1993 Geo Storm Engine dies when it warms up

CJNEPER

MEMBER
1993 GEO STORM
4 CYL
FWD
MANUAL
180,000 MILES

My Geo starts and runs fine until the engine gets warm, then it dies. Once it cools down, it starts and runs fine again until warm. It seemed like it might be a fuel or oxygen sensor problem, so I did a diagnostic test on the memory but there were no fault codes stored in the system. Any ideas?

5 Replies

JAMES W.

MECHANIC
2,395 POSTS

Check your "idle air control" valve. It may be carboned up or not functioning. Sounds like it is stuck in the open position where the engine will run ok when it's cold, but is getting too much air when it's warm. Also, check for vacuum leaks around the intake manifold area.

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Wednesday, December 31st, 2008 AT 1:20 AM

CJNEPER

MEMBER
7 POSTS

James,
I am checking the idle air control valve, but I do not know how to check if it is functioning. The manual says to "apply voltage" to the valve to see if the pintle retracts. What exactly does that mean? How do I apply voltage to the valve?

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Friday, January 2nd, 2009 AT 2:24 PM

JAMES W.

MECHANIC
2,395 POSTS

I need to know which IAC you have. Does the wiring harness plug directly into the IAC, or is there a short pigtail attached to it that plugs into a harness? I'm looking for letters or #s on the connector. Rither A, B, C & D, or 1, 2, 3 & 4. Let me know and I can tell you which terms and how to test.

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Friday, January 2nd, 2009 AT 8:55 PM

CJNEPER

MEMBER
7 POSTS

The four wire harness plugs directly into the IAC and has the letters ABCD on it.

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Friday, January 2nd, 2009 AT 9:12 PM

JAMES W.

MECHANIC
2,395 POSTS

OK, just what I needed. Remove the IAC from the manifold. If you put ground to terminal A on the IAC and 12 volts to term B, the pointed "pintle" valve should move out or in. Ground to term C and 12 volts to term D should move the pintle the opposite way. If the valve just jerks and doesn't move or buzzes, the valve is bad.