I have a 91 4.3 4x4. I just recently changed the plugs and wires and now the vehicle just wont idle. It drives fine but if I'm not giving it gas then it will cut out.

 

Have you checked the EGR valve? Usually it builds up carbon and it stops it up, causing the bad idle. Had to put a screen filter over mine. Works great!

 

did you check your iac valve ? (idle air control ) its located on your tbi.

 

From your description, it would seem that the idle quality was reduced by the tune up. Is this the case?

 

Yes that's correct. It idled fine until the tune-up. Whatever the problem is its most likely my fault.

 

by any chance did you use delco parts?

 

No I just did plugs, wires, oil, and filters. Parts master and wix were the brands I believe.

 

that might be your problem these trucks run bad with any other markets i learned my lesson the hard way but yea i say go with ac delco

 

After getting it in the garage I see now that it blows what looks like water and oil maybe out of the tail pipe.

 

I had the same problem with mine - same year and model. Changed the wires, plugs, coil - nothing. Removed the throttle body and cleaned and replaced all the gaskets and replaced the fuel pressure regulator ($) - nothing. Pulled the fuel filter off under the frame on the driver's side and replaced it - success!... for about 20 seconds.

I'm not saying the "tune-up" had anything to do with it, so maybe it was just coincidence, but I ended up having to remove the fuel tank and replaced the fuel pump. The hose (like an inch-and-a-half long) was spongy and cracked and was not allowing ample fuel pressure to the engine. After I replaced the pump, hose, and internal tank filter, it runs like a champ. There is one more thing I'd recommend, though - and that's checking the injectors. I still have a leaky one and it sometimes dies when I idle down quickly. It's a $70 fix and would take about 5 minutes - and that's why it hasn't gotten done yet. Good luck!