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1999 GMC Yukon Question: 99 Yukon desn't want to decelerate most of time

 

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John Baxter, Fresno, CA, January 07, 2012, 20:15
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Have 99 Yukon 2wd 5.7 135,000 since new and most of time engine will not slow until I apply brakes. Idles correct, no service light or code. Years ago dealership replaced TPS and worked a couple days and returned. This also can happen if I pull say the MAF or other sensor wire, run then reconnect, it may decelerate properly for a day then back again. It comes and goes on its own. In a parking lot, engine will run 1500 or more RPM until I apply brakes then it idles properly. Will decelerate all the time by putting in a lower gear with higher RPMS - like vacuum has some affect. Driving it will take 3 blocks in D3 to slow from 40 MPH to maybe 30. Will decelerate when driving, if I shift to neutral and back to drive. Also has a 3 second lag period from releasing throttle to engine slowing.(maybe normal?)Thinking MAF or MAP?

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