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Buick V-6 3.8 Idles Fast in Drive (But idles normally in Neutral)

...86 Buick V-6 (3.8) with 120,000 miles: idles too fast in "D"rive, BUT idles at normal speed when put in "N"uetral". TPS (throttle position sensor) had been replaced previously, and still checks OK with an ohmmeter. I could not see any obvious vacuum hose leaks. I also had the battery disconnected for awhile to reset computer. (still drives at 20 mph with foot off throtlle). Does this OK-in-Neutral provide a significant clue?? Thanks for any suggestions.

Reply to
Gene Gardner
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Reply to
Shep

You may need to give the ECM several days of driving to adjust itself if you don't closely follow the recommended relearn procedure after disconnecting the battery and replacing the TPS. You may have a real problem, but I would give it a few days anyway, then start looking for problems ie ECM codes, intake manifold vacuum leak, etc. It sounds like your IAC valve is operational since idle speed tames down in neutral.

Shep's point is a good one, too. You should make sure the sensor return wire shows about .5 volts with the key on, engine idling, throttle closed. There is a small amount of slop in the attachment screw holes for adjustment.

Toyota MDT in MO

Reply to
Comboverfish

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