[Godzilx]

During autocross this weekend I had my car sitting for around 3 hours after my first run. Upon starting it, the car's idle started misfiring like crazy. I had always had an unstable idle but this was almost popping and misfiring for the entire coldstart phase. This keeps happening whenever the car sits for an extended period of time and enters the 'cold start phase' where it takes around a minute to get to 600rpm.

The next day the misfire codes began happening on cylinders 4-6 all at once.
I took out the plugs and coils around two hours after having driven the car (probably should've waited longer) and the only plug that smelled like gasoline was cyl 3. I have flipped the order of all the plugs and coils and am going to see if it persists tomorrow. Once the car is warm it drives perfectly, but cold starts are violent and a 'service engine soon' light pops up. No fuel mixture codes or mosfet codes, just the misfires

I have a datalog of the bad cold start

https://datazap.me/u/godzilx/coldsta...og=0&data=3-22

Bank 2 AFR seems strange but I'm not familiar with reading fuel related information.

I would really appreciate if anyone could give pointers before I drop $1600 on new injectors- crazy how much the price has gone up. The reason I'm skeptical about it being injectors is suddenly getting all bank 2 misfires at once. Don't think it would be O2 sensor as from my understanding they aren't active in the cold start phase.

[bimmerguy1210]

Likely the mosfets gone bad in your msd80 ecu. When they go, they'll trigger misfires in all cylinders for each bank.

[Dave92N54]

Originally Posted by bimmerguy1210

Likely the mosfets gone bad in your msd80 ecu. When they go, they'll trigger misfires in all cylinders for each bank.

They wouldn't go away when warm. My guess is 02, OP does it start IMMEDIATELY after starting the car, or maybe 20s after? The 02s heat up pretty quickly, they get used almost immediately. Though with your symptoms, i'm not sure. I myself have fixed cold start issues with 02s, along with others. In my case it was barely noticeable, passengers would say they couldn't even tell, and it never threw a code.

I've had a bad injector and while it did what you're describing, it never threw a code and it was pretty obvious when I pulled the plug, tip was completely black even after a short period.

[Godzilx]

This morning I got cylinders 1,5, and 6 misfires. I have MSD81 as well. Not sure what it is then.

[Godzilx]

It's quite quick for the misfires to start but there's a few seconds while it revs up on the start where its not misfiring. Today I got a misfire on cylinder 1,5, and 6. Would that rule out O2s?

[Saif2018]

Have you ruled out plugs and coils first?

[Godzilx]

Originally Posted by Saif2018

Have you ruled out plugs and coils first?

I flipped the order of the the plugs and coils; cyl 1 and 6 swapped, same with cyl 2 and 5, 3 and 4. Misfires still occurred just cyl 1 misfired instead of 4.

[Saif2018]

Originally Posted by Godzilx

I flipped the order of the the plugs and coils; cyl 1 and 6 swapped, same with cyl 2 and 5, 3 and 4. Misfires still occurred just cyl 1 misfired instead of 4.

Injectors? Have you tried swapping them as well?

Just tp rule them out, but Dave is probably right, looks like O2 related

[Godzilx]

Originally Posted by Saif2018

Injectors? Have you tried swapping them as well?

Just tp rule them out, but Dave is probably right, looks like O2 related

So I tried logging precat o2 voltage with protools and both banks are a steady 1.9-2.1V on coldstart, while the car is misfiring. Back to 4,5,6 misfiring. No fuel codes just misfire codes. Car starts misfiring within 5 seconds of car starting

[Saif2018]

Originally Posted by Godzilx

So I tried logging precat o2 voltage with protools and both banks are a steady 1.9-2.1V on coldstart, while the car is misfiring. Back to 4,5,6 misfiring. No fuel codes just misfire codes. Car starts misfiring within 5 seconds of car starting

Did you inspect/swap the injectors to rule them out?

Have you checked post cat O2 sensors as well?

I'm not sure if voltage checks are enough tell you that O2 sensors are working properly.

[iqraceworks]

First thing to do it check for leaky injectors.......I bet you will find some.

It's easy to do, only take a few minutes to pull the spark plugs out after the car has sat for a few hours and see if they are wet or smell like fuel.

I had a cold start "bobble" that went away after the car ran for a minute......yep, leaky injector. The new injector cleared the problem right up.

[Godzilx]

Originally Posted by Saif2018

Did you inspect/swap the injectors to rule them out?

Have you checked post cat O2 sensors as well?

I'm not sure if voltage checks are enough tell you that O2 sensors are working properly.

