P0410, P0300 Secondary AIR and Random Misfire Diagnosis Pt-2

In Part 2 we diagnose the P0300 random misfire code on the truck.
Part 1 is here:
• P0410, P0300 Secondary...

[@DJDevon3]

You saved the owner $700 for the non-issue air pump plus additional fleecing that would surely come thereafter. Saved that owner at least $1000 minimum due to a lazy mechanic. Excellent diagnostics!

[@richardfitzwell727]

Thankyou for your in depth diagnosis series. I admit I'm a parts changer, hoping to solve the problem. Due to my lack of understanding of how to properly trouble shoot to determine a problem . Please keep doing this series.

[@dewaynemaiden]

Me 2, even if I throw a couple of parts at it, I'm still way ahead, I haven't paid a mechanic to work on any of my vehicles in over 25 years.

[@trainer2018]

Good job Matt, I had a similar experience once myself with a dealer tech misdiagnosis on a Plymouth Laser that had a coolant temp code and a hard start when cold, did not have my own scan tool at the time, but when the new sensor didn't fix it I ponied up to get coverage for this vehicle with my scanner and saw that the computer thought it was negative 20 outside when it was 70 degrees, tested the wires and it ended up being a bad computer, don't think dealer Techs are bad, I think sometimes they feel rushed because they are on flat rate. Know quite a few awesome dealer techs.

[@jeffreynobles948]

I think it's pretty safe to say that the shop the customer took it to, to begin with didn't do any fuel trim testing. As you pointed out, if a competent mechanic was working on the vehicle, and had looked at the fuel trims (as was stated), he would have known that 24 for an LTFT on both banks is indicative of a serious issue. Personally, I don't know what to say about that either; other than WOW!!

[@ashleygomes7589]

Really enjoy your shows,’ it helped me out sooooo much,’ thank you.

[@luisaliceaortiz7791]

Thank you for teaching me this morning stay blessed

[@whitetiger8652]

Excellent diagnosis Matt, I own a 2003 Chevy Tahoe 5.3 eng. with 84000 mi. and I am sure it is a matter of time before I will be replacing the intake manifold gasket.

[@happyasahippo8597]

Hi Matt - Thanks for another excellent video showing a systematic approach on car diagnostics. I always found the 'let's change some random parts and see if that fixes the problem' approach awkward. As an engineer in software development, I am simply used to doing extensive diagnostics before changing the smallest bit in a system. I never change something in a software if I do not exactly know, it will fix a bug. So - I really appreciate your philosophy to first really know what's wrong before changing any part. Your videos give me a better understanding of the control systems and loops and the different subsystems and mechanic components in modern engines to allow me to do a systematic search for the root cause of a problem by thinking on my own. Therefore I'm really looking forward to your next 'understanding XYZ' video...

[@SchrodingersBox]

Much appreciated and glad you "get it". Most people by far (maybe 98%) still don't understand this approach- but I don't make videos for them, I make them for people like you.

[@williamestrada3141]

Love your videos. Love how you explaine step by step. So easy to understand.

[@SchrodingersBox]

Much appreciated!!

[@elvincamacho3621]

Thanks Matt that the right way to Diagnose thank you

[@dogbyte555]

This is good stuff. I have 3 of these engines. Thanks.

[@chadchiasson7768]

Thanks for the video. Instead of introducing a air leak, when checking for O2 response, turning on the A.I.R. System would be a good test ( if equipped). Never heard of the A.I.R. System before today. Always learning. Thanks again!!

[@SchrodingersBox]

Yes indeed. Often I will do that using bidirectional control as part of O2 sensor testing!

[@russelldilworth1784]

I have to laugh when I read some comments here..I think a lot of people after watching this video. .think this is exactly the same problem they're having! !!!..Then throw parts at it expecting to fix it! !!.. cos I know MATT hates that approach. .. As Matt clearly shows. .diagnosis thru a process of elimintion is always the best way! !. and of course double checking the fix for the immediate CAHANGE!!!..BRILL VIDEO'S MATT... New subscriber!!!

[@p51302]

Excellent two set video.

[@jbpost52]

Matt, I had heard that Nissan had a problem with either the intake or exaust manifold gasket leaking when cold because of plastic gaskets. But they supposedly would seal once warmed up. That intake manifold is not plastic as well is it? I think it was Scanner Danner who said that the problem becomes evident by the model of the car, but it wont be leaking once the car is warm. I have been taking his on line class, made it into the second week, a bit complicated now on part six. Hope all is well with you.

[@Sk1ds87]

Can I also use a mixture of 30 % propane / 70 % butane to find leaks?

[@melissaspeck1251]

? If your air pump is not working could you see a P0300 random misfire or would you shoot for the intake manifold leak? Thank you your video help.

[@juanayala9093]

i have a 2005 mercedes c320 and need help while having the the car in idle i took the two check valve covers off and notice that one side dose nothing driver side and passenger side you can hear it and smell exhaust and feel air pressure coming out dose that mean i have a clogged heads

[@genehensley767]

Very nice your definitely a sharp and funny cookie .

