91 Chevy K 1500 350 idle problem

[amac209]

you might want to get a competent shop to diagnose this. they have equipment to test the iac, might also be the ect(engine coolant temp sensor), tps(throttle position sensor) or the fuel regulator. or an O2 sensor. throwing parts at the problem gets expensive. for about an hour of diagnostic time a good mechanic will be able to check all these with a good scan tool and fuel pressure gage

[jay hullett]

if occures on first start and runs rough then smoothes out unhook egr valve and see if runs better gm had problems with egr solenoids opening egr on start up also ck fuel pressure need at least 9psi min 13 max also if ck engine lite on ck codes first, on anything non obd2 if a scanner not on hand go to advance or autozone and let them ck codes or in diag conector under dash cross terminals a and b with key on engine off and count ck engine lite flashes 12 is normal lite will flash long pulse first # and faster second #

[i8uiky]

kind of a long shot... disconect and plug vacuum to brake booster start your truck apply and release the break maby even drive slowley in your driveway. if it runs ok you have a vacuum leak in the booster



ps do you have any way to get service engin codes to us and remember engin codes only point you in the direction of the problem

[toivo]

unlpug your vacuum line to your charcoal cannister and block it off and see if your hesitation goes away. also when it is cold uplug your temp coolant sensor and see if it starts up and idles good. toivo

[BobM46128]

You also might want to try setting your idle speed. I know, I know the 'puter handles this. But on throttle body engines the TBI has a set screw that sets the BEGINNING idle. Then the IAC takes it from there. If your set screw has worn down too far, then the IAC has to move too far, too fast causing the engine to die.
I know that I am not calling this procedure by it's right name, but here is how you perform it: Let the engine warm up and then pull the vacuum line off the brake booster, causing an air leak. This will make the engine speed up with the added air and the IAC will slam shut. Turn the engine off. Disconnect the lead to the IAC and plug the vacuum hose back in. Restart the engine and adjust the idle screw. Then shut down the engine and plug the IAC back in.
It's worth a try if everything else fails.