Hi all,
Been trying to diagnose some rough idle and performance issues over the last few weeks (posted in here a few weeks back already). Think I may have made some progress in diagnosing and want to sense check my thoughts before dropping £££ on new bits.
Car: 2006 E86, manual, black plastic valve cover N52B30 with 163k miles
Symptoms:
- Slightly rough idle. Rpms fluctuate between about 670 and 730, seems the same whether the car is warm or cold. Seems to be a bit worse on a cold day but I could be imagining that. Tangible shake and an intermittent popping sound a bit like a misfire.
- Exhaust smells rich, especially on startup. Long term fuel trims sit at 6% both banks, short term somewhere between 7% and 10% both banks.
- Engine a bit hesitant at low RPMs, makes changing from 1st to 2nd lumpy.
What I have tried thus far:
- Replaced VVT motor gasket. It was leaking oil and I thought it could be a vacuum leak. Fixed it - no difference.
- Cleaned MAF connectors and MAF, also wrapped a bit of PTFE round the MAF connector to make sure it's snug.
- Unplugged ESS and started engine. Not much difference.
- Checked O2 sensor data at idle. B1S2 swings between 0.8v and 0.1v in the typical way, B2S2 stays quite flat around 0.5v. I unplugged both of them to see if they were messing with the fuelling. No change to idle quality or fuel trims.
- Checked MAF live data. It showed around 4g/s but fluctuated up and down quite a bit. When applying very light throttle, it would dip to around 2.5g/s and then back up as revs increased.
- Reset engine adaptations. Seemed to make a good difference to idle quality and low RPM performance but it was back to normal after a few mins of driving.
- Finally, and what leads me to think it might be the MAF, I unplugged the MAF while the engine was idling and I was monitoring fuel trims. With MAF, short term trims were 7% - 10% as mentioned. Without MAF, both banks instantly swung to about -5%, the idle speed dropped slightly and smoothed out a bit (not entirely though), and the popping sound went away. Plugged MAF back in, trims shot up, popping returned, idle was worse.
Before I hit up autodoc for a new MAF, have I missed anything obvious in diagnosing this? I'm a novice by all accounts, and only had this car for about 7 months. Tried to use lots of info and guidance from various threads on this and other forums, and this is where I've got to. I know there are some wizards on here, so I am willing to listen and try any suggestions to sort this out.
Thanks hugely in advance!
Been trying to diagnose some rough idle and performance issues over the last few weeks (posted in here a few weeks back already). Think I may have made some progress in diagnosing and want to sense check my thoughts before dropping £££ on new bits.
Car: 2006 E86, manual, black plastic valve cover N52B30 with 163k miles
Symptoms:
- Slightly rough idle. Rpms fluctuate between about 670 and 730, seems the same whether the car is warm or cold. Seems to be a bit worse on a cold day but I could be imagining that. Tangible shake and an intermittent popping sound a bit like a misfire.
- Exhaust smells rich, especially on startup. Long term fuel trims sit at 6% both banks, short term somewhere between 7% and 10% both banks.
- Engine a bit hesitant at low RPMs, makes changing from 1st to 2nd lumpy.
What I have tried thus far:
- Replaced VVT motor gasket. It was leaking oil and I thought it could be a vacuum leak. Fixed it - no difference.
- Cleaned MAF connectors and MAF, also wrapped a bit of PTFE round the MAF connector to make sure it's snug.
- Unplugged ESS and started engine. Not much difference.
- Checked O2 sensor data at idle. B1S2 swings between 0.8v and 0.1v in the typical way, B2S2 stays quite flat around 0.5v. I unplugged both of them to see if they were messing with the fuelling. No change to idle quality or fuel trims.
- Checked MAF live data. It showed around 4g/s but fluctuated up and down quite a bit. When applying very light throttle, it would dip to around 2.5g/s and then back up as revs increased.
- Reset engine adaptations. Seemed to make a good difference to idle quality and low RPM performance but it was back to normal after a few mins of driving.
- Finally, and what leads me to think it might be the MAF, I unplugged the MAF while the engine was idling and I was monitoring fuel trims. With MAF, short term trims were 7% - 10% as mentioned. Without MAF, both banks instantly swung to about -5%, the idle speed dropped slightly and smoothed out a bit (not entirely though), and the popping sound went away. Plugged MAF back in, trims shot up, popping returned, idle was worse.
Before I hit up autodoc for a new MAF, have I missed anything obvious in diagnosing this? I'm a novice by all accounts, and only had this car for about 7 months. Tried to use lots of info and guidance from various threads on this and other forums, and this is where I've got to. I know there are some wizards on here, so I am willing to listen and try any suggestions to sort this out.
Thanks hugely in advance!
