2.3L ('83-'97) Stumble at Idle

[JW20]

Hey everyone,

My 97 2.3 5-spd with ~190K miles has developed a strange issue that just appeared suddenly with no other symptoms. When coming to a stop, the RPM will drop for 3-5 seconds and the engine will idle very rough and almost stall. Then it just goes away and idles fine until I take off and come to a stop again. It's enough to where the voltmeter dips down and the headlights will dim. The alternator was replaced earlier this year, as was the battery. AC is not even connected anymore (used a shorter belt to bypass it), and nothing else is running; not even the fan. I pulled the intake boot to look at the throttle body, it looks spotless as does the MAF sensor. I'm not really sure where to start looking. Any ideas?

 

[alwaysFlOoReD]

IAC valve. (Idle Air Control) Not sure where it is on the 2.3. When you find it pull the wire connector off and idle should slow or stall out. This is good. If needs replacing use ford oem.

 

[JW20]

IAC valve. (Idle Air Control) Not sure where it is on the 2.3. When you find it pull the wire connector off and idle should slow or stall out. This is good. If needs replacing use ford oem.

Awesome, thank you. I was able to easily find it once I knew what it looked like. For anyone wondering, on this generation of 2.3, it's near the throttle body almost touching the firewall.

I unplugged it while the truck was running and it immediately stalled, like I'd turned the key off. What does that mean? Any other way to diagnose before I spend the money on the part?

 

[alwaysFlOoReD]

Immediate stall means it's working as it should. I'm not sure where to go from here.
Edit. It could possibly be sticking which could cause the problem you describe. Remove and clean with carb cleaner or brakleen and reinstall, see if situation improves...

 

[JW20]

Immediate stall means it's working as it should. I'm not sure where to go from here.
Edit. It could possibly be sticking which could cause the problem you describe. Remove and clean with carb cleaner or brakleen and reinstall, see if situation improves...

The IAC valve gave me something to go on. I looked up other symptoms and someone described another issue I didn't know was related. If I switch on the AC, even though it's not physically connected anymore, the idle will hang. In a manual it was almost like cruise control. You could turn the AC on and take your foot off the pedal and it would keep accelerating. I just figured it was the computer compensating for the added load of the AC compressor.

As it turns out, one of the symptoms of a failed IAC is high idle when the AC is switched on. I went ahead and ordered a new IAC valve. Hopefully this does the trick. Thanks again!