So i have a wierd problem and not to sure where to look first, im pretty sure its a sensor somewhere.
So my truck idles high in park. Ok not a problem adjust the idle by adjusting the timing a little bit. Ok so it fixes the problem for a little bit then it goes back to the way it was before.
while the truck is in drive, only after it warms up and has been drivin a lttle bit, when i come to a stop the RPMs drop real low to about 300-500 then jumps back up to like 1000-1100. and will keep droppin and raising. and this is getting worse, the truck is starting to buck a little when im stoppedand the RPMs jump up. and i know its annoyin the hell out of the people around me because its bothering the **** out of me. also the volt gauge will sometimes drop in unison with the raising and lowering RPMs.
the RPMs and volt gauge only drops and raises in drive.

So who can tell where to look at first? Im very positive its a sensor somewhere but dont know where to start first.

 

The voltage just sounds like a factor of the truck dropping in rpms and the alt. slows down as well

I would start by taking your IAC (Idle air control) sensor off and cleaning it thourougly

 

thats where i was thinking to start but wasnt sure

 

Get some electrical parts cleaner and clean all your sensor pigtails as well, it cant hurt.

Also check all of your vaccum lines for cracks or dry-rot

 

all the vacuum lines have been replaced so they are good or at least they should be

 

Disconnect your IAC when the engine is idling and see if the engine will die. If the engine still runs-you have a vacuum leak in the intake manifold.

 

i would try but its absolutely POURING rain here

 

so i actually just replaced my IAC and it helped the problem but it is still there

 

Is your throttle plate on the 5.0 HO intake completely closed when the truck is idling?

 

You mean the blade of the throttle body?

 

check your tps it may have a dead spot at idle . put a vacuum guage on it your looking for a stable needle at idle. did you do anything before this started happening i would check first

 

No i did not it just happened but its all working fine now though I went back and checked the new iac over again and it wasn't plugged in all the way so it wasn't gettin good contact. But now that its plugged in the problem is gone

 

i was thinkning it wasnt coming out of warm up. but guess you go it

 

I spoke to soon, the problem has not gone away but it is severely reduced and only sporadic, and I checked the plug again to see if it came undone or something and it hasnt.

I'm thinking vacuum leak now what do Yall think

 

fuel milage crappy? check coolant temp sensor. spray around intake manifold with carb cleaner sometimes you can find it