[@guidosalas7089]

Excellent video. Thanks

[@SteveRobReviews]

Fantastic Matt - on my 6 liter that was an intake vac leak there was no codes or out of range trims. The odd thing was it only exhibited a rough start and stumble at below -10 deg. C and before it got to CL it then ran fine. As for the cat inefficiency code on the Tahoe I have experimented with a $5 fix that seems to resolve the problem in quite a few cases using spark plug anti- fowlers attached to the downstream O2. The last one I did was a 1998 suburban that was emission tested at the tailpipe and it passed. It's been over 2 years now and the code never came back. Worth a try on the Tahoe.

[@SchrodingersBox]

Yeah the folks have got by last couple years with the bad cats because it still passes "speed pass" but eventually here you will have to take it in and even the check engine light alone will cause a fail. I just happens I just finished another car with P0410,1415 and 1416 today- this one also showed rich response when you activate the pump. Turns out both check valves clogged with carbon completely- no AIR to the manifolds, similar to bad control valve or solenoid not opening. Took all of 7 or 8 minutes to diagnose since I'm pretty well familiar with AIR after having 3 cars in a week now with AIR codes!

[@SteveRobReviews]

The new testing up here also fails you for just a check engine light on. The anti- foulers seem to work at keeping the mil off . If the truck comes back give it a try. Did you use new intake bolts and isolators, I didn't , holly crap I couldn't get the old ones out - it was -15 out in the driveway and It didn't look like I was going to get another warm day - so I put a little thread-locker on them.

[@SchrodingersBox]

Steve Rob On these plastic intakes, the torque is only 89inlbs so I do not use new bolts. I just chase the threads in the head and bolts is all.

[@SteveRobReviews]

www.motor.com/article.asp?article_ID=2139. I used loctite 243 blue , I did not have the primer for red and didn't think red would be a good choice if I had to go back in, seems I may be wrong. Instructions do state to replace the bolts as well because they do have threadlocker pre applied, but i have not heard of any problems with the LS intakes coming loose using the old bolts or not using threadlocker. Sure would like to know for sure since I am now way an expert.

[@SchrodingersBox]

SATAMAN Schmidt Not correct- these model's intake bolts come with rubber (urethane actually) "compression" washers that do not require locktite. Red locktite would not be a good choice because the bolts are very thin and red locktite would be risking twisting the bolt off on next removal. I sometimes use blue loctite if I think it necessary when the bolts do not have lock washers or compression washers. I actually never use red loctite for anything in fact.

[@salvadoralvarez279]

Muy.buen.trabajo.profesor eres #1

[@berkmanyt]

Comment below per 2nd watch….I watched you Autotap vs Ingenuity comparison…I'm sure I'll be repeating watches…esp the fuel trim videos. How much more comprehensive is you subscription channel video ? Thanks again

[@mosesdog2]

Fantastic video.

[@charliethorne1255]

Man you are good!! You may have even led me to my fix!! I have a cylinder 8 misfire and can't find the cause of it to save my life😂

[@nickwilson1476]

Nice work!

[@martinarrieta7779]

grasias por toda esa informacion excelente esperamos mas videos tan interesantes como los demas

[@SplashphotoCM]

Matt, I'm getting a PO171 code which after a while kicks in a PO300 code. Had the intake and both knox sensors and wire connector changed due to a 320 and 327 code. Those codes came back in a few days. 2003 chevy tahoe 4.8. I changed the PCV valve which was really dirty. and the 171 and 300 went away for a few days and came back. My tahoe starts and runs fine when cold but codes kick in well after warm and driving. Runs great for two days, no codes then bad for a couple of days, 221,850 miles on her. Also intermittent 1133 and 332 codes but always go away after I clear them. Live in SoCal.

[@SchrodingersBox]

What data do you have? Specifically, what was the data you got that lead you to suspect the PCV valve? Was there a negative LTFT? I would start there.

[@sam111880]

curious what software is that on your computer and how does one get that program. Is it a free download or did it come with a kit that you payed for? I can connect an odb2 to a laptop with a usb to DLC connector or serial port to DLC connector but was curious about what that software you uses is... seems pretty much has everything in one for sensor information

[@jeffreywilsonrubikscubeonb2428]

Awesome vids Matt… I have not been on in a while to watch but just watched this 2 part series. Congrats on 10,000 subs and 1.5 million views buddy! I am actually glad I have not been able to watch in a while because now when I have some time I can do a bit of binge watching!!! :) Happy New Year brother!

[@SchrodingersBox]

Jesus bro where have you been???? Glad to see you are back and I hope you will catch up! As you see things have been going quite well lately. Glad to have you back bro.

[@jeffreywilsonrubikscubeonb2428]

Schrodingers Box Lol my career with Snap-on Diagnostics keeps me on the road A LOT. It has been a crazy ride for the past 6 months to be honest. I love it, but have a lot less free time :) Having 3 kids takes up most of the little free time I do have now!! When I was home every night as a technician it was much easier to keep up with the vids. I managed to watch 3 so far today thanks in part to the 38 cm of snow we have had dump on us here in the lovely interior of British Columbia. I look forward to getting caught up!

