Misfire on 8 cylinders

[Redd]

So I was fixing the intake plenum whistle yesterday. Took the intake apart, fixed the leak, put it all back together. Whistle sorted.

Today I noticed the car misfiring. A little bit at first, like small hiccups. Then it got worse and turned into a full-on CEL and limp mode. Misfire on all 8 cylinders. Happens at low throttle openings, or during initial throttle opening during acceleration. When already accelerating or medium to wide open throttle no issues. Once it goes into limp mode, restarting the car clears the CEL, and it drives normally until it misfires again and limp mode.

Took the car to the mech and amongst the misfires the mech saw a "DME: Info: Tank empty on fault entry" code. They thought fueling was the problem, and since the fuel pump was original and 10 yrs old, they thought it needed a new pump. Installed the new pump, same problem. Misfire on all 8 cylinders.

Any ideas what might be causing the misfires? Idle Control Valve, ICV hose, plugs, fuel breather valve, and air pump suction hose with sensor were all replaced 6k kms ago, so they are practically brand new. Could it be MAP sensor (that one is original and 10 yrs old). Or something intake related cos I was fiddling with it yesterday? Car is a 2009 E92 M3.

Please help. Thanks.

[nissanite]

Originally Posted by Redd

So I was fixing the intake plenum whistle yesterday. Took the intake apart, fixed the leak, put it all back together. Whistle sorted.

Today I noticed the car misfiring. A little bit at first, like small hiccups. Then it got worse and turned into a full-on CEL and limp mode. Misfire on all 8 cylinders. Happens at low throttle openings, or during initial throttle opening during acceleration. When already accelerating or medium to wide open throttle no issues. Once it goes into limp mode, restarting the car clears the CEL, and it drives normally until it misfires again and limp mode.

Took the car to the mech and amongst the misfires the mech saw a "DME: Info: Tank empty on fault entry" code. They thought fueling was the problem, and since the fuel pump was original and 10 yrs old, they thought it needed a new pump. Installed the new pump, same problem. Misfire on all 8 cylinders.

Any ideas what might be causing the misfires? Idle Control Valve, ICV hose, plugs, fuel breather valve, and air pump suction hose with sensor were all replaced 6k kms ago, so they are practically brand new. Could it be MAP sensor (that one is original and 10 yrs old). Or something intake related cos I was fiddling with it yesterday? Car is a 2009 E92 M3.

Please help. Thanks.

Redo everything you did yesterday. Retrace your steps and look at all connections and wiring.

Could be a coincidence but I would start there.

[HFG]

Did you sort out the problem ? I have the same exact scenario :/

[Redd]

Yes all sorted. Somehow the air tube going into the ICV was getting stuck intermittently. When this happens, afr goes super rich and the car misfires and throws a code. Dismantling and re assembling everything seems to have fixed it.

After that was taken care of, I still felt the car hiccup/shudder intermittently but no misfire codes. I suspected it was the O2 sensors (still on the original units). Changing those out fixed the issue. Car runs smooth as a baby's backside now.

[HFG]

Originally Posted by Redd

Yes all sorted. Somehow the air tube going into the ICV was getting stuck intermittently. When this happens, afr goes super rich and the car misfires and throws a code. Dismantling and re assembling everything seems to have fixed it.

After that was taken care of, I still felt the car hiccup/shudder intermittently but no misfire codes. I suspected it was the O2 sensors (still on the original units). Changing those out fixed the issue. Car runs smooth as a baby's backside now.

Glad to hear, for me it was an incompatible set of sparks plugs by the previous owner! Changed it and all codes are gone for a day and now facing

Present/DME:Electronics box fan, activation
Not present/DME:Vacuum sensor, brake booster, plausibility

I always wonder what does present & not present mean when scanning codes? does it differentiate between stored and active codes?

[bvrider1]

Always good to see members return back and post up a solution instead of asking and leaving. Thanks guys!!