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Old 02-07-2012, 09:17 PM
Join Date: Aug 2009
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Lots of OBD-II trouble codes...

Hi everyone.

As the title says I have a misfire problem, I have taken it to my local mechanic and with me watching, he hooked up his huge diagnostic system and watched the misfires in real time. Also, we checked several potential easy fixes, such as a coil pack, I had another coil pack, hooked it up, still misfiring on cylinder 2 (Kind of confirms its not the coil pack). Then we changed the boots on the coil pack swapped x for 2, checked again, misfire on cylinder 2 remains (confirms boot is good). Then we swapped out the fuel injector from x to 2 then did ran diagnostic again, misfire remains on 2. We did the same with the spark plugs too.

With the above information, the mechanic has pretty much confirmed its not an electrical problem. He is convinced I have sludge in the motor and it happens to be worse on cylinder 2, This makes perfect sense to me as it does not really misfire when driving, mainly when idling. Now, Since then, I have had such bad luck, I recently had the engine replaced, (this started happening then), this moron mechanic (not my local guy) connected the flywheel to the torque converter with an incorrect bolt, which caused the transmission to crack then leak in the flywheel area. (Right after I did a transmission fluid change too, I'M MAD!!), anyhow, I had a competent mechanic replace the transmission too, he discovered that issue caused by the previous mechanic and got me set up right, this is when he ran the diagnostic again, I still had the misfire a month later, but he said it had got better. Instead of 12 misfires for each cycle (100), I was getting much less, probably because I replaced one of my quarts of oil with marvel mystery oil.

I also get bad oxygen sensor error codes, my mechanic says all my check engine lights are related to this misfire, the oxygen sensors are basically, so covered in carbon due to the misfire that they cannot work right (I see this carbon on the end of the exhaust pipe too, it also smells rich sometimes too)

I believe that cleaning the sludge then cleaning the oxygen sensors should get my check engine light off.

Hopefully, the above information will help you guys answer this question..

Do you think continuing to clean the engine slowly would fix this issue, eventually?

Thanks in advanced!

Last edited by johnccc; 02-18-2012 at 10:16 PM. Reason: Renamed title to be more relative to the topic
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Old 02-08-2012, 04:36 PM
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Old 02-08-2012, 04:47 PM
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try seafoam
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Old 02-08-2012, 05:43 PM
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most likely carbon build up on your valves and causing valves no to seat properly had simular problem with a caddy and only misfired at idle and i ended up being carbon on valves and ended up ripping heads off and getting head cleaned by a machine shop, one thing you can do is take off your intake manifold make sure your valves are closed in cylinder 2 and pour some of gm's cleens and let it sit for a couple of hours to help break the carbon up< only if thats what the issue is, good luck
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Old 02-08-2012, 06:24 PM
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I added seafoam about 500 miles before I changed the oil, then I added the mystery oil to the crank case with my oil, also used a thinner grade of oil hoping to help it pick up some sludge, however, I'm monitoring my oil levels often. (seems to be working slowly)

I have asked my mechanic to rebuild the entire motor, I really am picky about these little issues and am willing to spend the $400 it would be to get rid of this damn issue, but he said he does not want to do it...

Purely guessing, how long do you think it would take to get rid of the misfiring doing what I'm doing now?

As for the carbon build up, I not a mechanic, but I know how a car works, but not really how to get around them, I have the Haynes manual, which section of the manual would I be looking at for removing the intake manifold? The closest successful repair to that I have done is removing throttle body for cleaning and replacing the head valve cover gasket seal (When I looked at the cover it had one dirty large patch of sludge, which I cleaned).

Thanks all
Old 02-08-2012, 07:13 PM
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Was the code 0300 or 0302? Are you burning e85?
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Last edited by Coby7; 02-08-2012 at 07:15 PM.
Old 02-08-2012, 07:41 PM
Join Date: Aug 2009
Posts: 924
I dont exactly remember the code, pretty sure it was 302 though, it did clearly say misfire on cylinder 2 however.

Burning E85, possibly, I gas up at shell and no other, shell gas "MAY" contain up to 10% ethanol, thats what it says on their pumps. However, I never had this issue in the previous engine, just in the replacement one.

To be honest, its a little more complicated. Here it goes.....

In the original engine I was not getting this cylinder 2 error, however, after a coil pack fail (flashing check engine light) I believe the oxy sensors got degraded, they were never cleaned after replacing the coil pack, at this point I was not getting misfire, but did have check engine light for the oxy sensors

That engine is no longer in the car, as a mechanic... (I explained above)...

Now, I have a rich burning smell in this replacement engine, and getting this misfiring issue, I can feel the car, like it wants to turn off, but just a little, then continues like that, turning on the AC does help reduce the misfire feeling, but it still happens
which is shown on the diagnostic machine and also you can feel the engine misfiring, when idle.

I truly believe the engine is dirty and needs a good clean, it was from a 2004 Saturn, same engine, just much older.

I have decided to invest in a ELM 327 cable and got some software on my laptop, I will be diagnosing myself from now on.

The mechanic said may cars do this when not maintained well, "its not an issue". I'm picky, its an issue for me. I want clean.....

From the info (tests) in the 1st post, can I conclude that it must be the engine itself?
Old 02-08-2012, 09:33 PM
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pretty much, look for intake swap how to with pics it will show how to remove
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Old 02-10-2012, 10:39 PM
Join Date: Aug 2009
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I will be replacing the rack and pinion Tuesday, I will look at it then, I will update the findings here then.

Thanks for the information...
Old 02-17-2012, 12:18 PM
Join Date: Aug 2009
Posts: 924
Okay all, I got some new information.

I just received my ELM 327 Car to USB adapter, I have their official app on my laptop.

I can read all trouble codes and clear them, which I just did.

So, I instantly get "Pending codes" (codes that exist, but to not eliminate the check engine light, yet).

1st one, is "System too lean" P0171.

I can get pretty much any information from the cars computer with this, so hopefully we can narrow down some issues.

Also, the scantool app has an oxygen sensor test, bank one completes bank 2 fails, but...

If I rev the engine for a few seconds, then hold it during the test, both tests complete.

I am not getting the misfire code, however, I will have to leave it for a little bit longer and see what comes up.
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