[@satamanschmidt3428]

Jeffrey Wilson Wait a minute. Here Matt's begging for a scope and you work for Snap-On Diagnostics. Can't you get our boy a Versus cheap or at least a Vantage Ultra. Help a brother out Jeff.

[@rickolivasone4790]

Great fucken vide. one of the best i seen so far. thanks for your time since im having an issue with my 2000 yukon with a p0300 and it has been jerking once over 55 milles with the p0300 the only code that shows.

[@SchrodingersBox]

Great- now you can collect data and see if it's induction, ignition, or fuel related so you can fix it!

[@CraigMullins1]

Curious if you have any advice on my Secondary Air System Monitor smog readiness not "setting". I have a 2001 V8 chevy silverado. Put about 5,000 miles on it. still hasn't set. I never had a check engine light come on since I owned the truck. Anything in particular I should look for? Can't seem to find any issues...

[@SchrodingersBox]

Test the system verify operation via fuel trim analysis and if it works then if may be a communication issue with the scantool not showing the system is actually setting when it is. Also look up to be sure you are doing the appropriate drive cycle pattern to initiate the self test.

[@chrisvantuyl5554]

Yes sir. Great video. I've had this code on a 01 S10 4.3 liter that has been impossible to fix. I have a freeze frame of data and would like your advice to steer me in the right direction. Could I email the information to you?

[@berkmanyt]

Matt…just subscribed…could you do a video identifying the tools you use . Computer, software, multi-meter…etc. Also per improved gasket…Victor ---REINZ …a brief printed id would be extremely helpful to us non-fulltime (sellers) repair people. Thanks..a great step by step demo…and skipping the bolt off / bolt on is GREAT….no need to show how to turn the wrench. Thanks for a GREAT video ! walt

[@SchrodingersBox]

+berkmanyt I do have videos on my scantools I use, my oscilloscope, and the IAT and Nissan O2 sensor videos demonstrate power probe equipment I use. Other than that- almost nothing I have is specialized.

[@jasbierkandola5736]

Can you tell me which diagnostic tool are you using please

[@Handinerd]

Excellent video and mechanic skills. Experiencing almost similar problems with my 01 jimmy except I'm only getting misfire on cylinder 3, could i have the same problem with the gasket? Also note it seems to get worse as the engine warms and sometimes I feel the power temporarily increase then slug back out. Any advice would be helpful. Thank you

[@SchrodingersBox]

What data do you have?

[@Handinerd]

+Schrodingers Box I'll run diagnosis and get back to you asap.

[@ThunderAppeal]

All pretty good stuff. I guess buying that MotorAge ASE training kit was worth it.

[@berkmanyt]

Were you using your Ingenuity scan tool here ? Thanks walt….GREAT DIAG !

[@markusdd5]

Thorough as always...and that glove middle finger made my day...xD Happy New Year from Germany, and keep the good videos coming! (and that DIFFective made my brain melt...even as a non-native english speaker....)

[@SchrodingersBox]

Hahaha if you read that shop's quote there are about 5 misspellings in it! Happy new year my friend!

[@markusdd5]

Schrodingers Box I'd overlook that if they were able to fix my car, because that's their job. But now you can't even tell them to become a writer or librarian instead...what a bummer Haha By the way I have an idea what they might have done when they looked at the fuel trims and then did fuel pressure testing...maybe they thought 45% was too low...so the engine couldn't get enough fuel. It's hard to think that stupid as a "professional", but might be an explanation how they overlooked this very very obvious problem^^

[@SchrodingersBox]

Markus Krause ROTF at "I would have forgiven the bad spelling if they fixed the car" Hahahaha so true!! Nice one! Who knows what they were thinking. Actually the fuel pressure test is a reasonable move for a P0300, and low fuel pressure would certainly cause high fuel trims, but not under idle like that, and the misfiring would get much worse under load instead of better. All I can say is I don't doubt they looked at fuel trims, I just doubt they knew what they were looking at when they looked at them lol

[@satamanschmidt3428]

Schrodingers Box What everybody fails to realize is that the word professional simply means that the person gets paid to do what they do. It has nothing to do with competence. Taking your car to a dealer is no guarantee of competence. My father made the following point to me when I was very young: For every doctor that graduated at the top of his class there is one that graduated at the bottom. They are both given the title of Doctor but it's up to you to figure out which you want to operate on you. Same is true of auto mechanics.

[@markusdd5]

nice picture ;) In case of a mechanic though other constraints also play a big role. Things like Flat Rate Systems don't help. Some of these mechanics are changing parts not because they don't know better, but they have to sell parts for the dealership to make money...and changing a part is more profitable than a proper diagnosis. If you were wrong...next quote for the customer...and the next part...and more money. So just a word for the professionals here...I think there are more good mechanics out there than we think...it's just they often cannot work like they would under better conditions for themselves.

