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Timing Problem
Hello,
I have an 88 Chevy 5.7 350 c1500 1/2 ton rear wheel drive truck with electronic fuel injection and a Throttle body injection. I have been working on restoring its youth and have run into a couple of problems. One main problem that I have is the timing. I disconnect the Electronic Spark Control wire to bypass the module, (to set initial timing) and time my truck to 0 degrees, but as soon as I plug back the ESC module wire back in, the timing, checked with my timing gun, goes to about 20-30 degrees before (counterclockwise on my vibration damper) 0 degrees. IS THIS NORMAL? or should it remain the same; at 0 degrees? (this is all done at idle speed in park) The strange thing is that the truck runs smooth for most of the time, only during hard acceleration I hear a fast tapping or clicking, but I'm not sure if it is preignition or if it is valve tarin or some other noise. My question is can any of the sensors relay bad information to the ECM and cause it to change the timing incorrectly? I have been assuming yes, and i have changed several sensors (speed sensor, throttle position sensor, EGR Valve and solenoid, the ESC module itself, idle air control valve, distributor, spark plugs and wires, coil, coolant temperature sensor, and even the computer itself) ( I have also changed the timing chain and gears a long time ago) I have not changed the coolant temperature SWITCH, the MAP sensor and the knock sensor, but I do not want to change these sensors without making sure they are faulty. How can I test these items. Before I changed the distributor (which was the first thing I did) the car would misfire like crazy, and my guess is that it could have damaged the knock sensor causing it to relay bad information; is this possible? There is no carbon in the engine as it has been thoroughly cleaned. I understand there are a lot of questions here, but I am sure somebody knows the answer to some of them....
Thank you,
Matthew
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