99 Caravan stalls when cold

[chevypanel52]

My '99 Dodge Caravan, 3.8 litre with about 220,000 km on it, stalls when very cold (i.e. less than 10 degrees C/50 F ). It just plain will not run without my foot on the gas pedal. Once it's warm or on a warmer day it runs fine. Have replaced ignition wires, plugs, cleaned the throttle body, etc. etc. Any ideas what to look for or tell my mechanic to do? Thanks !

[RIP]

The idle air control (IAC) valve controls engine idle. It's driven by the powertrain control module. It's mounted on the bottom of the throttle body and controls an opening there just aft of the throttle plate to allow air to enter the intake manifold with the throttle plate closed. When you press on the gas pedal, you're opening the throttle plate, allowing air into the intake manifold. It's not clear why all is well when it's warmer but, I would look in that direction. The IAC may be sticking when cold. Might try removing it and cleaning it and/or it's connector with electrical contact cleaner.

Are you seeing a service engine light? Notice any hesitation, stumbling at speed? Other possibilities: engine coolant temp (ECT) sensor, upstream O2 sensor.

http://www.autozone.com/shopping/rep...00c1528003c4be

[chevypanel52]

Thanks, RIP. I'll try the IAC first. Where is the ECT ?, if the IAC isn't the problem.

No engine service light at all, no hesitation or stumbling at speed, even when cold.

However, occasionally the revs drop significantly when I take my foot off the gas when at highway speeds (say 60mph, at 2800 rpm, revs drop to 800 when foot taken off gas, then rebound back up to 12 or 1500) ... may or may not be a related problem.

Thanks for you suggestions.

Peter

Originally Posted by RIP

The idle air control (IAC) valve controls engine idle. It's driven by the powertrain control module. It's mounted on the bottom of the throttle body and controls an opening there just aft of the throttle plate to allow air to enter the intake manifold with the throttle plate closed. When you press on the gas pedal, you're opening the throttle plate, allowing air into the intake manifold. It's not clear why all is well when it's warmer but, I would look in that direction. The IAC may be sticking when cold. Might try removing it and cleaning it and/or it's connector with electrical contact cleaner.

Are you seeing a service engine light? Notice any hesitation, stumbling at speed? Other possibilities: engine coolant temp (ECT) sensor, upstream O2 sensor.

http://www.autozone.com/shopping/rep...00c1528003c4be

[RIP]

The ECT is just aft and slightly right of the thermostat housing. Follow the upper rad hose to the engine. The hose connects to the thermostat housing.

One thing to try is hold a hair dryer on the individual parts a few minutes before a cold start. Might be able to nail the culprit.