[@mdupree5858]

Hey just subscribed. What computer diagnostic program are you using, can you recommend any others. Great Video!

[@everardocamacho5063]

hi matt, by using a propane to find a intake or others leaks is not danger? that may cause a fire? please let me know, I like all your videos.

[@SchrodingersBox]

+Everardo Camacho No it will not.

[@vicchang3538]

Thank you that was usefully educational, but I'm not sure if I understood what "freeze frame" indicates? Put it in the freezer or lol?

[@SchrodingersBox]

Lol. Freeze frame is a capture the computer does of the sensor outputs at the instant the CEL lights.

[@bradleypatrick79]

not sure if you've done one but would a review of obd scan tools. I have a Bosch 1300 but not sure to read some of it. what should my readings be abslt tps, calculated load, ect be reading?

[@SchrodingersBox]

it all comes from understanding the systems, not from memorizing specs. When the systems are understood the readings can be interpreted based on the conditions at time of reading.

[@satamanschmidt3428]

Matt, for your information the problem with the intake manifold gaskets is caused by DEXCOOL. It turns out that DEXCOOL eats plastic, which oddly, when this new coolant was first introduced by GM the GM engineers KNEW that it ate plastic. Nonetheless, the material the carriers of the intake manifold gaskets were originally made from was plastic. On the 3800 aluminum carriers were used to fix the sealing issue. According to what you said they used steel on this engine. Amazing that the plastic carriers are still available considering how well know this issue is.

[@PhattyMo]

I ditched Dex-Cool in favor of the regular old green stuff. First you must drain the Dex-Cool and flush the system REALLY well,refill it with plain water,run it a while,let it cool,and flush it again. (-this is important,the two types of coolant do not play well together.Make sure ALL the Dex-Cool is removed.) Finally,refill the system with the regular green stuff (50/50),and make sure to bleed it well. Along with new metal intake gaskets,and rubber vac lines I haven't had any similar/major issues on this 3800S/C yet. *knock on wood.*

[@SchrodingersBox]

This is a complete myth- dexcool absolutely does not eat plastic and no GM engineers thought this and did so anyway. I hear this myth all the time. The evidence for this being a myth is apparent in models with plastic manifolds (like my trans am) in the same era that also use DexCool but never had intake leaks. Besides, on this model you can see this is a "dry" design anyway- the coolant never touches the gasket on this model. Anyway The real story is, originally GM technicians were getting lots of the 3800/3400 (ONLY these engines btw) internal coolant leaks and when they went to replace the gaskets, within a year the customers returned with the same problem. They thought that Dexcool was eating the silicone sealant on the gaskets (because not being chemists they didn't realize this is not possible). Eventually is was found, because the leaks almost invariably occurred and even recurred in the same area, there was a design flaw with the intake manifold itself. A TSB was issued sometime around 2002 by GM to use a specific aftermarket gasket (I forget which one- I have done enough I should remember by now) in the repair. The gaskets had much thicker sealing silicone material but were STILL PLASTIC (thus confirming the myth about dexcool eating plastic). The new gaskets proved to be permanent fixes and in fact any time you get a new gasket for a 3400/3800 whether plastic or steel, they will be the redesigned type. But they are still plastic for the basic gasket with works fine, as long as the intake manifold hasn't warped, in which case the thicker steel gaskets work better.

[@satamanschmidt3428]

Schrodingers Box Matt, on the GM 3800 the problem is NOT the upper plastic intake manifold gasket which is called the plenum gasket. The gasket issues attributed to DEXCOOL were with the Lower Intake Manifold gaskets which when they failed caused hydrolock. The upper intake manifold gasket is to this day only a plastic design with silicon seals. It's the lower manifold gaskets which have the aluminum upgraded replacements.

[@SteveRobReviews]

Wow Matt your sharp as a tack . I was at Gm at the time and It's amaizing how our supplier at the time was havoline up here in Canada and it also went into Fords as well with a different dye package. All antifreeze does get acidic over time but on a LS , not relevant. The introduction of ethanol into the fuel has also had an effect on gaskets that were never designed for. On mine I could see the deteration of the gasket not just the compression of the gasket material. I used the same felpro gaskets as well, it came with a EGR gasket and oring. It's amaizing how misinformation can unknowingly be obsorbed for generations, Now was there really weapons of mass destruction or not, LOL.

[@jeffreynobles948]

Great videos. I'm just curious why you weren't looking at the short term fuel trims instead of the long term fuel trims when inducing propane into the intake manifold area?

[@SchrodingersBox]

hmmm if i did that would have been in error- short term would be the way to do it

[@ethanhag]

I have a question... My car when accelerating or right after accelerating, seems to suddenly decelerate (and pull me forward for a second), then continues on like normal. I'm trying to diagnose it, but I have no idea. Maybe an o2 sensor? It sometimes stalls and has low idle at times as well, but works beautifully otherwise. No

[@SchrodingersBox]

What days do you have? Why do you suspect O2 sensor? What was the O2 sensor data output that is making you think that?

