I just bought a 1987 s10 Blazer 2 door with a 2.8 out of a 1992 s10. When your stopped the engine with sometimes rev up real high and then when your driving it will do the same thing. Also it hesitates really bad when you step on the gas. Any help would be great.

 

When I say It revs up high thats without putting your foot on the gas

 

sounds to me your Throttle position switch is going bad. but I could be wrong, I dont know much on the 2.8's.

 

Start with the easy stuff and check the vacuum lines for leaks. Use carb cleaner spray on their connections, if the revs go up a little you found a leak. Sometimes you can hear them hissing if its bad enough. Check condition of tune-up. Any obvious leaks or unhooked connections.

 

I'll check the lines I was also thinking the TBI might be bad the guy I bought it from has it kiinda rigged in there. Could the fuel filter be bad?