Have new injectors arriving tomorrow. Just going to throw them on now since they're index 12 and through fcp. My rear o2 sensor is new on bank 2 as well

[iqraceworks]

Originally Posted by Godzilx

Have new injectors arriving tomorrow. Just going to throw them on now since they're index 12 and through fcp. My rear o2 sensor is new on bank 2 as well

So did you check your injectors and find a bad one(s)??.....or are you just replacing all of them for the hell of it and hoping that fixes your issue??

[Saif2018]

Originally Posted by Godzilx

Have new injectors arriving tomorrow. Just going to throw them on now since they're index 12 and through fcp. My rear o2 sensor is new on bank 2 as well

Since you've ordered them, at least check your plugs for any smell of fuel/oil.

Personally don't think it's a good idea to throw money at a problem without ruling out as many things as possible, but can't complain with FCP warranty policy.

[stewbets]

Originally Posted by Godzilx

Have new injectors arriving tomorrow. Just going to throw them on now since they're index 12 and through fcp. My rear o2 sensor is new on bank 2 as well

If I were to guess, I'd say injectors aren't going to fix your problem. I've not heard of injector issues going away once the engine warms up. Also, you'd likely be getting some long cranks if the injectors were causing your cold start misfires. The problem is that I don't know what your issue is. It almost sounds like a bad ground that is temperature related. I'd also try re-flashing your tune just because it's easy enough to do and this is a wonky issue.

[Godzilx]

Originally Posted by iqraceworks

So did you check your injectors and find a bad one(s)??.....or are you just replacing all of them for the hell of it and hoping that fixes your issue??

Just replacing them all as I'll need to eventually. I've ruled out plugs and coils, O2 sensor seems fine. For the gas smell test it's very faint to the point where I may just be imagining it. The tip of the coil on cylinder 3 smelled strongly of gas however. Checked the injector line by it and no leak so not too sure how that happened

[iqraceworks]

Do you have any oil around your coils? Is your valve cover in good shape?

[Godzilx]

Originally Posted by iqraceworks

Do you have any oil around your coils? Is your valve cover in good shape?

Today I started the car with the new injectors and I'd say it's significantly better maybe 75% better, but some hiccups are still there. My oil cap is leaking a good amount of oil. Valve cover gasket is around 10k miles old and doesn't appear to be leaking.

[stewbets]

This doesn't make any sense to me. You went from no codes, to persistent, repeatable misfire codes on 3 cylinders, and new injectors fixed that? Before I upgraded to index 12 injectors, I played around with a bunch of used injectors, many of which were bad, but I never had misfire codes from them at idle. They only caused long cranks and rough idling for the first few seconds while the excess gas burned off. I guess I'm not understanding how you had a whole bank of injectors go bad at the same time in such a way that it throws codes but doesn't render the car undriveable at temperature.

[stewbets]

Don't get me wrong, I'm glad you're not experiencing misfires now. I'm just thinking out loud about what caused the sudden and specific type of injector failure.

[Godzilx]

Originally Posted by stewbets

Don't get me wrong, I'm glad you're not experiencing misfires now. I'm just thinking out loud about what caused the sudden and specific type of injector failure.

I'm just as confused. Also misfire codes were becoming completely random. Looking at my dme history from when this started: I got 4,5,6 three times. But I've also gotten: 1,2,3,4 and 1,5,6 twice , also 1,2,6. The problem isn't completely fixed only better after new injectors. I will see how the car continues to act in the next few days.

But overall, first I swapped around coils and plugs when getting misfires on 4,5,6. I basically swapped banks 1&2 coils and plugs and still got the 4,5,6 so I ruled out plugs and coils. Then each morning different cylinders would have misfires. O2 sensors don't make sense to me as the entirety of bank 2 wasn't always misfiring. Also the voltages seemed fine. I feel if it was o2s I'd have consistent bank 2 misfires.

The only other conspiracy I have is that for the past 2 years I've gone to one shell station. A week ago their system was down so I went to BP and filled up on 93 there. I very highly doubt this would have caused this but three days after the car started acting up.

What I have left to try is reflashing my tune and see if my goes completely away. This has been a goose chase with no definitive answers.

[Godzilx]

Update, turns out my precat bank 2 sensor has gone bad. I now have codes 2CA7 and 2CAB when the car is running.

Since replacing the injectors I've still not gotten any misfire codes whatsoever. Still hiccups on idle but cars been driving much better. Going to replace the O2 and the idle should be perfect.