[@mtrltoolman]

fantastic diagnoses video matt i love these videos i have some questions about your obd2 scanners abilities . can you read ABS and SRS codes with any of them and which one is ? i need a good and low price scan tool with no extra charges for extra abilities and can read misfire counts .

[@SchrodingersBox]

As you have seen I use two scantools- AutoTap and AutoEnginuity. Autotap will not read either ABS or SRS however Autoenginuity can not only read them, but reset them and in fact on ABS on SOME cars can even do various functions like reset YAW sensors and such. If ABS/SRS is important to you, then Autoenginuity will be a consideration but remember, the bidirectional functions don't work on all vehicles, You will need to contact tech support to be sure. I can tell you I have been able to YAW zeroing on most every GM and Toyota I've encountered thus far.

[@mtrltoolman]

Schrodingers Box Autoenginuity looks nice tool to have . i was using a bluetooth ELM 327 and toyota Tis techstream with no satisfaction because they are fake and they have limited abilities. thank you matt and happy new year .

[@jtravis711]

Hey Matt, watched your video and it was very interesting. My issue is PO300 with idle change after warmed up. No other codes. So I have gone the expensive route of process of elimination. New plugs, wires, coils, knock sensors, cam sensor, MAP sensor, new injectors, new fuel pump/sending unit, replaced intake gaskets and thoroughly cleaned the throttle body. So the 2003 5.3 starts right up but after running for 5-10 mins and normal operating temp. the idle drops to around 525 rpm and gets rough. Any ideas to help out? Thanks, Jeff

[@SchrodingersBox]

What was the data you had that indcated those parts were all bad? I am not seeing any logical process here. What would be a reason for replacing knock sensors for example- was there a retardation of timing- if so how much?

[@davidjohnson372]

jeff what was wrong

[@JeremyDN]

Have a P0300 on my 2007 Tahoe and this is a very informative video. I just wish I had all the tools you do so I can repair it myself. Mine is also giving me a very loud ticking or tapping sound when you try and give it some rpms. Engine shakes very bad but was driving perfect right before it did it. Can you check for intake leaks with carb cleaner as well?

[@SchrodingersBox]

Yes you can. If it's an intake leak you'll have a notable idle increase with carb cleaner.

[@JeremyDN]

+Schrodingers Box appreciate the quick response. Nice to see a mechanic who actually tells people what is wrong and doesn't blow smoke up their butt.

[@JeremyDN]

+JeremyDN just did a quick test on my coil packs and when I unplug number 1 with it running it doesn't affect it at all. I just replaced that last night to along with the spark plug. Guess need to check the wire now.

[@SchrodingersBox]

***** Why would you replace the coil pack? I don't register with that at all. What evidence was there that it was bad?

[@JeremyDN]

+Schrodingers Box was dumb and listened to the guy at the parts store. Was looking for hopefully a quick fix but yeah, I'm leaning towards my exhaust valve is burnt now. My exhaust is sucking back in with every other cycle. Number 1 punched a lifter a few years back and I don't think they looked at the valves at all. You can smell the gas really bad when it idles.

[@roadstar499]

Great job! i have a po300 on 2001 blazer . Plugs were black( running rich)..i did the smoke test and zero leaks... i did plugs,wires,cap and rotor,timing chain, fuel filter and since it has 198k i will be installing a new spider fuel injection system... also replace maf sensor... this is my truck i bought and for every code my cheap scanner gave me i have replaced those parts...the other codes all did not come back except the po300 ....i also watched another youtube mechanic replaced the distributor which fixed his issue... his old distributor was fine looking he said,but replacing fixed...so i also ave a distributor on the way... my truck runs horrible... can you think of anything else i may be over looking? thax again

[@SchrodingersBox]

I am not following- why would you change the MAF and install a new spider?? What data are you basing this off of?

[@roadstar499]

@@SchrodingersBox I had 2 maf codes(po102,po101) come up first...now i just get po300... i am low tech just have code reader... i am doing eveything i can think of... it runs horrible... One day i hope to buy a decent scan tool and learn how to use.. thax

[@sara78130]

good job

[@cholochedd6752]

Where in Denver are you located brother I desperately need your help to get my 03 suburban fixed it last ran rich and would misfire and cut off then this last time it happens never started up again I can smell fuel when trying to start and it backfires and seems to either get to much fuel or not enough vacuum idk but I live close to Denver I'm desperate

[@SchrodingersBox]

Highlands ranch

[@alanreyes24]

lol nice joke about the glove, it was funny!!!! what's the name of the smoke machine that you used to check for vacuum leak? I would like to buy one like yours

[@megans.427]

i have a 02 chevy suburban 5.3 withl460 trans works perfect somtimes then it will have long shifts and sometimes there is is no one home in 3 andoverdive redone all clutchs eletronics have you come across a problem like this?by the way your awsome watch some of your videos dam your good you made me understand thanks

[@SchrodingersBox]

Something like this would normally cause a check engine light- are there any codes?

