1990 Chevy Pick-up - Puzzle To Be Solved


#1

My 1990 shortbed Chevy, 6 cylinder engine, 133,000 miles, has suddenly developed a serious idle/choke problem. It has electronic ignition so no carberator to adjust. Whne I start it up, it wants to die immediately unless I keep my foot on the accelerator. When I put it in drive, it spits and sputters like it isn’t getting enough gas and then it will smooth out once I get it going down the road. It runs perfectly crusing down the road but the idle lunges up and down when it’s stopped (in drive) or put in park. And forget about going in reverse. It will just die continuously unless you can reverse with your foot in the accelerator. I’ve had it tuned up and it’s been looked at by two very experienced mechanics. One of the mechanics said he has the same truck and there was a factory bulletin about some type of computer chip that costs about $90 but he says he changed the chip in his and it didn’t fix it. He’s been messing with it for over a year and it’s still doing the same thing, still running, no better, no worse. One of the shops ran the computer test on the truck and it doesn’t show any discernible problems. Is anyone familiar with this problem? It’s driving me crazy!


#2

Engine surging, otherwise referred to as ‘loping’ can be caused by a number of things.

Here are a few:
*Vacuum leaks (check all hoses and all air intakes)
*Possible leaking EGR valve or plugged PCV valve
*Clogged air filter
*Leaking head gasket
*Worn timing chain
*Worn camshaft lobes
*Burned valves
*Faulty ignition system
*clogged or dirty injectors or perhaps a faulty emissions system

Any stalling can be attributed to a faulty IAC valve, maybe a bad fuel regulator or partially plugged fuel filter


#3

I have a 91 chevy pu.
It could be all of the above. But check the throttle body wiring on the carburetor. I had a short in mine and it blew a fuse and because I was road Kill (stuck along away from home) it cost me plenty.
Just the towing cost $250.00.
Boy I miss my Dodge.