1994 Dodge Stealth keeps stalling at idle when warmed up, why?

I have a 1994 Dodge Stealth (base model) with a 3.0 SOHC V6 Mitsubishi engine and automatic transmission. Recently, my car would often stall when idling after it's been fully warmed up. It runs fine when it's cold, has no
problem starting up, runs smooth and has plenty of power when cruising or accelerating, and I have not noticed any drop in gas mileage. But after I've been driving it for about 10 minutes and the engine's reached it's full operating temperature, when I come to a stop the engine starts stumbling and running rough, and the RPMs drop and it stalls out. I thought it might just be a case of bad watered-down gas, but after 2 tankfuls later from different gas stations and 4 bottles of Drygas (fuel drying additive) it's still doing it. It hesitates and stalls even when I slip the transmission into Neutral or Park. For the time being, I've been able to keep the engine from stalling by turning up the idle screw, but it still often runs rough at idle so it's not a permanent fix. Also, my "check engine" light does *not* come on.
Maintenence info: Within the past 20,000 miles, I have replaced the fuel filter, timing belt, spark plugs, plug cables, distributor cap and rotor, battery, and just recently the air filter.
Thanks for any tips!
- Logic316
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When was the throttle body and AIS last cleaned? Any error lights or codes?
Bob

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I am not getting any "check engine" light or any other error lights on my dashboard. All the guage readings look normal. I did spray carburetor cleaner in and around the throttle body only 500 miles ago, and everything looks pretty clean in there. Somebody in another group suggested that it might be a worn oxygen sensor, but I took all three of them out, cleaned and tested them on a voltmeter about 5000 miles ago and they were working fine. I would also think my gas mileage would noticably suffer and I would probably get a check "engine light" if any of those were the problem, so I doubt it.
- Logic316
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On 2/19/2008 2:35 PM, Logic316 wrote:

My best _guess_ right now would be a vacuum leak. You might be able to hear a hissing sound as the engine dies. Feel for a vacuum hose that is soft and/or collapsed. Sometimes the collapsed section of hose will have slit broken open in it. A hose could also be cracked where it fits on the barb fitting.
A second guess: Throttle Position Sensor. Probe the connector at the middle position with a digital voltmeter. Sweep the throttle through it's full range. The voltage should go smoothly from about 1/2 volt to nearly 5 volts. Any sudden dips (especially all the way to zero) indicate a fault.
I hope this helps but sometimes eliminating what is _not_ wrong is nearly as helpful :-)
--
G. R. Woodring

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On Tue, 19 Feb 2008 14:35:26 -0500, "Logic316"

The fact that it runs OK when the engine is cold is because the ECU enriches the fuel mixture until the engine reaches operating temperature.
Your 'shitty box is trying to tell you that it can't adjust its idle speed. The idle speed is controlled by an automatic idle speed control valve which is an electro mechanical business controlled by the ECU. These things get dirty and also wear out. Remove it from your 'shitty box and squirt copious amounts of carby cleaner through it until it runs clean and then squirt some automotive grade ghee into it for lubrication.
I seriously doubt that you can test an O2 sensor with a multimeter (all that will do is test the circuits internal resistance). To test one you need to see the signal it produces when it is at operating temperature and subjected to exhaust gas!
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