had somebody's vehicle that wouldn't start it all. There's out there for 3 days trying to fix it. It only took me 15 minutes to find the problem. Sometimes a wire will break inside insulation and you have to know what you're looking for. And that's what happened on this one guy's vehicle. Here I solved his problem is fixed it and then he didn't want to pay. But he was out there for 3 days. I just walked away from him and said forget it.

[@deelopez4986]

​@@cornelieusfields2062 Dirtbag

[@HB_Stuff]

I've been driving/repairing these vans for 28 years and have not heard of this issue before. Thank you for the video adding a bit more Astro knowledge to my repair arsenal.

[@Gunner_144]

Hello mate, got one and it’s start but when you go to put it into reverse it stalls and won’t start almost seems like it can’t idle itself properly any common things? @ihatemybike

[@bigsticksbananaclips4575]

@@Gunner_144I am having the same issue due to low compression in cylinder 3 which I think is caused by a burnt valve idk if that’s your case or not

[@brownlee62534]

You're the man. Mine would buck and stall going uphill with less than a half tank of gas. I'm thinking the fuel level has crap to do with it now. I'm clearing that wire today. I'll let you know how it goes.

[@lowellmayfield5736]

My silverado 1500 4.3L is the same way, usually when the fuel gets below 1/2 tank and it is damp outside, and only when the engine is under load. I have to coast in neutral or it'll die when I let off the gas, and it'll buck when accelerating. Today I ordered a new distributor, wires, plugs. I replaced the mass airflow sensor a few weeks ago but it made no difference. Anyway, in the morning I'll inspect the wiring and I hope I find a short somewhere!

[@globally123]

I also am in the midst of being in this rabbit hole,I will check on this right away. Thanks for sharing with the GM Community cheers.

[@andresmolina4315]

Thank you for this video! I have a Oldsmobile bravada 1999 4.3 liter and I'm having a similar problem.

[@edwinaviles318]

Thanks! That solve my multi misfiring . I was going nuts trying to find the cause. I swappped everything with the exception of swapping out the motor completely. Lol.

[@rafaelgamboa4321]

Good job man. my van has the problems with the cap routter. I change it now is good but I have other problems my cluster is has a electrical problem too.

[@mikewitte7379]

On my 2000 express 4.3 the distributor sensor was intermittent and replacing it fixed the problem. 35.00 after i replaced the EGR Plugs Wires Cap. Just saying its worth changing before the cost gets away from you.

[@leelemon3373]

Pit Bull Mechanic. wouldn't stop until he fixed it. Great job and Thanks for sharing. I have a high Idle. But you taught me something.

[@anthonylagrasta1148]

We're struggling with similar, anxious to get home and look for the same fault. Thank you for ht post.

[@Sjetton85]

Definitely be checking this tomorrow.. yeah when it's damp I've had rough idle..

[@rickfernald3452]

check the motor mount on the driver side, they are prone to going bad, that would let the engine lift and rub the wire harness.

[@PatPrice123]

I have 2x 1997 GMC Safaris , same symptoms, one 1 at 150k miles, the other at 199k miles, I have not been able to figure it out, will take a good, hard look, think this could explain a multitude of things I have been putting down to "old age". Thank you.

[@lunkerjunkiestv186]

We are going through the same thing on an 02 s-s10! Excited to check this theory out on it in the morning!,. because we are about to take a stick of dynamite to this thing!!

[@crazee6821]

Did you figure out your issue ? I’m also having a major issue after changing $15 grand worth of parts and transmission

[@Durango1999chm]

I had very similar history many years ago, replacing similar components, now chasing cause for two backfire like big band events.

[@fordham64]

That's crazy! Can't believe you found that.

[@jeffcotton2120]

I’m seeing the same problems on a 99 Astrovan while changing a lot of parts. Including stalls while driving, but that can also be a rusted, corroded, dirty or damaged distributor causing the magnetics Operational Effects to cancel inside it at higher temperatures. And it doesn’t throw a code. So I replaced that too. Nice reminder about needing to check the wiring systems on these, I see some additional problems there also. Especially in compact tightly packed high temperature operational areas & moving pressure or friction points.

