R230 SL350 rough tickover

[H1 NPW]

The tickover on my 2007 SL350 does not seem as smooth as I think a V6 should be...

My local MB independent diagnosed that a couple of coils were on their way out (mileage 60K) so had them all replaced... no noticeable difference.
The plugs were replaced at 55K.

Any thoughts as to what the issue might be?

 

[grahamcol]

What's the condition of the plug leads like ? Given you've chaned the plugs that's where I'd be looking. Sometimes they can look ok although they're past their best.

 

[John Laidlaw]

^ good call

 

[Blobcat]

Also worth a check that your engine isn’t suffering from the balance shaft issues that some M272’s have. Star can diagnostics will show up any of the error codes.

 

[ajlsl600]

some kind of vacum leak , inlet duct leak does it run ok other than at idle ?

 

[LostKiwi]

Check the short and long term fuel trims. Might give some clues.

 

[H1 NPW]

Yes, it runs fine apart from the rough idle.
Fuel trims.... what are they?
Cheers
Nigel

 

[LostKiwi]

Fuel trims are stored in the ECU. They are the amount the car is injecting compared to the map in order to satisfy the lambda sensor feedback. You need a code reader to see them.

 

[ajlsl600]

check all the simple as mentioned previously stuff first. from what you say ? there is no issue ,or none yr aware of above idle. then go double check areas where yr or others hands were last. following that, and no solution get a diagnostics check,preferably on a star system.
you may find some of this interesting, think this yr eng. ??

http://australiancar.reviews/mercedesbenz_M272.php