Hello again. Question on my 92 500sl with 65k miles.
When I first start the car, it feels like the engine shakes/rumbles for the first 3-5 seconds. This happens
almost everytime i start the car, cold or hot. The
RPM is about 1000 when first started then drops to about
500/600 when warm.

If I recall correctly (?), the problem seemed to first occur
when it ws cold, but now it seems to happen when both cold
or hot.

After the first 3-5 rough seconds, the idle is very steady
and smooth, especially in gear.

Over the past 12 months, I've had new motor mounts, caps,
plugs, gas filter, and 60K mile service.

Any assistance would be greatly appreciated!!!

THANKS!

I hope you replaced the distributor rotors with the caps.

I have had a few fuel injectors fail and drain the fuel pressure resulting in rough starting.

Thanks for the reply!

I don't believe the rotors were replaced at the
same time as the caps. You seem to suggest this
is/maybe a problem; what is the issue with doing
the caps without the rotors?

Also, on the possible bad injectors, how is
a bad injector diagnosed?

Again, THANKS for the help and your time!!!

Could be carbon buildup-when the car's cold, any carbon in a cylinder, as I understand it, acts like a sponge and absorbs some of the fuel. This changes the mixture to lean, and therefore causes the car to stumble.

I had this problem with my M119 V-8, and a couple of cans of BG 44K took care of it. Good luck!

any other suggestions? again my problem is:

cold start: engine shakes/rumbles for 3 seconds

warm start ( engine shut off for greater than
15 minutes) :engine shakes/rumbles for 3 seconds

hot start (engine shut off for less than
15 minutes): no problems


THANKS!!!!

Same problem in 1991 420. Mechanic says it is probably a leaky injector.

Sounds almost exactly like fuel injectors. ESPECIALLY in a cis-based engine like yours with such low mileage. I'd replace them all (around $220 and piece of cake to do yourself).

Satish
1989 560SEC - M119 32V