[@konstantinusstoyanov9749]

Great tech

[@nealjag3917]

what scan tool are you using

[@kennyalan8103]

Talked to you a while back... living in Costa Rica and rebuilding my 94..Toyota 4.5L 1FZ-FE 6 Cyl. Land Cruiser... Well I was torque-ing down the Head... and I forgot the DAMN.... FLAT WASHERS THAT GO UNDER THE BOLTS...! Stupid or What...! Do you think I have to pull them... order a new head gasket or just leave them be...? Thanks Appreciate your input..! Wow... Bumbed out..! Ken

[@randalldalton5475]

Love your videos!!!!! Part of my regular diet. :) What make/model of smoke machine do you have?

[@SchrodingersBox]

It is a Cornwell smoke pro that I got of craigslist from a Hyundai mechanic who seemed to me he probably stole it from a shop and used the money to buy crack. But it works great and it is invaluable for detecting vacuum, evap, and exhaust leaks.

[@randalldalton5475]

Crack makes replacing plastic intake manifold gaskets go faster. Gotta give him credit for that. Thanks,

[@dogbyte555]

Awesome.

[@davidhall3747]

Nice to see a True Professional Automotive Technician- not some Glorified Parts Changer.

[@SchrodingersBox]

Thanks but i am actually a DIY not a professional

[@davidnelson8076]

Hi I have just found your site and I think your way of approaching a problem is very professional as I watch this video I could not help wonder what diagnostic software you are you using to diagnose the vehicle I could do with using it my self my name is david and I live in england----- regards to you david

[@SchrodingersBox]

Thanks David- the scantool I use is called AUtoEnginuity. You can search my site for a review of it called "Scan Tools Review for Home Mechanics"

[@genesmay6589]

hope you sent this video over to the diffective shop.

[@dewaynemaiden]

Alot of shops are parts changers and cant figure anything out unless a code reader says so

[@zyou8er]

Hi, can a skipped timing chain cause misfire? Thanks.

[@SchrodingersBox]

it can indeed

[@wtbm123]

But , But ,What about that diffective air pump . Good fix and i like those gaskets too ,and right, wrong or indifferent , I reuse those intake bolts too.

[@SchrodingersBox]

There is nothing wrong with reusing intake bolts- they are torqued to a mere fraction of what head bolts are. The one exception I make is with intake bolts that run through coolant passages- in that case I do prefer to replace them since the coolant really cruds the threads up- but even then, chasing the threads is acceptable.

[@philh9238]

where did you buy your smoke machine??

[@SchrodingersBox]

Craigslist for $600 off some mechanic who clearly retired from mechanic work to become a full time crackhead.

[@fieldsofomagh]

Would it save time to do a smoke test first? since you would have a fair idea from past experience what the problem might be.Those bi-directional scan tools are really the business and cut out a lot of the donkey work. Great video for everyone working at the coalface and is awarded 10 out of 10 for quality and content.

[@SchrodingersBox]

Thanks Tom. I would certainly not argue with doing the smoke test as a first test except that I had no reason to believe the P0300 was the result of a lean misfire until I saw the fuel trims. I fact I was originally thinking the misfire might have been related to the P0410 but the scantool ruled it out. Also, keep in mind I still need the smoke test findings to match the cause of the misfire- for example, if I smoke test and find an intake leak, I cannot be sure that is the cause of the misfire. If it turns out the intake leak causes a LTFT on only 15%, then surely repairing the leak will not fix the misfire- something else is causing it. Thus I always read the scantool first to get a direction to allow me to suspect a lean misfire in the first place. In general, as much as I love the smoke test, I only use it after I have established a direction towards a lean condition indicating it will help find a problem for me.

[@l.c.9596]

great fix, so how much did it cost your costumer to fix his car just for the parts? I know the other mechanic said $700.00 just for the air pump (crazy looser) lol

[@SchrodingersBox]

Total for everything including my labor was $350

[@MrBtine91]

What type of scan tool do you use?

[@SchrodingersBox]

Autoenginuity

[@talonbautista]

I have a misfire on my 2002 Cadillac Eldorado. If I heard correctly, you are located in Denver? Colorado? If so, I would like for you to diagnose my misfiring of my Cadillac Eldorado. This was a very great and informative video, thank you! If you are located in Denver, CO. Can you let me know your address.

[@SchrodingersBox]

Send me a PM with your contact info and I’ll see if I can work something out. Pretty booked through June.

[@talonbautista]

@@SchrodingersBox I'm new to this I don't know how to send a PM, could you send me one first? That way I can give you my information.

[@CHARLIE1955able]

300 code 02 deville, i hear some noise at solenoid location, never heard before while revving engine, this gives me hope, thanks

[@SchrodingersBox]

+yank mcruff What diagnostic data do you have?

