odd high idle

GMC
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CORYGILLIES
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1989 Gms Z71 4x4 5.7 Automatic.
Turns over a lot before start when cold, occasional puff of fuel smoke from tailpipe when it starts. Idle doesn't come down until driven for about 10 minutes even on hot summer day. If shut off after driving then restarted quickly, idles good, if off for 20 minutes or more idle goes high again until driven a few mins. No trouble codes, new IAC valve, oxygen sensor, distributor shaft, temp. sensor, no intake leaks.
Jul 15, 2007 at 9:18 PM
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MICKEY-D
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Does it have a carb, or throttle body?? If it's a carb, you have a choke problem, if it's injected, a problem with a temp controlled switch that richens the engine on cold starts.
Jan 7, 2010 at 3:00 PM