Truck Trend Garage: High-revving 1994 Chevy S-10
Question: I have a 1994 Chevy S-10 pickup and whenever I let off the throttle, the engine revs on me. It usually doesn't matter what speed I'm going when I let off the gas. When I start it up, it initially idles high, then evens out. When I drive the truck--more noticeably on the highway--and reduce my speed by letting off the accelerator, it revs. It's difficult to slow down. The check engine light came on a few months ago, but not since. I don't have the rpm on the dash, so I'm not sure how high it goes.
Answer: First and foremost, the system needs to be scanned to determine the trouble code. You want to repair the cause first because it may very well be related to the high rpm. Possible causes of high rpm are a vacuum leak, the throttle cable/ throttle plate hanging up, Idle Air Control valve problems, incorrect sensor input (coolant temp/throttle position), or a bad PCM. If you can duplicate the condition in park/neutral, that should make it easier to track down the cause.
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at email@example.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.
Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage -- visit Alex Steele at www.RealWorldAutomotive.com.