Vibrations in neutral / park

[bullockandrew]

Ok, so I've been trying to solve this one for about 12 months now with no success, so any advice here will be much appreciated. All started when my '99 SL320 with 40k miles on the clock started to vibrate when stationary in park or neutral. It now turns out to be a slight misfire having checked on the STAR diagnostic system, but originally I was advised to change the engine mounts.

So the chronology is:

- engine mount change
- injector cleaner
- new plugs
- new leads
- new injectors

And still it vibrates. I have some rubbish after market CATS on the car which were on it when I bought it. They are evidently much smaller than the OEM units and are slightly rattly. Could this be the source of my problem? If so, do I need to replace with MB originals, or are there any cheaper yet effective alternatives?

Thanks a lot.

 

[television]

The miss fire could be a coil pack going down.

Re the exhaust,was the whole system changed or only the bottom boxes and pipes. Many people take the bottom cats out, and they still pass the MOT.

I have never known engine mounts to fail after 40K on any 129064 car

 

[bullockandrew]

Thanks for the reply. I should have added that I tried new coil packs all 'round too. Ouch. I bought the car 3 years ago and it had these cats fitted. Looks like the bottom box and pipes only...