[@CHARLIE1955able]

+Schrodingers Box p 300 blinking engine lite, this miss comes and gos, drove yesterday morning with no problem, it came back in afternoon, lot of parts replaced last year, fuel pump ,egr ,mass air flow, cat converter, i will check the pvc hose under the intake manifold, last time it was coil pack, i need a portable readed, i use just the on board dianostic, your new sub thanks you ,,vinny

[@SchrodingersBox]

yank mcruff No i need to know the LTFT, STFT under idle vs load. What is the TPS voltage at idle vs WOT? What is the IAC position? Or at least what was the data you used to determine the fuel pump was bad. What data did you use to determine the EGR valve was bad? What data did you use to determine the MAF was bad? What was the MAF frequency anamoly that indicated it was faulty?

[@2pistolz]

If u have the trouble code 420 ,i recommend using the smoke machine

[@SchrodingersBox]

Hahahaha!!! Nice one!!!

[@2pistolz]

@@SchrodingersBox your video about fuel trims helped me fix my 4.3 vortec v6. i had a long crank time before start condition with a rough idle , no CEL . my short term fuel trim showed -30% at idle , so i went for the leaking fuel injector and found it. the hose to the injector was spraying a fuel stream the size of a piece of hair. i replaced the single injector on the spider, they sell the single injectors on ebay. now it runs great. thank you

[@chrischow7398]

Greetings Matt, new subscriber here! I really enjoy the scientific approach to diagnosis. I have some data that I plotted (STFT, LTFT, O2 Banks 1 and 2) in recent weeks using OBD2 that I would love to have your input on as I have been getting intermittent P0300 random misfire codes. Would love to email and hopefully discuss with you. Looking forward to hearing from you.

[@SchrodingersBox]

Ok what dat do you have?

[@chrischow7398]

Schrodingers Box STFT bank 1 staying steady around 13-15% on idle when car is warmed up. STFT bank 2 is around 10% on idle when warmed up. LTFT on both banks ranges around 4-6% on idle, sometimes fluctuates on different drive cycles on idle. I do have graphs that I would like to show you.

[@SchrodingersBox]

That's not possible. Explain hopw you have 14-15% STFT with near zero'd LTFT please. Are all the fuel cells learned?

[@chrischow7398]

Schrodingers Box yes, those are with the fuel trims learned. I did reset trims and cleared the codes a month ago. If you would like to see my graphs, I'd be more than happy to.

[@chrischow7398]

I don't understand why the LTFT is not compensating the percentages of the positive STFT for the lean condition. That's my question too.

[@satamanschmidt3428]

We've been having this discussion about red Loctite and my use of it on GM 3800 upper intake manifold bolts and I myself wondered why I've had no problems with removing these as everybody seems to think of red Loctite as being as permanent as epoxy. Well look at this TDS for Loctite 263 (which is the best all purpose red Loctite currently available) and the answer becomes pretty apparent. tds.us.henkel.com/NA/UT/HNAUTTDS.nsf/web/382795AAF2B4355B8525760E004BEA0A/$File/263%20NEW09-EN.pdf. If you look at the breakaway torque values for a M10 bolt and nut the value is 33 N-m which is not excessively high but pretty high. However, if you look at the M6 bolt (approximately 1/4" - slightly less) the value is only 5 N-m. which is quite low. My explanation for this is simple: SURFACE AREA. The surface area of the smaller bolt can only hold so much Loctite. With the bigger bolts there is the pi r squared surface area equation that greatly increases the Loctite contact area. You can see the interesting relationship between bolt size and Loctite strength on the TDS. The bolts that hold on the 3800 upper intake are thinner than 6mm. That's why I don't believe I've had any issues with using red Loctite (in my case 272).

[@rheidtech]

Btw. My mother hates that "throttle activity" stuff. Lol.

[@SchrodingersBox]

That sounds really.... awkward

[@pinkhead6857890]

Changed the intake manifold gasket and knock sensors on this very same year truck and disconnecting the battery and all these sensors tripped the security system. After I ovverrode the security system (left the key on for 10 minutes) the truck started but now sounds HORRIBLE. Its now knocking and pinging terribly and barely makes enough power to in ahead in gear. The guy im doing the work for is now accusing me of dropping a bolt into one of the cylinders. Im calling bullshit because the truck sounds perfectly normal when just cranking with the coils disconnected and even if I absolutely destroyed one of the cylinders the remaining 7 should still make enough power for the thing to drive out of my garage. I also made sure to shove rags down all the intake runners before cleaning off the gasket surfaces. My guess is that the P0300 code being displayed on my basic scanner is the result of the crank position sensor loosing its base settings after all these sensors getting plugged and unplugged when pulling the manifold and that it now needs a Crankshaft Variation Relearn to run correctly again. Im terrified of doing any such diagnostic work like that or a compression test that requires cranking the engine due to the dire possibility that there actually might be forgine materials inside a cylinder. Are there any GM guys here familiar with this phenominon?

[@SchrodingersBox]

Why did you change the knock sensors and intake gasket?? what was your original data indicating you needed to do that? That is exactly where you must start to solve this since it is your established baseline. what was that data indicating this would be the fix?

