Truck is running funny

Ok, a few weeks ago my 90 Chevy 1500 w/350 started running weird. It will start ideling high then low, high then low...... And smells very much like fire crackers. WTF?!? Its only noticeable when you're are a stop light or you let off the gas to come to a stop. It doesn't seem to do it when you're driving down the road. What can the problem be???

Thanks in advance guys.

do you have a catalitic converter on your truck if so it might be plugged

if you can talk to a chevy mechanic that has worked for a chevy dealer for awhile. when i worked at a chevy dealership back in 95 my dads truck(a 92 with a 350) had that same problem with only 35,000 miles on it, but i can't remember for the life of me what the problem ended up being, but i remember a mechanic telling me it was a common problem.

Ok thanks guys. Anyone else have a comment about this problem???

bump.

Originally posted by DrgnDor

And smells very much like fire crackers.

Haha, that's funny! Could be trash in the gas or clogged injectors...my truck was doing pretty much what you mentioned awhile back, and it took a couple tanks of gas with a couple cheap bottles of fuel-injector cleaner to clear it up........

Hey man i had the same problem. What i did was i had to replace the ignition control module which is under the cap and rotor where your plug wires run into. Its a little black u shaped thing with two plugs goin to it. That was bad and a wire was grounding out to the body of the distributor. I dont know if thats whats happening to yours but its something you can check.

tps sensor or convertor