Engine Misfire, fluctuating idle, and backfire after test pipes and tune

[Xology]

TIA for comments and help.

So there are a few things I've noticed in the past month or so. They may be unrelated but they've all started around the same time so i wanted to get everyone's opinion.

I have an 2008 E90 M3 with ~53K miles. I recently installed test pipes and got a stage II tune (without cold start delete). I also finally found a gas station that has 93 octane and have been exclusively filling with this (but my tune is set up of 93 octane).

After test pipes and tune, I started to notice a fluctuating idle - almost exclusively on a cold start (see video below). It is usually the worst first thing in the morning, but even after that it is still present - just maybe not as severe.

The other thing I noticed is that I get a lot of popping sounds (I believe its a backfire) when come off the gas on a quick rev (see video below). If I rev up slow and ease off the gas, I generally don't hear this popping sound. Again, this is most pronounced or noticed on a cold start but does occasionally happen at other times. It's not very noticeable in the video due to launch control not allowing me to rev past 3500, but more noticeable in reality when driving.

Finally, I got a check engine soon light and ran diagnostics on it with the cable from tune and got error codes 2B42, 2B43, 2B44, 2B45, 2B46, 2B47, 2B48, and 2B49 = "Misfire impairing exhaust emission" on Cyl 1-8. I also got my oil changed at the dealer and asked them to check codes and they got the same plus a bunch of other (likely irrelevant) codes (see below)



https://drive.google.com/file/d/0ByK...ew?usp=sharing

So what are your guy's thoughts?

1. From what I've read on the forum, others with this problem (uneven idle) it can be from spark plugs (but all 8 cylinders at the same time??) or maybe the idle control valve

2. Could there be issues with the tune? (Fuel management for the backfiring?)

3. Could not having the cold start delete be contributing to this issue

Thanks guys

[Xology]

i don't know why none of my embedded videos aren't showing up.... i'll work on it in bit

[Redd]

Cold start delete should not cause this. I've run my car stock, stage 2 tune with cold start delete, and stage 2 burble tune without cold start delete, and never saw the symptoms you describe above.

Which tune is this? Is it possible they sent you the wrong tune?

[O8E92M3]

I have been having similar symptoms lately, especially the misfire impairing exhaust emissions in all cylinders.
Would love to know tech opinions.

[PeruM3]

I had the same erratic idle and error codes before the tune. Everything was solved once I installed the tune with cold start delete. I know it's not your case but you should try to get the tune with cold start delete and see if it helps.

[O8E92M3]

Just got to see the videos, not the same as what I have.
Especially with the weird idle in the first video

[BPMSport]

Something causing a misfire on all banks would likely be a faulty ICV, tank vent valve, or low pressure fuel sensor. It could also be an o2 or TA, but much less likely.

Are there any other faults other than the 8 misfire faults?

I would recommend flashing to stock and seeing if the problems persist. If they do, then it's likely due to the test pipe installation or something related if these problems didn't occur prior to installation.

[Xology]

thanks for the input. I was planning on starting with some new spark plugs, to see if that made a difference, wanted to replace them anyway. Just ordered the spark plugs earlier today, hopefully ill get a chance to put them in next weekend

Shouldn't be the fuel pressure sensor as I just replaced fuel lines and pressure sensors a few months back.

I like the idea of flashing back to stock to see how that effects the symptoms. Will try that first and see if it makes any difference.

[BPMSport]

Originally Posted by Xology

thanks for the input. I was planning on starting with some new spark plugs, to see if that made a difference, wanted to replace them anyway. Just ordered the spark plugs earlier today, hopefully ill get a chance to put them in next weekend

Shouldn't be the fuel pressure sensor as I just replaced fuel lines and pressure sensors a few months back.

I like the idea of flashing back to stock to see how that effects the symptoms. Will try that first and see if it makes any difference.

Spark plugs are great to change, but I would wait until you resolve this issue before replacing all of the plugs. There is something else causing this issue. If it was a misfire in one or two cylinders then plug replacement would make sense in those cylinders.

[Xology]

OK so after posting, i just cleared the codes just to see if they came back with driving. Took my car to work (5 min drive) and back and the check engine light showed up again on the way back home. When I ran the diagnostics, this time it only had a misfire code on cylinder 3. I wonder if the previous misfire codes accumulated over time...

Yesterday, as suggested, I cleared all codes and flashed back to stock. I took the car out for a nice long drive and some spirited driving. Thankfully no codes - so far... I'm taking her out again to see if any codes come up. The weird idle issue and backfiring is also gone but so far this is just an n=1. lets see what today brings.

Any new thoughts on what might be going on?
Will report back after today's drive

[Xology]

went for nice long drive with a couple of hard pulls. No error codes. The fluctuating idle is gone now but the backfiring/popping is still there (only for the first few min of driving) - don't know if thats just a byproduct of the test pipes?

[BPMSport]

Originally Posted by Xology

OK so after posting, i just cleared the codes just to see if they came back with driving. Took my car to work (5 min drive) and back and the check engine light showed up again on the way back home. When I ran the diagnostics, this time it only had a misfire code on cylinder 3. I wonder if the previous misfire codes accumulated over time...

Yesterday, as suggested, I cleared all codes and flashed back to stock. I took the car out for a nice long drive and some spirited driving. Thankfully no codes - so far... I'm taking her out again to see if any codes come up. The weird idle issue and backfiring is also gone but so far this is just an n=1. lets see what today brings.

