Dear engine experts.
I have a problem with the idle on my 2.5Lfuel injected 1988 S10 manual trans. I have replaced the idle control valve, the mapp sensor, checked for vacuum leaks. I have replaced the intake manifold gasket the erg valve gasket and the throttle body gasket, I still can't get the idle speed down it's about 1800, and replacing the gaskets did not change the idle speed. I sprayed water and carb cleaner all over the place looking for leaks. I have had all the hoses off and examined them, I have plugged hoses one at a time. The computer says Idle air control is bad, I replaced it shut. I let it close and unplugged it and idle speed did not change. There is light showing around the butterfly of the throttle body but it appears closed I have not pulled the plug and tried to adjust it more closed.
Help me please, I am at witts end and I can't afford to get a dealer to fix it. The computer controls the mixture ok but it will not pass emissions with the idle speed this fast. If I had money I wouldn't be driving this rust bucket. Otherwise the truck runs good and doesn't burn oil and it's my only vehicle.
John