'94 K1500 5.7 fuel problems
January 13th, 2012, 9:16 PM
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'94 K1500 5.7 fuel problems
I have a '94 Chevy k1500. It originally had a 4.3 v6. After the 4.6 wore out I built a 355 from 350 out of a '92 G30 van. I installed true duel exhaust with 40 series Flowmaster mufflers on each pipe. The cam is a 4x4 extreme cam from pro comp cams. It has .425 duration I believe. I really can’t remember exactly.
I ordered a prom for the vehicle from Chevrolet for the truck with stock 5.7 from '94.
The O2 sensor had to be replaced but other than that there were no issues for two years.
Now it has a problem with fuel.
When the truck is started it runs fine in open loop for a few minutes and then begins to surge. It cycles in and out of closed loop to open loop and the learn control bounces back and forth between enabled and disabled. If I hold the throttle at about 2K it bounces like it has a vacuum leak from 500 to 2000 rpm. If I try to drive it like this it stalls, sometimes backfires (out the exhaust), surges, and the transmission has a hard time picking what gear it wants. The throttle pedal has to be feathered to keep it running and it has to be double footed until it finally stops acting up and drives normal. It acts just like it warmed up but I have yet to find a connection with a distinct temperature changing the way it acts.
I have so far changed...
ECM, MAP sensor, TPS, EGR, IAC, ignition control, throttle body, injector connectors, fuel pump, fuel pump relay/ fuse, ECT sensor, plugs, plug wires, distributor cap, rotor, fuel filter, knock sensor... I think that’s all so far.
I have ohmed out all the wires from the fuel pump, pump relay, oil pressure sensor and back to the ecm from all of these.
I recently read about a gasket on the IAC I may have leaking. I will check that and repost.
Jeff
I am so tired of troubleshooting this to no avail. Anybody got any ideas?
I ordered a prom for the vehicle from Chevrolet for the truck with stock 5.7 from '94.
The O2 sensor had to be replaced but other than that there were no issues for two years.
Now it has a problem with fuel.
When the truck is started it runs fine in open loop for a few minutes and then begins to surge. It cycles in and out of closed loop to open loop and the learn control bounces back and forth between enabled and disabled. If I hold the throttle at about 2K it bounces like it has a vacuum leak from 500 to 2000 rpm. If I try to drive it like this it stalls, sometimes backfires (out the exhaust), surges, and the transmission has a hard time picking what gear it wants. The throttle pedal has to be feathered to keep it running and it has to be double footed until it finally stops acting up and drives normal. It acts just like it warmed up but I have yet to find a connection with a distinct temperature changing the way it acts.
I have so far changed...
ECM, MAP sensor, TPS, EGR, IAC, ignition control, throttle body, injector connectors, fuel pump, fuel pump relay/ fuse, ECT sensor, plugs, plug wires, distributor cap, rotor, fuel filter, knock sensor... I think that’s all so far.
I have ohmed out all the wires from the fuel pump, pump relay, oil pressure sensor and back to the ecm from all of these.
I recently read about a gasket on the IAC I may have leaking. I will check that and repost.
Jeff
I am so tired of troubleshooting this to no avail. Anybody got any ideas?
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