The car now has around 153k miles. I've searched and have learned a lot, but most of the good threads with a lot of information come up blank when the original poster doesn't follow up.

Starting my beast is becoming an effort and is progressively worsening. Car has a full tune up: oil change, coolant temp sensor, everything related to cooling, plugs, wires, cap, rotor, coil, fuel filter, both fuel pumps, oxygen sensor, OVP Relay, and fuel/air mixture has been Mercedes master technician tuned with precision. No vacuum leaks anywhere. Fuel pressure is not a problem. I even engage the starter I click the key to on position and let fuel pumps build pressure. My fuel economy is right where is should be. Around 18-20 in the city and 23-26 on the highway. No stumbling at highway speeds.

So the problems:

Starting cold takes two tries. First crank fires up stumbles and dies. Second try takes about 5-7 seconds of cranking to get it firing regularly and it still stumbles and eventually evens out. When I step on gas stumbles all the way to 2k rpm or so.

When the car is up to operating temp and I'm driving along it stumbles and feels like it wants to stall. If I pull up to a stop and roll through and step on gas it stumbles badly. Stumbles just about any time the RPMs are under 2k. Doesn't happen all the time, but happens a lot.

Also, when at operating temperature and the car is parked and shut off for approximately 5 to 10 minutes it takes 6-8 seconds of cranking to start.

I don't know where else to look. Is the CPS (Crank Position Sensor) causing this stumble and poor starting?

Thanks a lot everyone.

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Allen Kroliczek
Oak Grove Autosport | Oak Grove Autosport
01 G500, 82 300TD, quite a few more.....