Just wanna run this by you guys. If cold started, all is well. In fact, this morning I forgot about the issue as I got in an took off. But once warm and restarted, I can stall the car if I wish to just by pressing the accelerator most if not all of the way. It runs like pure crap. Then, as if a switch is flipped, she run just fine. Cherps second in fact (if I really wanna push it).

This is very repeatable. The time from a hot start to "im fine now" is probably less than a minute. Revving the engine slightly helps. (it will not go much past 3k anyway).

I feel its an O2 sensor issue. Or maybe the idle air control valve thing. This was a sudden issue that came up with no warning at all. I have not dived into things yet but I wanted your input incase this is an issue seen before. Then I will go from there.

Thoughts? Any help is appreciated!

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Good idea to check all HT issues: leads, caps, rotor arms and plugs. Only use the best quality parts; MB or Buru/Bosch ONLY.

Yours probably (like mine) demands ordinary, cheap, copper spark plugs from Bosch/Beru/NGK.

Then ensure there are no vacuum leaks into the inlet.

Once that's done, start thinking about fuel and control issues.

RayH

I too have had this trouble on our 420SEL, 1990. after checking the electrical parameters of the EHA and the fuel mixture and the ox sensor it began to run better. If you can have your fuel system checked to see if upper and lower chambers are set properly, I recently performed all this on one of our cars. once your car gets into the idle area warmed a finner fuel balance is needed, you may wish to check the engine temp unit it could be giving off a bad signal, though I lean more toward fuel settings.

If it was fuel settings, I do not see how it would suddenly adjust and run fine. I can check lambda. I will be its off. I just find it odd it corrects itself. If idling, the car will actually rev up fast for a second and settle down. Thats now how I know the car will now run normally.

__________________
1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

I'm not intimately familiar with the V8's, but I would find the service information for checking the coolant sensors. There should be one for the FI and one for the guage. That would be the first thing to check and with the information in hand, will be a quick and easy check. If the sensor is good, don't overlook inspection of the sensor wiring.

Thanks Air, I will do. In fact, they are original and not expensive. Probably worth just replacing anyway.

I am not sure if the problem is really gone, so I will proceed as if its not. But no issues today after 3 hot starts. Not even a hint. So much for being repeatable. I may have to look at some connector being loose also. If I find anything, I will update.

__________________
1991 560 SEL / 185k miles
1992 750il / 17k miles - project car