P0300 - Gone?

[StlRomAniaN]

Hey all,

I know that there have been multiple threads on the P0300 code, but I wanted to create a new one that is specific to my situation. I hope you guys don't mind.

Anyways, I was in Chicago on 10/2 and headed over to a friend's place for lunch after church. It was the usual stop and go traffic. About a half a mile out, my engine started hesitating and shaking, almost like one of the engine mounts went out. Obviously, it was misfiring. Flashing CEL.

I limped to his house and plugged up my scanner to it. I was pulling a P0307 (7th cylinder -driver side and closest to the firewall) and P0300. I could basically smell the unburned fuel that was being dumped into the exhaust. I pulled the plugs and 5, 7, and 8 were wet, with 7 being the worst, which makes sense seeing that I pulled a P0307. The gaps weren't too great either. Nonetheless, I changed all the spark plugs on the spot.

At this point, I thought about my catalytic converters due to all the fuel being dumped in at such a high temp. I jacked the car up and unbolted my aftermarket exhaust. Sure enough, the cats were fried. I pulled off the connecting pipe and gutted the cats. Much harder than it looks by the way.

I then went on to check the coil packs; troubleshooting mode. I turned the car on and proceeded to unplug each coil pack plug one at a time to hear an RPM drop. All cylinders turned out to be fine, except 5, 7, 8. I replaced them just because. I'll check the old ones with an ohmmeter and potentially put those back on so that I can return the new ones.

I just went back up to Chicago this past weekend to trailer it down and I turned the car on. At the beginning, it shook and pulled the P0300 code again, but as it got warmer, the code went away and the car idled perfectly. Regardless, I continued to load it onto the trailer for the trip back to St. Louis. The car started and idled perfectly when I offloaded it in St. Louis too.

This tells me that nothing is wrong internally (lifters, rockers, springs, etc.), I believe. What could it be then? Something is thinking that I have too much air in my system, which is then telling my engine to dump more fuel into the cylinders, or I actually am pulling too much air into my system via a vacuum leak.

MAF sensor? 02 sensor? Stuck fuel injector that became unstuck? Air intake manifold leak? That would make sense since my problem cylinders are all adjacent to each other. That's also where the loudest ticking is taking place.

I'm just looking for opinions on where I should start and what you think it might be. I know the code is gone, but I'd like to resolve the issue instead of relying on this "temporary bandaid."

Thanks!

[StlRomAniaN]

2010 Camaro SS
1 7/8" ARH Headers w/ 3" all the way back into SLP Powerflo mufflers
ADM Race Intake w/ scoop
ECM/TCM tune

Those are all of my modifications that would directly affect air flow.

[JD_Alaska]

I'd say log LTFT,STFT,MAP,MAF and O2. Need more information to help see what's going on

[StlRomAniaN]

Cool! I'll log this when I'm home tonight. Hopefully I can do this with my Actron CP9580A.

Are there any numbers/patterns I should be looking at when checking the LTFT, STFT, MAP, MAF & O2?

[KaBoom1701]

Originally Posted by JD_Alaska

I'd say log LTFT,STFT,MAP,MAF and O2. Need more information to help see what's going on

Agreed. Since you have a tune data log the car and work with your tuner to help diagnose the problem.

[StlRomAniaN]

Originally Posted by KaBoom1701

Agreed. Since you have a tune data log the car and work with your tuner to help diagnose the problem.

He's now in Texas so it's a bit difficult. It's been tuned for 5 years now with no problem. I'll report back the above parameters when I'm home later tonight.

[StlRomAniaN]

Originally Posted by JD_Alaska

I'd say log LTFT,STFT,MAP,MAF and O2. Need more information to help see what's going on

Does the engine need to be fully up to temp for these tests? Only idle, or cruise and WOT as well? Thanks.

[ChibiBlackSheep]

Originally Posted by StlRomAniaN

Does the engine need to be fully up to temp for these tests? Only idle, or cruise and WOT as well? Thanks.

