idle problem

[Jim Ferraro]

Hi i have a 1991 420 sel and i have just got a new idle ait control valve and the idle is now fine but the engine is shaking real bad any ideas? it has a new tune up dis cap and belts

 

[talbir]

Hi,

Have you checked plugs and leads ?

Was the shake there before you replaced the idle control valve ?

Otherwise, you may have an air leak somewhere or car may be too lean in mixture.

 

[Jim Ferraro]

thank you for your reply
I got a tune up on the car new dis cap and spark plugs do you think i should have gotten wires also ? being that the idle control valve made the car race it did not shake i see that when the oil pressure is at 3 and and at an idle it does not shake but when i use it and i let it idle and it goes to 1 it shakes i am going to look for a air leak and check the mixture ... the mixture is adjusted by a allen key right ? thanks for your time ! I am going to bring the car to a man from Germany who works on only mercedes see what he says i would like to get the timeing chain done and maybe a valve job because the car had blow bye should i use synthetic oil?

 

[talbir]

Another thing is to check the spark plug gap.

Which plugs did you put in ? You should use Bosch W7-DC gapped at 0.04".

Don't use Champion or platinum or any other rubbish. The Bosch W7 have the correct heat range for your car.

Yes, the mixture/CO is adjusted by a 3mm allen key - but I reccomend you have this done by a proper MB technician, with the car hooked up to a machine via the X11 diagnostic port. A rich/lean mixture will cause rough idle, so worth eliminating this before further diagnosis.

If you have blowby, then do not use synthetic oil. Use Castrol 15-40, at least until you have replaced valve seals.

 

[Jim Ferraro]

Thank you!

thank you very much I made an app to bring the car to Mercedes for the idle... I am going to see what kind of spark plugs they put on the car you are deff right about that, thats something i didnt think of thank you very much for all your help it means a lot