W202 C180 engine shaking at idle?

[horatio]

I have replaced the engine mounts with Lemforders, fitted new spark plugs (NGK non-resistors) and removed/cleaned the throttle body.

Disconnecting the MAF at idle makes no difference at all (?).

It drives really well and idles nicely at 700 ish. I can't see any obvious vacuum leaks.

Any thoughts on what I can check before admitting defeat and booking into an Indy?

Cheers!

 

[John Laidlaw]

Engine mounts?

 

[LostKiwi]

I think you need to get codes read on a proper diagnostic machine (Star).
If that shows nothing live data readouts may.
From the description it does sound vacuum leak related.

 

[Steve@Avantgarde]

If the engine is shaking, are you describing a misfire?

Sounds like you are throwing a lot of parts at it here without actually doing any solid diagnosis. An indie would be the best idea from this point.

 

[horatio]

It must be a slight miss. The old mounts were worn out (originals at 143k!) and leaking oil so I thought the idle vibration was simply that.

A few spark plugs and a can of carb cleaner hardly broke the bank so I'm not too far in at this point!

 

[horatio]

Well I removed the ignition bits & bobs. Hairline cracks in both coil pack cases, the rubber boots on the coils & leads all very cracked/perished. Hopefully refreshing these will fix it. Even if not, leaving it all in this condition is surely asking for trouble.

 

[Valton]

I have replaced the engine mounts with Lemforders, fitted new spark plugs (NGK non-resistors) and removed/cleaned the throttle body.

Disconnecting the MAF at idle makes no difference at all (?).

It drives really well and idles nicely at 700 ish. I can't see any obvious vacuum leaks.

Any thoughts on what I can check before admitting defeat and booking into an Indy?

Cheers!

I will try to explain this problem on M111.921 engines, even though this post is old. I hope you have fixed the problem. Mercedes engines use a mechanism for changing the valve timing, this is so called phase shifter, it is mounted on the intake camshaft and it's controlled by a magnet. When voltage is applied to the magnet then it pushes the spool. Over years the spool and magnet can jam and then the shaking problem starts to show. It can also be the MAF sensor not reading the correct voltage, also the throttle body plug wires are burned/shorted. Cheers!

 

[mioba]

Holy thread resurrection