My 2004 Blazer has had a significant amount of work done to it and yet it is still running rough @ idle. Now however I have a very DANGEROUS SITUATION.

I thought that it could possibly have been my IAC that was causing the rough idle, so I took it off and cleaned it to get the carbon off and such. The problem I am having now, I was driving the truck and and after taking my foot off the accelerator, the truck actually started to accelerate!! I thought that the cable could be stuck, so I revved the engine and it still wanted to drive.

I then came to a stop....put the truck in reverse and took my foot off the brake. Truck began to go backwards and then RPM's went up and truck started to move faster.

This is obviously unsafe and I NEED HELP!!

IAC bad maybe??

Please, I cannot let this safety issue go to long.

thanks

 

what does your truck idle at?

 

Recheck any and all connections on the motor and check all of your throttle cables and make sure they aren't sticking or obstructed in any way. Another thing you can try is to disconnect your battery for a bit and reset the pcm/ecu so they can re learn without the carbon build up. I had to do this when I cleaned my throttle body so it wouldn't rev so high. Give that a try and let us know how it turns out. And hopefully someone smarter than me will come along and chime in as well!!

 

Thanks for the help....I will try these remedies and let you know. I am starting to think the rough idle is a vacuum thing, as I just noticed that the HVAC is not diverting properly and I know this is controlled by the vacuum lines. I had the problem before and found the line was disconnected because the transfer case actuator was stuck. I fixed it and was fine, but now doing it again and with everything the truck has had done part wise it has got to be somewhat vacuum related.

The truck typically idles somewhere around 600-700 RPM's.

Also, could a vacuum issue have someimpact on the shift points and such? occasionally it seems to drag or have prolonged shifts.

Thanks for the help. I am sure I am going to be here often as things continue to arise with this truck.

Thanks,

Carl

 

Thats kind of what i was thinking was a vacuum leak. But i also say disconnect the battery like Rex said.

 

Make sure you check your floor mats too! I had my pedal get stuck on the edge of my floor mat one, freaked me out, wouldnt stop so I threw 'er in neutral then killed the ignition quicky.

 

im guessin an intake gasket leak.... i had the same problems with my Chrysler LHS its just sucking air

 

I had a Lumina that did something similar & it was a blown fuse that controlled the IAC. I have no idea if the Blazer is similar or not, just a thought. What blew the fuse was a short in the A/C wiring. Because when you turn on the A/C the IAC has to compensate for the load at idle. What I had was a high idle of about 1200 rpms it wouldn't come down, until I replaced the fuse.
I cleaned the IAC. Nothing. Finally I called a friend that was the computer mechanic for the City, IE all the Police & Fire vehicles. He told me what it was & where to find the fuse etc.

 

I have to agree with the vacuum leak issue,check the seal at the main vacuum port to the left front of the TBI,also make sure it is properly seated and/or not cracked. I have found it fairly difficult to kink or bind the accelerator cables on these motors as once they are removed as a pair they can be safely be turned back to the cowl while service is being done. A lot of other good suggestions here as well!

 

So i unplugged the battery and it seems the truck is running well. Still has a rough idle, but seems to have better pickup and the "self driving" is not there. The truck does still have mo.ents of funny shifting, but i still think that a vacuum leak is the culprit. STEP66....do you have photos of the vacuum port you speak of? Also, i assume vacuum because my HVAC is not diverting properly ...so.

I will keep you posted.

Thanks!