Questions and Answers

Chevy S-10 Has No Power Q. I have a 1994 Chevy S-10 with a problem even the shops can't figure out. I hope you can help. My engine has no power between 2,500 an 3,000 rpm. The problem is more noticeable when the weather is warm. It developed around 110,000 miles. Before and after that range it runs like when new. No trouble codes on computer.

My first guess was TPS. I tested it, checked good. Smooth through entire range. but eventually installed a new one any ways which also tests good. Replaced EGR, IS sensor, MAP sensor, O2, fuel pump (which also tests 42 and 47 psi while driving), fuel pressure regulator, all vacuum lines, plugs and wires, coils, ignition control, crank sensor, computer minus chip.

I took the truck to Pro Tune and had them run it on the analyzer, mechanic said all readings were spot on. Engine vacuum readings are high and steady. I replaced the head gasket due to coolant leak at back of engine. Compression good on all cylinders.

Any advice will be greatly appreciated, I love this truck, had it since it was new and want to keep it but the problem is driving me crazy.

• 1994 Chevy S-10
• 2.2 liter
• 5 speed
• 135,000 miles

Thanks in advance,
Howard

A. You say you replaced the EGR. Did you use a GM valve? This is the rpm range that the EGR would be opening and an incorrect valve could open too much and dilute the air/fuel mixture. If I'm not mistaken, this is a vacuum operated valve. Try taking a golf tee and put it in the hose for the EGR valve and drive it. If you are describing a sag, bogging down type of thing, it sounds like a fuel supply problem or a pressure drop.