[||||||||||]

Okay, this might be long, so bear with me.

Backstory: Back in November just before putting the M3 in winter storage I was cruising along in 1st or 2nd gear at low speeds (coming up to a stop light) and my CEL light popped on, got Increased Emissions, reduced power warnings and hit limp mode. I drove a mile, stopped, turn the car off, restarted it, and the limp mode was gone, but upon scanning for codes, I got cyl 5, 6, 7 and 8 misfires. I cleared the codes, drove the next day, and the limp mode came back a couple times. All my research lead me to believe it was the bank 2 throttle actuator, and with the car about to go away for the winter, I decided to do it as a winter project and deal with it later. So I parked the car.

Current situation: A few weeks ago I replaced my bank 2 TA and took the car out of the garage for the first drive in 4 months. I figured all was well, but after driving about 30 miles, I got limp mode again. Scanned my codes, and got the same codes. Drove another 15 miles, and hit limp mode again. Obviously the new TA didn't fix the issue, so I took it out, popped the old one back in, and while I was in there, I switched my left side and right side ignition coils just so I could rule them out. Drove 10 miles, and hit limp mode again. Scanned the codes (this time with engine running, and limp mode activated) and got cyl 5-8 misfires, PLUS a P0223 for my throttle position sensor. I turned the car off, and restarted it, and scanned my codes again, and the P0223 was mysteriously gone (not even stored) as though it never happened. I drove the car today and throughout the day I hit limp mode twice. Scanned the car when I got home, and this time I had cyl 1, 2, 3, 5, 6, 7 and 8 misfires (all cyl but # 4).

So I'm pretty frustrated and confused at this point. Here are the specifics of my issue:

1. Car only seems to misfire at low speed, and low RPMs in low gear (i.e. when cruising up to a stop light or stop sign and keeping steady throttle at around 1500-2000 rpms). It has only misfired one time in other conditions, and that was the other day cruising down the Autobahn around 55mph.

2. I always get cyl 5-8 misfires consistently, plus the multiple cyl misfire code, except today, when I got all cyl but # 4 for the first time ever.

3. I got a code for my IAT sensor bank 1, Coolant Temp sensor and Throttle Position Sensor Bank 1 a couple weeks ago, plus my P0223 for TPS sensor yesterday when the car happened to be misfiring and in limp mode. These were a one time thing, except for the TPS sensor which has happened twice.

4. When the car hits limp mode, at idle it will sound noticeably rougher, idle at 1000 RPMs and shake/shudder. Otherwise it seems to drive okay aside from having a reduced rev limit of 4500-6000 rpms

5. Turning off the car and restarting it ALWAYS clears limp mode, seems to fix the misfire and makes the car run perfectly normal as though nothing happened (though the codes are obviously stored in the computer).

6. Not sure if it's related, but lately a few times at idle (mostly when starting the car) it seems like the car has been struggling to maintain an idle point, and will sort of "bounce" around 500 rpms. It is fairly subtle, and you might not notice it unless you are looking at the tach. I have also had an issue in the past where the car has failed to start (happened twice, though not for a long time). The car just kept turning over, but wouldn't fire up, until I hit the starter button and then pressed it again to turn the car over, at which time it started okay.

What does this sound like, or where can I start? Anything I can test to rule it out? Hopefully someone can help. I asked on M3Post and am not really getting anywhere.

[SPEEDBUMP]

I have the exact issue, literally all of the same symptoms and I was not convinced that the TA's were the source of the problem. Your post confirms my suspicions about this being linked to a different problem. I swapped the oxygen sensors from left to right and that changed nothing - just like you swapping the coils from left to right.

I currently show bank 2 misfires only (cylinders 5,6,7,8 & multiple misfire code). My plan is to replace the spark plugs as well as all 4 fuel injectors on bank 2.

My theory is that one of the injectors is stuck open flooding the cylinder at low RPM. I'll let you know what happens when I get these changed within the next week.

Let me know if you have had any progress with your repair.

Cheers,
Andy

[SPEEDBUMP]

Problem solved - I replaced the fuel injectors on bank number 2 and the issue has not returned. If you have not already found a solution I suggest you try this.

Fuel injectors are not cheap so you may want to do as I did and find a used set from a wrecked vehicle. This was a lot less expensive than buying new.

For good measure I chose to replace the OEM spark plugs at the same time. The original plugs had 55,000 kms on them.

All good for now

Good luck,
Andy

[SPEEDBUMP]

My problem has returned so the saga continues....

It's going to the dealer on Friday as the car has become a paperweight at this point. I will post regarding the final solution once the problem has been corrected.

Andy

[Psiddy81]

Have you checked to ensure you don't have any exhaust leaks, they can cause misfire fault codes etc.

Worth a thought anyway!

[SPEEDBUMP]

Originally Posted by Psiddy81

Have you checked to ensure you don't have any exhaust leaks, they can cause misfire fault codes etc.

Worth a thought anyway!

Good call. I recently had the car with another mechanic and they found an exhaust leak between the headed and my Akra X-pipe on the same side of the engine as the misfire.

Since the repair the car seems to be running fine so hopefully this is the very last post I have to make regarding this issue!!

Cheers,
Andy

[pbonsalb]

There are also a couple of fuel pressure sensors that have caused issues for some. I am not sure which -- there is a high and a low. I replaced the low on my car but have read of others replacing the high.