[@tommychong9735]

Great video I will definitely have my wire harness checked tomorrow Thank you

[@cornelieusfields2062]

First rule of thumb when you have a miss is you check your wire harness. You check your spark plug wires. Because it's going to be electrical. then you go starting replacing parts later on if you discover one of the parts are bad. Even in your manual it'll tell you check your wiring first

[@scottymizzo415]

thanks for that one I will take a look and see that wiring harness good place to start

[@bigticket5869]

WOW. What a PITA to figure out. Great work!

[@nataliebarth2016]

Great job on fixing that vehicle! You are awesome! A real professional! You're lit.

[@dodgeplow]

I have an '01 Jetta. For 5 years I would intermittently lose my AC compressor function. Checked compressor, pressure switches, dash switch, fan relay (it's all routed together), etc. fan temp switch, ambient temp sensor etc. I tell my tech I'm frustrated with the problem so just change anything that was still original. He goes to check the fan/radiator temp switch and compressor kicks on. There was hidden corrosion back from the terminal. Road vibration would make the circuit open and close at random. fixed that wire and I've had no trouble for past 10 years. what a hassle it was dealing with that.

[@stephengordon8968]

Wow thats a good find ! I'll watch for that one

[@paulinofernandez3759]

Thank you I have the same problem in my 02 astro van

[@user-gj4ei6dc5q]

Good find. I really don't like shit like that either. If I had thought about it when I was 15 years old and started working on vehicles in a shop back in 1988 and wrote down all the goofy crap like this that I have repaired, it would be an encyclopedia. You obviously have the patience, determination, dedication and knowledge to call yourself a true professional. You and I are the type of guys that have forgotten more things about repairing automobiles than most so called mechanics will ever know. Just in writing this now is bringing back so many memories of silly shit it's making my brain hurt. Good job and don't ever give up! We're among the last of a dying breed.

[@toddambroziak4751]

Thanks man I really appreciate that! It's always gratifying when you conquer a hard one like this. I figured I'd share with everyone because I'm sure there's another van out there with the same issue.

[@ChaplainMike777]

Thank you for the good detective work. I will keep that in mind!

[@tomd720]

Good detective work. I will check my 2000 astro for a similar problem.

[@lowellmayfield5736]

This is 100% what is happening with my 2001 Silverado 4.3L!

[@u.s.a.198]

4.3 Tip to share. I had a strange stalling, skip issue and no codes. Couldn't figure it out. Thought it was the fuel pump. With the engine running I pressed on wires and hoses looking for a vaccuum leak.. I pressed a wire and the engine shut off. Magic moment. The coolant sensor connector plastic stay tab had broken off. The coolant sensor plug was half in half out. I inserted and it started right up. I removed it and it stalled.. crazy issue to locate but I wanted to share with others.

[@basictechreviews]

You just confirmed my suspicions, thank you

[@Paul-sh4on]

EXCELLENT VIDEO MY FRIEND...4.3 ENGINE RUNS GREAT WHEN DRIVING BUT IT MISSES ABIT AT IDLE AT THE LIGHTS OR STOP SIGNS...REPLACED ALL WIRES PLUGS AND ROTOR AND CAP...AND NOW I CAN NOT READ THE OBD NO POWER GOING TO IT

[@LetsFigureThisOut]

Try cleaning the idle air control valve. Both the valve pentle and seat in the throttle body. If you can afford it, just replace the valve while you are in there, but make sure you clean the seat

[@2Jeezuzisreal]

My 2002 5.7 gmc van misfire 2 years got so bad could not drive. 3 mechs gave up. It only misfired only when i reversed it. Then forward it gradually got worse as a drove. On highway Blinking engine light. As time passed i had to park it. Tryed new Distributor kit . New plugs wires. New spider injectors. I got broke and the Auto store rich. Sold it..

[@bcbp14]

I had the same issue with an 01 Lincoln Navigator. Went crazy chasing same cylinder miss and just started wiggling shit until I found it.

[@miguelbalderas1731]

Thank you I have a misfire on my 2005 Chevy Astro I’m going to check the harness

[@workingshlub8861]

this is one to remember....i love thee vans but they do shoehorn everything tight..pain in the ass sometimes..

[@scottmcintosh2988]

I lived 100 feet from the ocean lots of pea soup fog spray WD40 inside distributor cap W D means water dispersment works great !

