Flickering lights, rough idle, bogging down

[BlakeOfDoom]

OK, so when I start my 91 navajo the whole truck idles really high and the voltmeter on the dash goes crazy,. There is a brand new alternator in the truck but the needle still swings erratically at times. The headlights also flicker as well, not dim, just bright and brighter.

The truck also has a tendency to die when rolling to a stop. I have replaced the IAC valve but the problem keps persisting. One morning the truck did not die at all until I put it in reverse, then it just died out. When I start the truck the idle is erratic and sometimes the truck will die just idling.

The last problem is when I'm on the streets or highway and the truck loses rpm all of a sudden then jumps back up. I have replaced the fuel filter but that does not seem to be the problem... Any ideas?

 

[MrShorty]

Things I would probably look at:

1) pull codes, even if CEL is not on, just to see if the PCM is seeing something
2) check fuel pressure
3) check for vacuum leaks

 

[jungleryan00]

Check the throttle position sensor.