ML430 misfire

[nztankman]

Hi team

I have a 2000 ML430 done 130k kms (about 80k miles). Recently it has developed a misfire in cylinders 5 and 7. It starts on 8 cylinders, although at idle runs a little rough, then after a minute or so develops the misfire, and shuts down fuel to the 2 cylinders in question.

So far the technician who is trying to locate the problem has changed the sparkplugs, coils, and HT leads. He has checked the compressions, all of which are well within tolerances, valves, lifters etc. It doesn't rattle in the top of the head so we have largely ruled out a mechanical issue.

Has anybody encountered a similar problem or has a suggestion of where we should look next?

Thanks in anticipation.

[eric242340]

Originally Posted by nztankman

Hi team

I have a 2000 ML430 done 130k kms (about 80k miles). Recently it has developed a misfire in cylinders 5 and 7. It starts on 8 cylinders, although at idle runs a little rough, then after a minute or so develops the misfire, and shuts down fuel to the 2 cylinders in question.

So far the technician who is trying to locate the problem has changed the sparkplugs, coils, and HT leads. He has checked the compressions, all of which are well within tolerances, valves, lifters etc. It doesn't rattle in the top of the head so we have largely ruled out a mechanical issue.

Has anybody encountered a similar problem or has a suggestion of where we should look next?

Thanks in anticipation.

Clean the fuel injectors and replace the fuel filter.

[nztankman]

Thanks Eric

Should of added that we have done the injectors - not sure about the fuel filter, will check with my techo.

Cheers

[eric242340]

Originally Posted by nztankman

Thanks Eric

Should of added that we have done the injectors - not sure about the fuel filter, will check with my techo.

Cheers

The missfire only happens on the same two cylinders? Was this missfire on the same cylinders before the coil/spark plug change?

[nztankman]

Thanks Eric

The misfire was on the same two cylinders (5 & 7) both before I changed the sparkplugs, coils and HT and after. The injectors have been cleaned, they were injecting the correct amount of fuel but some had an irregular spray pattern.

Thanks

[eric242340]

Swap the injectors from 5 and 7 with 1 and 2 then see if the missfire moves to 1 and 2 or is it still 5 and 7.