Lumpy idle on CDi when cold

[weebobster]

Hi gang

My year old C220CDi has developed a lumpy idle while the engine is still warming up. This has only become apparant during the recent cold spell of weather.

The routine is as follows:

I start the car and it drives as normal til I hit the traffic 4 miles from my home. The engine hasnt fully warmed up at this stage and whilst the caar is in neutral (park or drive but stationary) the idle becomes very lumpy. It sounds as if it is going to cut out but it doesnt, it just lups on til I start moving again. Now the strange thing is that by the next set of lights (a mile further on) all is back to normal for the rest of the day!

This only every happens on really cold mornings and isnt a real pain. Having said that I would really appreciate your thoughts on this one!

Cheers Bob

 

[fuzzer]

HI , we had the same on out E220 CDI . Local dealer said it was normal. Just left it at that ...

 

[weebobster]

I got a bit spooked with all posts regarding faulty MAS sensors - can I rule this out or could it be the cause of my lumpy idle???? (Im not technically minded lol)

Cheers and a :bannana: for fuzzer cuz he was in the same boat

 

[Steve_Perry]

I'm sure I've read a post by dieselman where he states that the air meter (Don't think diesels use MAS's) on a diesel can cause similar symptoms to what you are seeing. I just can't find the darned post

Maybe wait for dieselman to comment or PM him?

S.

 

[weebobster]

Cheers Steve - ill drop dieselman a PM.

Thanks for the heads-up mate :bannana: :bannana: :bannana:

Bob

 

[Dieselman]

Hi


220 CDIs can run a bit lumpy at idle due to the injectors not delivering a uniform spray. The ECU is meant to ballance the cylinders in normal running, but can't if you have a dodgy injector.

Diesels do indeed have a MAF and they can go faulty. Your car should be fitted with a Pierburg unit which are more reliable than the Bosch ones. A new one for yours is about £70.

See the thread re MAF as you can measure the output yourself with a digital voltmeter.

Firstly run some injector cleaner through the system. It does sound temperature related, but a clean out may fix it.

If it doesn't respond to treatment go to the dealer and have the fault codes read.

There have been cases of collapsed cats. but they manifest themselves by blocking the exhaust and reducing power at high speed.

 

[weebobster]

Cheers Dieselman - I really do appreciate the guidance!

Ill get some injector cleaner and let you all know how I get on.

Bob

PS: it is wee helping hands like this thay make MBClub the only show in town :bannana: :bannana: