C 240 MAF sensor

[pace]

Hi all, you may remember my previous posts about my whistling car and battery problems. Well the car now seems O.K. but the gear change can be rather jerky. I have taken the car back to the garage which serviced it and they have cleared a variety of fault codes which may have been caused when the battery was replaced, but they said if the car starts to play up again it allmost certainly needs a new MAF sensor. Is this a fair diagnosis or are they trying to extract more of my hard earned? How much should a mew sensor cost? and can I clean or repair the existing one? the car is a 1999 C240 auto saloon.
Many thanks,
Paul.

 

[television]

The car normally needs a new MAF when the engine goes into limp home mode.

Check the threads out at the top of engine section.

malcolm

 

[Glenn Smith]

The car normally needs a new MAF when the engine goes into limp home mode.

I have changed many mass air sensors, not once had any gone into limp home, but just showed a drop in performance, when checked on diagnostics no fault is recorded either, however when actual values have been checked they have been reading incorrectly i.e. they show less air than is actually going in and therefore put less fuel in. I would point out that this has been on VW engines althogh i doubt mercs are any different.

 

[RCLORLEY]

I recently had to have the maf sensor on my A class replaced . it juddered as if it was in the wrong gear when driving but never went into limp mode. I ended up having to have a new ecu at a cost of £933

 

[television]

I have changed many mass air sensors, not once had any gone into limp home, but just showed a drop in performance, when checked on diagnostics no fault is recorded either, however when actual values have been checked they have been reading incorrectly i.e. they show less air than is actually going in and therefore put less fuel in. I would point out that this has been on VW engines althogh i doubt mercs are any different.

With MB many go into the limp home mode with a faulty MAF,on a fault read out it will mention everything other than the MAF, as the other components have deviated from there stored settings to compensate. So long as the engineer can work this out, its fine,but so many cant and they start changing everything.
We have had many threads on this subject. As mentioned in the trade journal 3 months back that fault codes are only of use if the engineer knows what he is doing.

Malcolm

 

[pace]

Update - I removed the MAF sensor today, I inspected the sensor housing and ducting and it was all completely clean. I then used some air intake cleaner and gave the sensor a good spray, shook it dry and re installed it. I must say I have noticed quite a marked improvment, the car seems to have more power and the gear change is much smoother at high revs also the kick down seems less hesitant. hopefuly I have sorted it but I will need to give it a good run to make sure. It seems odd that such a minor component can have such a huge affect on the running of a quality car.
Paul.

 

[veedweeb]

Update - I removed the MAF sensor today, I inspected the sensor housing and ducting and it was all completely clean. I then used some air intake cleaner and gave the sensor a good spray, shook it dry and re installed it. I must say I have noticed quite a marked improvment, the car seems to have more power and the gear change is much smoother at high revs also the kick down seems less hesitant. hopefuly I have sorted it but I will need to give it a good run to make sure. It seems odd that such a minor component can have such a huge affect on the running of a quality car.
Paul.

There's a thread on here somewhere about cleaning MAF sensors.

They tend to get contaminated with grease, which damages the VERY sensitive plate inside them. Cleaning a dirty MAF can restore it, but sometimes they are too far gone and have to be replaced.

I'm not sure what the intake cleaner is that you used, but certain cleaning products can actually make the situation worse. You need to be using an electrical component cleaner, and it has to be one that dries without leaving any residue. Isopropyl Alcohol is ideal.

Like I said, I don't know what the stuff is that you used, but if it's worked, that's good

I changed the MAF on my C240 and it made the world of difference. For about a week until a lambda probe failed

I've heard since that changing the MAF can cause lambda probes to fail, but I'm not sure about that. I wouldn't be surprised