Any new thoughts on what might be going on?
Will report back after today's drive

Would replace plug and coil in cyl 3. But wait and see if anything comes back.

[Duralumin]

Ive got the eng malfunction on cyl 5,6,7,8 too. Will start a new thread soon

[BPMSport]

Originally Posted by Duralumin

Ive got the eng malfunction on cyl 5,6,7,8 too. Will start a new thread soon

Probably the throttle actuator for that bank, or o2 sensor.

[Duralumin]

Thanks for the reply mike. I was about to ask you abt the throttle actuator. Is it possible that the TA fails but no TA error code

The error codes are only misfire with cutoff cyl 5,6,7,8. Misfire on several cylinders. Im running catless with software tune

Car is at bmw for three weeks now. They have swapped plugs, coils, injectors from bank 1 to bank 2 but still no luck so far. They dont seem to know what to do

[Black.m3]

Hi, i had the same issue "Misfire impairing exhaust emission" on Cyl 1-8 after 2 months when i replaced my stock exhaust with the IPE F1, no limp mode, no reduce power, but the CEL came just one time, i removed and for the moment i didn't get the CEL again it's been 3 weeks.. did you solve it please ?

PS : i feel like i have less torque with this exhaust

[2011_M3]

Originally Posted by Black.m3

Hi, i had the same issue "Misfire impairing exhaust emission" on Cyl 1-8 after 2 months when i replaced my stock exhaust with the IPE F1, no limp mode, no reduce power, but the CEL came just one time, i removed and for the moment i didn't get the CEL again it's been 3 weeks.. did you solve it please ?

PS : i feel like i have less torque with this exhaust

Did you every find out what caused the problem. My m3 just went into limp mode 2 weeks ago and I scanned it and said misfire cylinder 5 and 6. I changed the spark plugs, coils and o2 sensors on the driver side and still got a engine malfunction light. I'm going to install the other 2 sensors tomorrow to see if that fixes it.

[Black.m3]

Originally Posted by 2011_M3

Did you every find out what caused the problem. My m3 just went into limp mode 2 weeks ago and I scanned it and said misfire cylinder 5 and 6. I changed the spark plugs, coils and o2 sensors on the driver side and still got a engine malfunction light. I'm going to install the other 2 sensors tomorrow to see if that fixes it.

For the moment no, I put back the oem exhaust, i think it’s due sometimes to the bad quality of the gasoline perhaps but i wanted to change my idle control valve + fuel tank breather as i have fluctuating idle at cold only and misfire on all cylinders. The low pressure fuel sensor can also cause this trouble as I have read on some forums. Btw I don’t have a loss of power. What was your codes ?

[Macyvaladeztruspeed]

Originally Posted by Black.m3

For the moment no, I put back the oem exhaust, i think it’s due sometimes to the bad quality of the gasoline perhaps but i wanted to change my idle control valve + fuel tank breather as i have fluctuating idle at cold only and misfire on all cylinders. The low pressure fuel sensor can also cause this trouble as I have read on some forums. Btw I don’t have a loss of power. What was your codes ?

Have you figured it out? Sorry to open a old thread but I’m having these same issues but with a supercharger I’ve changed the fuel vent valve, and 02 sensors and it still happening

[Black.m3]

Originally Posted by Macyvaladeztruspeed

Have you figured it out? Sorry to open a old thread but I'm having these same issues but with a supercharger I've changed the fuel vent valve, and 02 sensors and it still happening

Sorry i saw now your post, i changed 3 days ago, the IDLE control valve, the fuel tank breather, the low pressure fuel sensor and the water temperature sensor. For the moment i have a very minimal fluctuation at cold, almost none, the RPM looks like stable from what i've seen, before to install those items it fluctuated more at cold, so it appears to be resolved and i felt like the car is at his best when i drove it.. But i ll tell you if i have an issue in the coming days, if yes, IMO it might be the ignition coils or the spark plugs together that need to be changed maybe. I ll also check fault codes and drop it here if the CEL appears again.

[Macyvaladeztruspeed]

Originally Posted by Black.m3

Sorry i saw now your post, i changed 3 days ago, the IDLE control valve, the fuel tank breather, the low pressure fuel sensor and the water temperature sensor. For the moment i have a very minimal fluctuation at cold, almost none, the RPM looks like stable from what i've seen, before to install those items it fluctuated more at cold, so it appears to be resolved and i felt like the car is at his best when i drove it.. But i ll tell you if i have an issue in the coming days, if yes, IMO it might be the ignition coils or the spark plugs together that need to be changed maybe. I ll also check fault codes and drop it here if the CEL appears again.

Thanks man, I ended up getting the tune changed and it fixed itself but Is slowly getting a little more weird but nowhere near what it was. Do keep me in the know as I have yet yo change the idle control valve

[Black.m3]

Originally Posted by Macyvaladeztruspeed

Thanks man, I ended up getting the tune changed and it fixed itself but Is slowly getting a little more weird but nowhere near what it was. Do keep me in the know as I have yet yo change the idle control valve

I'll, and if it might help you : 5 Symptoms of a Bad Idle Air Control Valve
1) Intermittent Idle Speed.
2) Check Engine Warning Light.
3) Rough Idling.
4) Engine Stalling.
5) Load Causes Stalling.

Good luck