1991 Geo Prizm engine

1991 GEO PRIZM
138,000 MILES • 4 CYL • FWD • AUTOMATIC
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SPICIMA
  • MEMBER
  • 3 POSTS
When my engine is'nt warmed up my car idles so hard and low it cuts off sometimes.but when the engine warms up or im running the air conditioner or heater it runs good again.what does this problem sound like?
May 22, 2008 at 10:15 AM
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MMPRINCE4000
  • CAR REPAIR CONTRIBUTOR
  • 8,548 POSTS
The idle air control valve is bad or possibly the throttle body is full of debris. Also check the PCV valve.
The AC commands the engine to add more power since it requires more power to run, the heater (if in defrost mode) will cycle the AC on and off.

The best thing to do is to use a scan tool to isolate the sensor with the problem ( assuming the engine is in good tune).
May 22, 2008 at 5:40 PM
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