EGR, MAF or other

[EdmundIJones]

Hi,

I was coming back from work this evening and realised e w203 2.7CDI was in limp home mode, I only realised as it didn't rev over 3000rpm, power and smoothness were normal.

So at this point I was thinking EGR or MAF. I got home and used my generic code reader and there were no codes registered, no dash warning lights or messages either.

I took the large pipe out from the EGR and it was considerably bunged up with soot and oil, I cleaned quite a bit out as best I could without taking the EGR off completely and took her for a spin, no difference unfortunately.

No, before I take the EGR off completely is there a way to test the MAF, my code reader can check the MAF voltage and it sits steady at 8.8v when idling.

If I disconnect the MAF completely will the car automatically go into limp mode or will I be able to test the system to see if it revs freely past 3000rpm?

Any other ideas?

Thanks
Ed

 

[Dieselman]

is there a way to test the MAF, my code reader can check the MAF voltage and it sits steady at 8.8v when idling.

That's wrong, it should be ~2v at idle rising to ~4.8v at full revs and boost.

 

[EdmundIJones]

That's helpful thanks.

Do you know, if I disconnect the MAF will the car stit in limp mode or will it rev freely over 3000rpm? Maybe just rough at idle.

 

[Dieselman]

Disconnecting the MAF will make no difference to the idle, not sure about whether it will force limp home mode...probably.

 

[EdmundIJones]

What gets me is that there are no fault codes at all. Very odd.

 

[Dieselman]

There has to be a code if the ECU adopts limp home mode.

 

[EdmundIJones]

Nothing according to my generic reader that is.

 

[Buffers]

I disconnected my MAF on my C270cdi and the car went straight into limp mode also fault came up for MAF. And Dieselman is correct (as he usually is) that a fault code will display if the car adopts limp mode. Generic readers are not always that reliable. Maybe you need to have motor put on Star.

 

[EdmundIJones]

Oddly enough, I drove to work in her this morning and it was all just normal, free reving and no issues to send it into limp mode. I suspect the MAF is faulty and somehow becomes worse with warmer weather, it was 10 degrees hotter warmer last night than this morning

 

[EdmundIJones]

After spending a week driving my car in limp home mode I finally received the New MAF I ordered, fitted it in 5 minutes and instantly the problems are solved.

What has occurred to me is how good the car is in limp home mode! It drives better in this condition than a lot of other cars in good shape - just a little down of power in the mid range - I'm very impressed.

If anyone is interested, I ordered the MAF from Car Parts | Spare Parts | Car Parts Online | Motor Spares for £46 which is £10 than eurocarparts.com which is the same company.

 

[splitpin]

After spending a week driving my car in limp home mode I finally received the New MAF I ordered, fitted it in 5 minutes and instantly the problems are solved.

What has occurred to me is how good the car is in limp home mode! It drives better in this condition than a lot of other cars in good shape - just a little down of power in the mid range - I'm very impressed.

Yes, that is quite interesting, I have not yet experienced that particular pleasure but doubtless will.
It will be educational

splitpin

 

[Dblock]

After spending a week driving my car in limp home mode I finally received the New MAF I ordered, fitted it in 5 minutes and instantly the problems are solved.

What has occurred to me is how good the car is in limp home mode! It drives better in this condition than a lot of other cars in good shape - just a little down of power in the mid range - I'm very impressed.

If anyone is interested, I ordered the MAF from Car Parts | Spare Parts | Car Parts Online | Motor Spares for £46 which is £10 than eurocarparts.com which is the same company.

Did you try the mbclub discount?

 

[bobbybear]

I had exactly the same experience,Computer read by 2 indys, no idea,so with 100k on the clock i replaced the maf sensor, and cleaned the barrel.Perfect .