Hello, I have a 96 Chevy Blazer, 4.3L V6. Sometimes after start-up it will rev up to 2500 rpms. Recently, it has shut-off after this if you don't put it into gear right away. Any ideas?

 

try start with cleaning your TB and IAC valve, and while your at that might as well clean the egr too. not saying thats what it is, but all those things can contribute to a bad idle. make sure you do the passage inside the TB for the IAC valve.

 

the TB valve is located in the throttle box correct? if so, then where would this be at?

 

nevermind i located the IAC vaue. Ill clean it tomorrow when i pick up the cleaner spray. Ill let you know what happens.

 

This didnt fix it. But thanks for the input. Anymore ideas??

 

It could possibly be a vacuum leak. How does the truck run? does it idle rough or seem down on power? Check over all the vacuum lines and check to see if any are dry rotted or cracked. How are the LIM gaskets? If they are leaking coolant at all they could also not be sealing around the intake runners creating a vac leak. If you cant see anything obvious try the carb cleaner trick and spray down any suspect areas while the engine is idling, if the idle jumps you found your vac leak.

 

^ yup, try that. hopefully you still have some carb cleaner left.