1995 GMC C1500 idle air control

1995 GMC C1500
131,000 MILES • V8 • 4WD • AUTOMATIC
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SISNEYFAMILY
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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.
Jun 2, 2008 at 12:30 PM
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RASMATAZ
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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
Jun 2, 2008 at 1:25 PM