I know I have posted this before, but I am now getting to the point that Im ready to place a bomb in the car, just kidding. I have had this problem since I bought the vehicle in Sept. of 2000. It runs great when its cold. When the engine reaches normal operating temp. is when the problem rears its ugly head. The car becomes sluggish, sometimes when I first press the accelarator it hesitates like its not getting fuel then it takes off, also, I dont know if this is related, but I can physically hear my fuel pump running even with a half a tank of gas, when the car shuts off a high pitch whine can be heard in the rear near the fuel tank. I have checked the fuel pressure, it read 37 psi at idle. I just did a complete tune-up, what a bitch, replaced wires, plugs, rotor and cap. I pulled the ecm codes and it read normal (12). I love these cars, and have always wanted one, finally my wife broke down and let me buy one. It is a 1988 with the 5.7, with 73,000 miles. If anyone can help me I would be eternally greatful. I figured I could turn to my fellow GTA brothers.

Thanks
Robert Hill

 

I had a similar issue like yours. When I bought my Z, it would run great until it got up to operating temp, then it ran like c***. Then it got to the point that if it got hot, it would die. After going through the same things you did, I stated looking else where. I found that I was missing a heat sheild that goes over the muffler, to block the heat from the gas tank. I put a new one on and it helped a little bit but not much. I ended up replacing the fuel pump and have never had that problem again. The pump might be the problem and it might not. Hope this gives you some direction to go. Also, with as many miles as you've got, a new pump wouldn't be such a bad idea.

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'91 Z-28 5.7, SLP 1 3/4 headers, 4 inch Mufflex/Flowmaster cat back, gutted cats, Edelbrock intake, 8.5mm Jacob wires, MSD Blaster coil, S&W subframe setup, Jacob Pro Street Ignition, complete Kenwood system.

 

Sounds like when you get driving down the road, the pump can't keep up.

I would check fuel pressure while driving.

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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

R.I.P. #3
My favorite quote about D.E. "He can see air"