Why does it rough idling on startup?

Asked by Mar 03, 2017 at 01:56 PM about the 1995 GMC Sierra 1500 C1500 SLE Extended Cab Stepside SB

Question type: Maintenance & Repair

Weather its  cold or warm on startup it idles rough then rpm goes up to 1500
and smoothes out and runs great, idles good after that.

2 Answers


I would take out the Idle Air Control Valve, then take the throttle body off and clean the throttle body and the port for the IAC out good. You may even want to replace it unless they can test it at the auto parts store. Same with the EGR Valve, take it off and clean the carbon off and make sure it works. Also just snug up the intake manifold bolts.

Try checking your timing and make sure the distributor is tight

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