1986 GMC S15 Sierra Classic 6 Cyl 2.8L
Does this model have a( throttle position censor) ?
Automatic after starting it up in park the idle speeds up and slows down quickly back and forth.I was told this could be the cause. When shifting out of park into drive it starts to race immediately until locked in gear then normal. Any suggestions would be appreciated. Just started this. Thank You.
You have to rule out a vacuum leak before you start replacing stuff. The TPS can be checked with a simple voltmeter. Just google TPS check. Look for a vacuum leak. The gasket under the throttle body can leak vacuum. The power brake booster can leak vacuum. Any vacuum hose on the engine that carries vacuum can crack / split and leak vacuum. make sure that you do not have a way overdue and forgotten clogged up fuel filter with a gazillion miles on it. That could starve the engine for fuel and cause your erratic idle.