Yes the engine needs to be fully warmed up, your PCM dumps a lot of fuel at the car until the oxygen sensors get up to temp.

I would check IDLE and CRUISE and not go WOT until you figure out the issue. WOT locks in the current AFR and fueling, so if you are leaning out the engine without realizing it, you can get some bad detonation at WOT. Or if you are running really rich, you will just pour fuel at WOT.

Since this is only happening on one side of the engine, I would check that side's pre-cat oxygen sensor. That should be the one that reports the most for those banks to tell the car how much fuel to throw.

Also check all of the header sections on that side of the engine. Maybe you have a cracked coupler, or maybe one of the collectors has a hairline crack it in and it is letting out before the oxygen sensor gets the read.

Other than that, perhaps take this car to a tuner and get it checked out. The person that originally tuned your car could have just added timing until they made the power they wanted, then dumped fuel at it to combat knock.

Also, how clean is your engine? Sometimes you can get a ton of buildup inside the engine that kills the efficiency. Can you pull a valve cover, or the UIM and take a look at how caked everything is, or if it's clean?

[CamaroFred]

Did you buy fuel in Chicago?

[StlRomAniaN]

Originally Posted by ChibiBlackSheep

Yes the engine needs to be fully warmed up, your PCM dumps a lot of fuel at the car until the oxygen sensors get up to temp.

I would check IDLE and CRUISE and not go WOT until you figure out the issue. WOT locks in the current AFR and fueling, so if you are leaning out the engine without realizing it, you can get some bad detonation at WOT. Or if you are running really rich, you will just pour fuel at WOT.

Since this is only happening on one side of the engine, I would check that side's pre-cat oxygen sensor. That should be the one that reports the most for those banks to tell the car how much fuel to throw.

Also check all of the header sections on that side of the engine. Maybe you have a cracked coupler, or maybe one of the collectors has a hairline crack it in and it is letting out before the oxygen sensor gets the read.

Other than that, perhaps take this car to a tuner and get it checked out. The person that originally tuned your car could have just added timing until they made the power they wanted, then dumped fuel at it to combat knock.

Also, how clean is your engine? Sometimes you can get a ton of buildup inside the engine that kills the efficiency. Can you pull a valve cover, or the UIM and take a look at how caked everything is, or if it's clean?

Thank you. I will look into all of this. For tonight, I just checked idle.

[StlRomAniaN]

Originally Posted by CamaroFred

Did you buy fuel in Chicago?

I bought gas from Shell in Bloomington, IL. 93 octane. I avoid filling up in Chicago due to the high prices.

[StlRomAniaN]

Here are my OBDII results at idle with engine fully warm:

Barometric Pressure: 29.5 "Hg
MAF: 0.67 LB/M
MAP: 8.3 "Hg
02 (Bank 1): Min: 0.06; Max: 0.865
02 (Bank 2): Min: 0.06; Max: 0.830
Fuel Pressure: 58 PSI
LTFT (Bank 1): -1.6
LTFT (Bank 2): -2.3
STFT (Bank 1): Min: -6.3 w/ one -7.8 spike; Max: 5.5
STFT (Bank 2): Min: -6.3; Max: 5.5

[StlRomAniaN]

Oh, and no more CEL. No misfiring. Nothing.

I'm thinking that the cats that I punched out last weekend clogged the system up a bit basically trapping the air in the exhaust near the first pair of 02 sensors. The 02 sensors sensed all of the air and considered my engine as running lean. It then dumped a bunch of fuel into my engine.

Now that I've let it run long enough, it seems as though my engine is no longer "flooded" with fuel. It sounds healthy minus the typical ticking sound from these LS engines.

[ChibiBlackSheep]

Your LTFTs and STFTs are all within their acceptable ranges, even running a tad on the rich side (which is better than the lean side)

Hopefully your data during cruising stays as clean as that.

I'm still concerned about clogged cats, how long have those cats been on the car? They shouldn't fail that quickly.