Engine Performance problem
1991 Chevy S-10 4 cyl Two Wheel Drive Manual
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The engine idle will often race at a very high idle even after the engine is warm. It idles fast enough to maintain 40 mph in third gear without touching the accelerator. This engine only has about 30,000 miles on it. We have checked the cable and throttle and nothing is sticking. We also recently changed the temperate sensor at the water pump.
Any Ideas?

Check for vacuum leaks with carb cleaner, spray around carefully, if the engine changes, you have found a leak, if nothing it could be a sticky Idle Air Control Motor (IAC)