Everything was perfect this morning, car started and ran without any problems. Park at work come back out 9 hours later. Start the car, it idles really bad. Like 5 cylinders. I give it gas, no reaction for 3-4 seconds then sort of catches and surges and inmediately lets go (some sort of popping sounds coming from engine compartment). It did it several times before it idled normally. Drove home 15 miles without problems (65 mph steady). I get to the first light, no problem. When starting to give gas same thing again, no response when given gas, then all of a sudden (popping sounds) surges and runs without problems. I get home and park it idles like crap again, in neutral, park, reverse, drive. I give it gas it does not responds, it hesitates, shakes, pops and it revs up again normally and idles ok. I go for a drive, in the beginning it hesitates,pops, almost dies, revs up tires screech and runs and idles like a champ. Come back home idles OK, shut-off, start again and no problems. Go out 2 hours later no problem. What will tomorrow bring? Done Very recently: Oil and filter change every 2500 miles (religiously) Done recently (within 6 months or 15K miles): New OVP, New coil, sparks, distributor, rotor, air filter. Recently went from NY to Fl back to NY and now NC, ran fuel injector cleaner-techron. Done not too recent (30K miles ago): Wires, fuel filter Any suggestions-advise-possible diagnosis?

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

I would suspect water in gasoline, clogged fuel filter, fuel pump or fuel relay, ignition problem (distributor cap/rotor, coil)
Good luck
JackD

I would also suspect a defective mass air sensor.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

It worked very well today, with one exception. When back from work (engine at normal operating temperature 87C), the car did not go back to normal idle (approx. 650-700 RPM in park or neutral). It sort of oscillated between 500-900 RPM for about 15 seconds before settling at normal. It did it several times, in intervals of about 3 minutes.
What should I look for?

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

A fluctuating idle like that sounds like a faulty mass air sensor, or a vacum leak.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Idle air bypass valve? If it is sticking closed and/or open, it can cause the problems you describe. They get clogged up and stick. Sometimes a good cleanining with carb cleaner is a good (though temporary) fix to see if it is the problem.