Car billows blue smoke out and runs lumpy... MAF issue?
Discussion
I seem to have an issue with my car (1.6HDi DS3) It runs lumpy to the point it can be felt through the steering wheel and it billows blue smoke out. However, if I take away the MAF sensor via any means it runs absolutely fine... No lumpiness, no blue smoke. I've tried running the engine a multitude of ways trying to pinpoint the issue.
If I simply unplug the connector going to the sensor, it runs fine and there's no blue smoke. If I reconnect the sensor, it will start running lumpy again and goes back to billowing smoke out.
If I disconnect the pipe going from the MAF sensor to the turbo BUT leave the sensor itself connected to the electrical system, the engine also runs absolutely fine. Again, reconnecting the pipe causes the engine to start playing up again.
I've checked all the pipes before the MAF for any oil as well as the air filter but there was none. Is this likely to be caused by a faulty MAF sensor or is there likely a bigger issue? Looking online when they go bad they usually cause black smoke due to over fueling so find it quite odd that in my case it's causing blue smoke.
If I simply unplug the connector going to the sensor, it runs fine and there's no blue smoke. If I reconnect the sensor, it will start running lumpy again and goes back to billowing smoke out.
If I disconnect the pipe going from the MAF sensor to the turbo BUT leave the sensor itself connected to the electrical system, the engine also runs absolutely fine. Again, reconnecting the pipe causes the engine to start playing up again.
I've checked all the pipes before the MAF for any oil as well as the air filter but there was none. Is this likely to be caused by a faulty MAF sensor or is there likely a bigger issue? Looking online when they go bad they usually cause black smoke due to over fueling so find it quite odd that in my case it's causing blue smoke.
AFAIK disconnecting a MAF sets the engine running on a default map with default fuelling based on a simplified set of parameters.
Based on this if you disconnect the MAF and it runs better, either the MAF, the ECU or a sensor that is bypassed in this mode will likely be at fault.
This would cause under/over fuelling.
Over fuelling will give either black smoke (complete combustion) or grey smoke (incomplete combustion) which smells like diesel as it isn't burnt.
I will stress that I am not a diesel expert, so this may not be 100% correct & I am sure others more knowledgeable than me will be along to correct me soon, it is just my understanding.
Based on this if you disconnect the MAF and it runs better, either the MAF, the ECU or a sensor that is bypassed in this mode will likely be at fault.
This would cause under/over fuelling.
Over fuelling will give either black smoke (complete combustion) or grey smoke (incomplete combustion) which smells like diesel as it isn't burnt.
I will stress that I am not a diesel expert, so this may not be 100% correct & I am sure others more knowledgeable than me will be along to correct me soon, it is just my understanding.
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