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Username Post: 89 5.7 tbi running rich
J-dawg 46 
Posts: 7

Age: 61
Loc: Swift Current, Sk
Reg: 10-31-22
12-14-22 11:32 AM - Post#2851251    

I am building a 46 chevy truck on an S10 frame with a 1989 chevy 5.7 tbi engine with the GM#1227747 ECM. The engine seems to be running rich as the plugs are black and the exhaust is black, it idles for a bit and the idle drops and sometimes comes back, but usually stalls. When driving, it backfires out of the exhaust and doesn’t accelerate properly. If I unplug the MAP sensor it idles nice and revs up nicely. No codes are showing up. Fuel pressure is a steady 11-12 psi. Vacuum is steady at about 17-18 inches (elevation is about 2700 feet). Compression is 150-170 on all cylinders. I have removed and blocked the egr from the engine so I am not using the egr wire in the harness. I have replaced the cts, 02 sensor, MAP sensor, IAC valve, spark plugs and wires, distributor cap and rotor and pickup module. Then we tried swapping the computer, coil, distributor, and throttle body from a good running vehicle and it still didn’t help. I have the ground wires to the engine block from the harness, the body to the frame, engine to the frame. Any help would be greatly appreciated.
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