S430 Idle problem, engine dies intermitantly
 

I have an intermittent problem with the idle of the car. Every so often when the car comes to a stop the engine will die. The computer does not have any codes in it. The car has 100,000 miles on it. The spark plugs have 20,000 miles on them. The intake manifold shows no leaks when smoke tested. I find no carbon build up at the throttle plate ( possible restricting the movement of the throttle plate and causing the problem ). Moving the wiring harness back and forth does not effect the cars idle. I do find some random misfires on all cylinders in the live data of the computer but not sure what if that is related to the idle problem. Not sure what to check next? Any ideas out there? Thanks John

Couple of random thoughts -
Any air leaks to MAF?
What type of plugs did you replace with?

Reply
 

Double platinum plugs, and no air leaks upstream of the MAF.

Dump your platinums and put the OEM plugs in. Lot's written about this Search the forum (M113 + plugs)

Your throttle body is probably dirty,The throttle body has a hose from the air filter housing attached to it,the throttle body is attached to the intake phlenum.Take the hose off(its rubber with a clamp on it).Do this with a cold engine,NOT RUNNING ! spray some carburator cleaner inside the venturi and scrub it with a toothbrush,on the side of the throttle body there is a place where a cable goes into,twist the direction of cable to open the throttle plate(inside the throttle body),and continue to clean.

He said he already checked the throttle plate...

I second the spark plug idea...those Bosch Plats are junk, get the proper OEM ones, preferably from the dealer. That alone could very well be causing your problem.

When you say "the engine will die", do you mean that it stalls, and you have to re-start it??? If so, it sounds like you may have a bad CKP sensor.