[@pinkhead6857890]

Because the customer had already purchased the parts and he insisted that they were the cause of the P0300 code that the truck had when he drove it over. He was at least right about the knock sensors being bad because there were sitting in standing water and corroded completely brown with rust when I pulled them, the truck ran perfectly fine though when he drove it into the garage bay. According to him it ran rough when the engine was cold, but was still at least drive able unlike now. I should have just waited to let the engine cool down to recreate the symptoms before I started wrenching on the thing, but at the time I just wanted to change the parts he asked me to change--no more no less-- collect my 80 bucks and move on to more important work. Right now my plan for tomorrow morning is to look inside each cylinder with a bore light, run a compression test just to provide definitive evidence that the issue is not mechanical, let the engine knock and ping its way up to operating temperature and then scan the codes a second time to see if I get anything more than that persistent P0300.

[@SchrodingersBox]

So your preliminary diagnostic dataset is “customer said he needed them”?? I mean- obviously you validated this with independent testing or something. You mean you just said “OK” and replaced the parts for a major job without any validation???

[@pinkhead6857890]

Pretty much, I just did what I was told and went full parts changer on that one. I am the 98%, fight me. I wrongly assumed that my boss, the guy who took the truck in and first looked at it, had done at least that much when he pulled me from another job telling me to go change the intake gasket and knock sensors on this truck that just appeared out of nowhere. All I did was note the P0300 code, looked up the torque specs and wrongly assuming that replacing good parts wouldnt make the vehicle run any worse than it already was, now now theres a finger pointing game going on at work. At this point I guess i should just prove that there's no FM in the cylinders to cover my own ass and tell Eric to replace me if he expects me to do technician work for grease monkey pay.

[@SchrodingersBox]

well the problem is you have no baseline data whatsoever. So what data do you have now? What is the LT and STFT at idle vs load and what is the static vs loaded rail pressure? what is your MAF voltage on a throttle position curve?

[@carnivorebear6582]

I think that technician is diffective

[@rheidtech]

Snowin like a BITCH! lol. Awesome vid. A+

[@SchrodingersBox]

Hahaha I was really pissed because my trans am was sitting outside in that snow the whole day while I filmed and fixed this car. It had almost a foot of snow on it by the time I was done and I could barely drive it through the snow back into the garage!!

[@rheidtech]

Holy spotted dick batman!

[@PhattyMo]

YES! Always upgrade to metal intake gaskets. Once again,Plastic = Giant FAIL.

[@SchrodingersBox]

See my comment above- the plastic gaskets are not the reason for the failure- it is the fact that the steel gaskets have much, much thicker sealing material that makes it a better choice. The plastic manifold is actually the problem, not the plastic gaskets.

[@PhattyMo]

On my Pontiac GTP the lower manifold is aluminum (with the blower on top) the original plastic gaskets were falling apart. On the N/A version of the 3800,the intake is plastic,with coolant and even hot EGR gasses flowing through it. *headsmack* Those are notorious for failures,along with the gaskets.

[@satamanschmidt3428]

PhattyMo Correct, Dorman and better yet ATP make a replacement upper intake manifold that includes a SMALLER stove pipe which replaces the factory one. This keeps the gases far enough away from the plastic to prevent its melting. Some replacement upper intake kits also come with an aluminum tube in the EGR passage that avoids this problem as well. When reattaching the UPPER intake I use 1/4" washers under the bolt heads to distribute the bolt loading on the plastic of the manifold. I feel this is mandatory since at 10N-m (89 inch pounds for you metric haters) the heads of these bolts can begin to sink into the plastic.

[@megans.427]

No transmission codes just an engine code 300.

[@SchrodingersBox]

Megan S. Yes I have seen this. I dropped the transmission pan and tested the resistance across the terminals on the shift solenoids and found one to be open. Replacement of the 2-3 shift solenoid fixed the problem in this case.

[@richardfitzwell727]

My mechanic is very skilled. However he's failed to get to the problem. Even with the scope a snap on modis ultra. I'm not saying the scope was not detecting the problem but the operator was not telling the scope what to look for. Needless to say my problem is not fixed. A year and half know.

[@SchrodingersBox]

So what is the problem and what data was collected?

[@juanayala9093]

sorry on a code p0410

[@juanayala9093]

anybody please help

[@SchrodingersBox]

Just do the basic diagnostics and determine if that is the cause of the issue or not.

[@blackiechong4344]

This info means nothing to the DYI.

[@SchrodingersBox]

I have to disagree seeing as how *I AM A DIY* The problem isn't being a DIY or not- the problem is recognizing value in understanding which 98% of DIY's do not.

[@russelldilworth1784]

I have to laugh when I read some comments here..I think a lot of people after watching this video. .think this is exactly the same problem they're having! !!!..Then throw parts at it expecting to fix it! !!.. cos I know MATT hates that approach. .. As Matt clearly shows. .diagnosis thru a process of elimintion is always the best way! !. and of course double checking the fix for the immediate CAHANGE!!!..BRILL VIDEO'S MATT... New subscriber!!!

[@SchrodingersBox]

If you wantr to see comments to laugh at- check just about ANY other channel and watch hundreds of people try to fix this with fuel injector cleaner!!!