Did a search but couldn't find anything specific on my problem. Bought a 99 SL2 with 140000 miles. The car would die at stoplights unless I kept it reving. So I seafoamed the engine and cleaned the PVC and Throttle body with carb cleaner. The engine no longer dies but the when driving and taking foot off of the gas the rpms do n ot go down, they stay at the same level (have tested this for a whole block with foot off). The only go down when using the breaks. Where should I start with this?

Check the engine coolant temperature sensor, the original ones are plastic tipped, prone to cracking and causing either a lean low idle or rich high idle problem. Replace it with the brass one and check the two-wire connector for corrosion otherwise replace it either from a junk yard intake air temp sensor connector or the dealer's $30 replacement. Don't overtighten the sensor.

OK I changed the collant temp semsor. It seems to have smoothed out the idle, but another problem is the car dies at stoplights, only when the A/C is on and only in drive or reverse. I was thinking of changing the TPS and cleaning the Idle Air valve. Anyone have other ideas?

Could be the fuel filter/regulator. On the 2000 SL2, the regulator and fuel filter are one part. The best price I found was at NAPA for $50. Hopefully tou are luck and the filter and regulator are seperate.

you may want to check into a crank position sensor or the idle air control valve. my 97 sl2 had the same problem. i installed those parts and the idle problem is gone.

Is crank position sensor the same thing as throttle position sensor? I have the part and was planning on replacing that and cleaning the idle air control. If its not the same thing were is the crank position sensor located. And I plan on changing the fuel filter very soon.

The cps is different from the tps; the cps is located above and behind the starter with one 10mm bolt, the tps is on one side of the throttle body opposite the throttle linkage. With the engine in idle rap the tps with the butt end of a screwdriver; any change of rpm indicates that the tps is faulty and needs replacement. The cps is more important to engine operation; it controls the ignition/spark system, allows the fuel pump to run, and the injectors to pulse. No cps operation = no ignition, no fuel pump, and no injector pulses, a dead engine. The typical symptom of a faulty/failed cps is that you can crank the starter all day until either the battery dies or the starter burns out but the engine won't fire up. Sometimes it will work and then not at the most inconvenient moment. You don't have this symptom but may have a sticking/faulty idle air control valve (IACV). The iacv is on the throttle body and adjusts the idle speed. If one of the two precision servo motors is sticking or faulty the engine may never idle/run at the right speed, either always high or low, erratically changing rpm anytime. Clean with electronic contact cleaner only.

I changed the TPS and cleaned the IACV. No change in operation (other than a smoother accel.). The car still dies in drive and reverse sometimes with the a/c on. Ive made a conection that it only does this on hot days (almost everyday here in FL). At night its not a problem. Also got a service light (code was: system too rich, bank one). Is this connected to the car dying?