Hi Everyone, I have a 98 ML320 with 225000 miles.
Coming home the other night my check engine light came on when passing someone. My Ml started running rough and had no power. I borowed a scanner and came up with these codes. P0300, P0301, P0303, P0460 (Fuel gauge has been erratic for some time). Over the last couple of days, just about every cyl has been hit with a missfire code. Looking over other threads, most missfire problems seem to have been the crank position sensor. I replaced it today and it didn't help. If I turn the truck off and then restart it, it seems to run ok for a while. Then the cel flashes and it runs rough again. Above 4000 rpm it misses badly. Any ideas on what to check next? Thanks for your help.
Howard

Have the spark plugs been replaced? How about the coils?

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Hi pawoSD,
I replaced the plugs about 10000 miles ago. Its been running fine till the cel came on. I wouldn't think more than one coil would go bad at the same time. Might not hurt to check the plugs though. Thanks,
Howard

Typical for the M163 is the MAS going bad. That manifests symptoms such as hard starts and extremely poor acceleration performance.

I let mine run like crap for over six months before it finally ate the fuel pump too!

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Hi G-Benz,
I haven't had any trouble with hard starts, got to admit though the acceleration wasn't great. still looking, thanks.
Howard

I had similar things on my 1998 ml320 - misfire all cylinders on driver's side. bad performance at rpms higher than ~3k.
changed MAF, spark plugs, wires - it did not helped
finally replaced driver side cat and o2 sensors - problem solved.

Excessive exhaust back pressure is a good possibility.
Having the backpressure checked would be a good starting point.

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