Ok, so i have a few post floating around, trying to figure why my 2004 Blazer runs like crap. It tends to have a rougher idle and I basically went through all the normal culprits, with the exception of replacing the IAC (also, no EGR so that is out). I cleaned it, but did not replace the IAC. I still have some issue with the truck and idle/drivability. Seems like it is restriced somehow and also when I let off the gas, it feels like there is an exhaust brake on the truck (jake brake).

I also thought it could be a vacuum leak, but cannot seem to locate anyhthing on the topside of the motor or intake. With everything off the throttle body, I had my wife start the truck and had the IAC unplugged. The truck revved to 5000RPM before she shut it off. Is this normal? is the IAC bad? need a little help with this.

Additionally, I was thinking that the cam position sensor was on its way out. Maybe, thoughts?

thanks

 

Have you checked the fuel pressure and ran a leakdown test on the fuel system?

 

What you created by bypassing the IAC (disconnecting everything) was to create a huge vacuum leak! This will result in unrestrained RPMs! The IAC is connected via vacuum line to the main intake at the intake manifold located left front of center of the TBI-other posters have had this same problem just recently,do a search of this site! You will find your problem! Let us know!