Bad idle GMC s15 4.3 v6 question.

[BLACK6PACK]

My parents just gave me a mid to early 90s GMC S15 or whatever they're called with a 4.3 v6. It only has 60k miles on it and is in really good shape. We've changed the plugs, wires, cap, and rotor, but the thing idles poorly and will die. Most of the time its ok, but with the ac on it will die every time at idle when it is in gear. Any idea what could be causing this? Truck runs fine otherwise. It will die without the ac on at idle, but its somewhat rare, with the ac on it does it every time. It probably needs a new fuel filter, but other than the basics I'm stumped. This thing is a TBI, with I think two injectors, haven't really looked.

 

[NCTyphoon]

Try cleaning the Idle Air Control & throttle body

 

[darkred87T]

Vacume leak?

 

[dgoodhue]

The spider injectors is a common problem with those motors.

 

[klrv6]

If its a W motor.

The spider injectors is a common problem with those motors.

If the 7th letter in the VIN is a W, then I would look into the injectors. I had a 95 HO 4.3 W motor in my S10. It ran awesome when the injectors or EGR wasn't all screwed up. You can search online for ways to clean the EGR valve, a common problem on either TBI or MPFI motors. Check your fuel pressure and clean the idle air control valve, just to be safe. When was the last time it had fresh gas in it?

 

[BLACK6PACK]

Good point about the gas. The parents rarely drove the thing. I'm not sure if I filled it up before driving 110 miles to my house or if it was already full.

Thanks for the input guys! I'll check everything mentioned in this thread.

 

[klrv6]

The W engines HATE bad/old gas.

I let my truck sit on jack stands for almost a year once. Man, that thing was pissed when I drove it for the first time. I just bypassed the fuel pump and drained the entire tank. The old gas ran in the mower with 93 going back in the truck.

 

[Little6pack]

my 4.3 s10 doesn't like to even start unless it is above 45 degrees. doesn't do me any good having 4x4 in winter when she won't turn over. Just cranks & cranks.

 

[BLACK6PACK]

Luckily I don't have to worry too much about that. We did have one day about a month ago that got down into the 40s.

 

[karst#9]

Most likely the egr valve. My wifes 95 has had 3 egr valves already Also check the fuel pressure to see if it holds. If it leaks off the fuel regulator is probally bad. GM or some parts stores will try to sell you the whole spider injector assy. because they say you cant just buy the regulator, but you can go to a parts store with the HELP rack and you can get the regulator for about $45, or they can order it. Saved me alot of money

 

[klrv6]

You can clean the EGR.

Just use throttle body cleaner and a hex driver to work the pintle up and down, flushing with cleaner every once in a while.

 

[SFITurbo]

Early 90's (late 89's) don't idle smooth no matter what. 92 and up?? have internal balance shaft for cam that was supposed to help with rough idle.Check timing and insure the brown wire under passenger dash is still connected. Check for codes stored and reset.