Questions and Answers

GMC S-15 Jimmy Loses Power On Hills Q. Hi Vince, I truly hope you can help me. This is so aggravating and worrisome for me. I have a 1993 GMC S-15 Jimmy with a 4.3 liter engine VIN code "W", automatic transmission, 2WD with about 180,000 miles. It has all the basics, P/S, A/C and fuel injected. Here is my main problem, I notice it mainly at about 65 to 70 mph if I encounter an incline.

The engine begins to hesitate and stumble, I am usually in cruise control when this happens. It will normally drop into passing gear because of the loss of speed. Once it shifts down the hesitation goes away until it shifts out of passing gear then if I'm still on the hill it will frequently do it again. It seems to get worse with the length of the trip.

Recently the Check Engine Light (CEL) came on and the truck ran really bad until I got to my destination. After I shut it off the, light was out and it seemed to run okay. I jumpered the terminals to get the codes and it was the EGR system code so I pulled it and cleaned it out. But it didn't help the stumbling so I replaced the fuel filter then the coil and finally the O2 sensor but I still have the problem. PLEASE HELP!

Thanks,
Mike

A. How about some basics? What is the state of the spark plugs and ignition wires? It could also be transmission related. Have you had fuel pressure checked? Possibly the fuel pump is on it's way out.