1995 GMC C1500 idle air control

SISNEYFAMILY

MEMBER
1995 GMC C1500
V8
4WD
AUTOMATIC
131,000 MILES

My 95 gmc truck will not start sometimes. Espically if it is or has rained. I put a code reader on it. It said coolant temp switch and idle air control valve. I put the coolant switch on and it ran for a while. I replaced the iac and now it is back to not starting. I cannot reset the code reader till it starts again of course, I am at a loss. Thank you.

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

My 95 gmc truck will not start sometimes

Other than the coolant temperature sensor/IACV -check the closed/WOT throttle voltages. Did you cleaned the IACV passages-also the CTS hot and cold resistances-

If the engine's condition is in tip top shape-do below to determine if its fuel or spark problem that's if its cranking over and refuses to start

Get a carb cleaner and spray into the carb or the throttle body on an EFI. Did it start and die? If not disconnect a sparkplug wire or 2 and ground it to the engine -have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel problem, check the fuel pressure to rule out the fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light.

If both fuel and spark is present-check the valve and ignition timing, this will lead you to problems with compression and valves opening and closing at the wrong time