Rough Idle C220cdi W204

[Athienou]

Hi!

Have a 2010 220CDi. Went to local mechanic with a Coolant issue. Said it was the Fuel Filter housing.
Apparently a common problem. He repaired the leak but ever since the car seems to have rough on idle. Idles fluctuates from 820 to 860 revs when stationary. Is this normal?

It got extremely bad and I returned to mechanic. He said it was a Injector seal. He showed me the bad injector hissing away. He changed the seal but the car still has a rough idle.

Would be grateful for any advice

 

[BlackC55]

It could be a number of things.
Has the air filter been changed recently? It could be clogged and this can cause hunting. It may need the adaptions re-set on a Star after the filter has been changed.

 

[horatio]

I had this on the CLK a few years ago (different cdi engine) - the culprit was the fuel pressure regulator. It caused no fault codes. One specialist recommended replacing all of the injectors. Another tried replacing one (with the worst value) which bizarrely solved it for a month or so. The part was £50 and took 5 mins to swap.

Maybe something to consider if all else fails.

 

[ToeKnee]

It could be a number of things.
Has the air filter been changed recently? It could be clogged and this can cause hunting. It may need the adaptions re-set on a Star after the filter has been changed.

Is there a list of cars/models that need the adaptations reset after an air filter change? Just wondered whether it was needed on my R231 SL500?

 

[BlackC55]

Mainly diesels only. They are sensitive little buggers these days.