W203 C220 CDI Possible MAF Fault??

[Sirfoxelot]

I've seen a few post on here with the same issue as my car but no definitive answer

Today my W203 C220 CDI stopped reving past 3000RPM
I was told one possible cause is the MAF sensor

I disconnected this while the car was running and there was no difference at all. on my last car (A Nissan 200sx) disconnecting the MAF caused the engine to misfire like mad

I have also connected my Laptop to the OBD port on the car to check various sensor values and the MAF is showing a constant 8.4g/s across the revs up to 3000.

Is this an indication that the sensor could be at fault??

 

[Sirfoxelot]

Forgot to add. there has been no Engine management lights or fault codes

 

[turbopete]

MAF often doesnt put up lights or codes on a diesel. the reason your 200SX misfired was because it was a petrol engine.

it certainly appears that the MAF may be faulty. have you tried driving it with the MAF disconnected to see if that makes a difference?

 

[Sirfoxelot]

I havent driven it with the sensor disconnected only revved it while parked up
It runs the same as when it's connected and only revs to 3000rpm

 

[patxi]

Revving the car, even when it is not driving, should cause the flow of air into the engine to change and thus the reading across the MAF to change as well. A constant reading does seem to suggest that the MAF has gone bad.
It is possible to buy just the sensor part of the whole assembly from Bosch Auto Centres instead of the whole unit. This is a lot cheaper than replacing the whole thing but you will need a security torx bit (as the screws holding it all together have a pin in the centre of the torx star).

 

[Sirfoxelot]

Started the car this morning and it ran fine
Checked MAF readings while driving and these were around 200g/s
Went out later and fault was back. Readings now showing 8.4g/s

Have now got a replacement sensor on order

 

[turbopete]

if the car is auto, then it wont rev above about 3k rpm anyhow when not in gear. manual cars will run to about 4k IIRC