S10 high idle

[XFIREZ28]

1991 s10 2.8fi had a a sluggish start-up.. like rotor or damp cap,so i replaced. now idles 1000 or more rpm. runs good.. any help thanks z

[RahX]

check for vacuum leaks, sounds like a small leak. look for any obvious cracking/splitting/outright breakage of vacuum lines. pinch off lines coming from the manifold and see if it changes anything. if it does trace that line and pinch it off until it doesnt affect the idle and check between the last pinch that affected the idle and the pinch that didnt.

[XFIREZ28]

Originally Posted by RahX

check for vacuum leaks, sounds like a small leak. look for any obvious cracking/splitting/outright breakage of vacuum lines. pinch off lines coming from the manifold and see if it changes anything. if it does trace that line and pinch it off until it doesnt affect the idle and check between the last pinch that affected the idle and the pinch that didnt.

thanks, i will look again, if not vac. any other ideas

[jsgold]

Might try removing the IAC (Idle Air control) valve, cleaning it, and see what happens. be sure to unhook your battery FIRST and then remove the IAC. Let it runs for awhile after restart to learn idle.

[RahX]

im pretty sure its a throttle body motor. in which case the gaskets for the tb are fairly prone to leakage. not a big deal, 3 bolts and some ingenuity and you can slip one in without too much trouble. also unhook the brake booster vacuum line and put your thumb over that, sometimes the boosters leak and ive had 2 that seeped all the time, not common but possible.

[XFIREZ28]

Originally Posted by RahX

im pretty sure its a throttle body motor. in which case the gaskets for the tb are fairly prone to leakage. not a big deal, 3 bolts and some ingenuity and you can slip one in without too much trouble. also unhook the brake booster vacuum line and put your thumb over that, sometimes the boosters leak and ive had 2 that seeped all the time, not common but possible.

thanks RahX & jsgold..... u no measure twice cut once. so i went back double check... i found the bottom vac hose at bottom on back throttle body i didnt see it with all wires and stuff... thanks guys. 289000 and still climbing again , just a lil scare on my roll!!!

[RahX]

good to hear

[markshuman]

Originally Posted by XFIREZ28

1991 s10 2.8fi had a a sluggish start-up.. like rotor or damp cap,so i replaced. now idles 1000 or more rpm. runs good.. any help thanks z

I have a 98 4.3 that had simillar symptoms. It would hang on to the rpm's when I was coming to a stop, then slowly idle down to 500 rpm's ( normal) I sprayed the hell out of the throttle body & butterfly valve with a carb cleaner. That took care of my high idling. Also check your idle set screw. It may be adjusted too far in. I also changed out the plugs, dist. cap & rotor, and the fuel filter. All are easy to do ( 'cept the plugs) & made it run tons smoother ( kinda something you sense more than feel ). I have also experienced a difficulty in starting. It fires right up first time of the day, then I have to crank it a bit to start anytime after that. I've learned that these (4.3 vortec engines ) have a bad problem with carbon buildup, so I've been using Seafoam injector cleaner in my last 3 tankfuls. So far it's been firing right up all the time. Luck