[@OKBAOK]

Thanks I got 2002 Astrovan good Info for me to check in case. Thanks for the video👍

[@andypeterson2126]

Underneath your distributor there is a metal shaft connected to a gear of some sort. That gear is what is broke and is causing the misfire. At least that was the problem with my van. Anyways I took it to the dealership and they didn’t know what was wrong with it. I wound up taking it to a really ghetto Chinese mechanic shop and Voila they figured it out! And they fixed for for only like $180!

[@jrea424]

Someone didnt watch till the end.. He found a rubbed through wire

[@mksmoksmk7083]

Only the Great ones Lose Sleep, Great Job my Dude!

[@bb8215]

Thank you for this! I have the same problem and will check it out. Thanks!

[@michaelsnyder9422]

Thank you I have the same problem in my 2000 safari random misfire and I can not for the life of me figure it out.

[@marklennox2151]

I guess I'll have to check this too. My 2000 Astro just had a new Jasper engine and all the rebuild kit installed but it misfires badly in wet conditions. It's driving me nuts.

[@oby-1607]

They pack 10 pounds of shit in a 5 pound bag. lol. Yeah, vans are always a murder to work on but I have a GMC Safari cargo and I love it. I am not a GM guy but this one makes the grade and If they still sold them new, I wouldn't hesitate to buy one. At least now, your van has been all tuned up.

[@mustang23201]

Very proud of ya guy!

[@propellerhead9197]

Thanks good job. It's not always the obvious..

[@carcasscruncher9354]

I have a 2002 chevy astro 2wd. A while back I was getting transmission issues with the solenoids. It only happened when turning right and going uphill at the same time. I figured it was electrical after changing solenoids out and what I found was a yellow wire chafed through the harness on passenger side under doghouse. It was a pretty easy fix. But now I have this misfire shit happening again. It seems like the distributer caps only last about 3 months and need change out again. Pretty ridiculous because I have changed it out probably 13 times now. It wasnt an issue until the past 3 or 4 years and now it's all the time. I'm going to look for something that a chafed wire again now.

[@richardrandall1852]

get accel cap n rotor!!

[@carcasscruncher9354]

@@richardrandall1852 did that. Wasnt the issue.

[@carcasscruncher9354]

I have a 2002 chevy astro 4.3. Kept getting a p0300 code and a code for solenoids. Changed the solenoids out and still got that code. Found a bare wire that was grounding out under the doghouse. Yellow and black if I remember correctly. Still have the p0300 and a p0138 now. I changed the plugs and wires and cleaned up the distributer cap. Ran great for about 400 miles. Now it bogging down or misfiring between idle and 20 mph. Pretty sure it's going to be another bare wire now.

[@OKBAOK]

Hi any update on your van now? Thanks, we have the same year on the van 🙂

[@richardrandall1852]

Rodents ?

[@carcasscruncher9354]

@@richardrandall1852 idk, maybe. The wire that was grounding out wasnt from rodents. It was from rubbing on the frame while turning right. Pretty sure it's the crank shaft sensor for this problem but havent had time to do much with it. Got a new van so the old one just sits there waiting for some TLC. Lol

[@emersonmcnamara517]

Todd,Todd Oh Boy had to Stop Video lol @ 10 lbs In A 5 lb Bag!!! Epic Dude ...

[@OKBAOK]

One good tip guys causing misfire on this Van if there’s a wiring issue or grounding issue is.. While the Van is idling rock the Van up and down also open the hood then slam it very hard while closing it while doing that test, listen for change of idle sound or engine sound..

[@saulluciano2263]

Thank you very much for your nice video I will check my van tomorrow

[@davecavender8534]

That's was a good shot !

[@davidrenteria7343]

Thanks buddy I appreciate your video

[@ldubel5922]

Way to persevere bro!

[@raulaviles6227]

nice found thanks for the video hi from oaxaca mexico body

[@bb8215]

That was it! Thank you!!!

[@scottymizzo415]

just to make sure you fixed the bare wire and now the car is running smoothly ? just from that one wire or was there several wires that was affected ? pleas let me know

[@JV_214]

I just bought a 98 and have a multiple miss on all cylinders, I don't believe it's the engine as it sounds like an ignition miss,.I haven't thrown any parts at it but will start with inspection of the harness

[@badassblue1]

Having the same problem I can move the harness above air intake it will start running funny I will start looking in the morning thanks

[@josegracia6749]

Gracias por la information

[@jimtoohey7242]

My blazer doing same thing and ac clutch kicking on and off like a mf. Just bought it 130k mi. As soon as i pulled the pass under load ses blinks and light popping sound loss of power. Ty good video!!

