Its a 1991 3.9 L V6. Several gas tank fulls ago- I put in STP fuel injection concentrated cleaner, it helped allot, but now my truck is revving up to 2000 rpms wether I'm in park, or goin down the highway. Also, I took it on a 1600 mile road trip, soon after is when it started acting up. It was put on diagnostics but don't think anything was found- so could this have something to do with the fuel injectors? OR WHAT??? PLEASE HELP!!!

 

As far as I can think it would be a idle control motor or a vacuum leak. check all hoses and wires and if you cant find it. get a guage and unplug each hose and put the guage hose on that one and see if it changes. If you cant find it you might have the plenum gasket leak.

 

I once had a similar problem goin down the road and all of a sudden my rpms would start bouncing all around and sometimes it would eventully stop. But it sent a code for the EGR and I changed that but it didn't help, but what it turned out to be was the O2 sensor.

 

what is a tbs?

gutzy.

 

Sounds like you're referring to the throttle position sensor, they can do this to these trucks