I have a 93 190 2.3. When you start it first thing in the morning, it idles high at about 1000. It will stay that way if you drive it for an hour or four hours. If you shut it off and let it sit even a few minutes, it will idle almost normal but a little rough. When I bought this car it would idle at 1200 no matter what you did. Having access to cheap parts, I've replaced the ovp, the icv, the eha, the 02 sensor, and the throttle position sensor. It seems like whatever I correct will last for a day or so and revert back to high idle. Now that it's warmed up here in Pa., it want's to idle so low that it stalls after it's second start of the day. I tweaked the mixture a bit and it stays running. I've done the propane testing for vacuum leaks and found nothing. Just an FYI, this car storms from the line and runs excellent. Plenty of power and about 21 mpg. Someone told me that the air temp sensor might do these things - I don't know but doubt it. Any ideas?

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Andy
71 350SL (sold), 81 380SEL, 84 300D (just sold), 85 190D (sold), 91 300E, 93 190E (just sold), 79 240D (sold) , 83 240D (living on in my other cars) an 83 380SEL (sold) 82 380 SL and 85 300D. Just bought a 95 SL500.

Before spending any more money, I would check and verify that the Throttle Micro Switch is adjusted and working correctly.

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

That was replaced as well. It's been tested and is working fine. Thanks for the input though, Andy

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Andy
71 350SL (sold), 81 380SEL, 84 300D (just sold), 85 190D (sold), 91 300E, 93 190E (just sold), 79 240D (sold) , 83 240D (living on in my other cars) an 83 380SEL (sold) 82 380 SL and 85 300D. Just bought a 95 SL500.