2002 E430 - Occasional miss at idle...no codes?
 

My 2002 E430 seems to have an occasional miss at idle - for example, while stopped at a stop light the engine will stumble/miss maybe once or twice per minute.

There are no warning lights or malfunctions, but I took it to the dealership when it first started occurring (~3 months ago) and they of course couldn't reproduce it and said there were no malfunction codes in the computer.

The miss has gotten worse over the last month or so - any ideas on what it could be?

FWIW the car has 77k on it. Spark plugs were replaced at 60k.

Misfire
 

Most likely problem exists in the wires but finding the culprit will take a little time with a ohmmeter 2.2Kohms per wire only allowed a 10% deviation

Where would I connect the ohm meter to measure that resistance?

You would be removing the plug wires and measuring them end-to-end.

Your car is at just the right age & miles for the plug wires to be getting a touch flaky. About 7 years is how long the M112/M113 wires seem to last. Idle quality degrades first, though it takes a while to throw a code.

I had the same symptoms on my 2001 E320 - an occasional, single stumble at idle. The problem was somewhat correlated with wet/humid conditions.

Replacing the plug wires eliminated the occasional stumble.

- JimY

I have a stumble under load that one mechanic said is plug wires and another said is fuel injectors . How do I differentiate between the two?
Car is a 93 400 SEL