[@brensdaman926]

Did you ever figure out what yours was?

[@waynebastianelli8391]

Good one that's F^#&up great video

[@marklennox2151]

I swear I hope this is the issue with my 2000 Astro. If I see my fuel gauge bouncing around after I start the van I know I'm in for some misfiring. If its bad I smell something electrical. I also hear some clicking that sounds like sparks where your problem was. Is there a new harness that I could buy?

[@Mikecianfrocco]

Im checking this tomorrow!!!!

[@ryanhenak]

You're a savior!

[@ralphchavez9316]

Great information. Thank you for sharing , now go take a nap and get some sleep.😂😂

[@Wgh466]

2000 blazer missfire was timing cover seal was bad .i use a smoke machine and walla. Fix the problem.

[@WayneBastianelli-fb6jx]

Voila! Sob omg wtf I'm with ya all the way yep harness same spot same shit I put foam black around it 2dollar fix

[@tradmanmike3360]

GREAT VIDEO OF REAL HELPFUL INFORMATION! UNTIL YOU SHOWED THAT WIRE, I TOO WAS LIKE WTF!!!

[@jakeday4105]

Hey Todd what's up buddy I have a 2004 Astro and it only misses in overdrive what do you think that is sometimes when I'm going up the hill I have to put it in third and it doesn't miss in 3rd

[@garylivingston9052]

So did you tape the wire up or splice in a fresh piece?...thanks

[@BrantFord-lx4xe]

nice work!!!!

[@richardcopeland3982]

I have a 02 s10 4.3 same thing changed everything even the ecu an mine will throw a po304 random misfire my pipes are turning black so I'm thinking I have a harness problem now as well

[@carlkraus6034]

I have 2001 Jimmy 4.3 L and it misfires random under load or high revs. I give up. I am not going to get the parts cannon out and shotgun this POS. I will keep driving. I may change the cap and rotor but that's it. My blazer had the same problem Also during damp or high humidity times. I did notice you never mentioned replacing the ICM. I might try that.

[@peterhatch1583]

It just great for this sharing thks

[@kf5435]

You didn't replace the manifold first??????? Lol

[@brensdaman926]

My 2000 Blazer is doing the exact same thing! Should I check the main wiring harness from the PCM to the engine?

[@brunorios7223]

wondering how much wiggle is acceptable in distributor. i have changed one before but paid no attention. mow got a 99 blazer knew spider bad. changed that, wires and cap rotor. still similar misfire but not as bad. a bit of twist back and forth on distributor.

[@scottjacoby763]

Hey Todd. Do you still do side work. I have a 2011 Ford Fiesta and need to have the TPMS module programmed. I put in a used module and now have a VIN mismatch. I’m having a recall done next Wednesday at 2 PM at Schmit Bros and wondered how much you would want to flash the module for me with the IDS?

[@markschmalenberger8301]

I had a misfire at idle 2years ago. I replaced plugs wires icm, cap & rotor. No change but while driving without the dog house i noticed the engine moving & shaking along. I found & replaced the left side engine mount. Problem went away,now 2 years later misfire came back. While driving without the dog house I see I've got another broken motor mount. This is crazy but I wonder if vibration of the engine hitting the frame could be triggering the knock sensor? I haven't replaced it yet due to weather but am crossing my fingers.

[@toddambroziak4751]

I think that the motor mount being weak on my vehicle was probably the reason why that engine harness shorted out due to the engine lifting when in drive causing a short to ground against the AC line.

[@nnnnnnnnnick5557]

I have the exact same problem except mine is an 05. Looks like they secured the wiring harness a lot better... This makes it harder for me. I replaced the cap and rotor several times. Spark plugs, spark plug cables. Engine timing chain (lol)... Spider injectors... Still same exact problem.... Help me

[@wolfgangzeisig6313]

thank you very much.

[@86jekstrom]

Good catch outta left field... If you don't have a nick name I'll call ya Ken Griffey Jr😮

[@drivechile3306]

did you change the whole harnes or just isolated and soldered the cable?

[@73fomoco]

Tank god hey! Go git sum sleep now one time!

[@adventureswithdougie]

Never did find out the problem and sold the van.