I have been restoring this 1996 Chevy K1500 V6 Vortec engine, 5 manual speed. Its shell has 237,000 with a replacement engine that has 64,000 miles. Almost everything has been replaced, from gas lines, brake lines, cat, clutch, etc. I was having many error codes regarding sensors, and It turned out that the computer was bad and was sending too much voltage to sensors, and I guess they were getting damaged. I replaced the computer and the dealer programmed it. Replaced basically every sensor, the spark plugs, wires, rotor/ distributor, coil and replaced the fuel regulator. I finished about three weeks ago and I thought everything was good, perhaps because I was only driving 10 minutes to work. Today I took her for a long drive on the highway and after 30 minutes, the engine started to hesitate, like there is no power (like it is running out of gas -but the tank was full). So I will park, turn the engine off, restart, and the truck is fine again for 10 minutes or so, then the hesitation would come back, turn truck off, turning right back (so it is not like I am letting it cool off, then the truck drives fine again! I never heard of a problem like this… and there are no engine error codes (yet)… One last thing, on the highway, the truck will no pass 55 MPH!
Your suggestions are greatly appreciated,