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Ok, so I bought this truck as cheap transportation with 250,000 miles. The truck always missed randomly. I found that the upstream O2 sensor has the wires ripped off. I found a wiring diagram and reconnected it. It was still missing. Recently I replaced the distributor cap and rotor, at the same time, I decided to remove and clean the throttle body as it was black in the intakes.
I cleaned it up and re-installed it and the sensors. Now, it misses worse than before. I can't hold a steady speed without it bucking. I have checked the plugs, they are all firing. Compression seems ok for an old truck. The pedal seems to have a dead spot in it until I get to a particular spot, then all cylinders kick in until it gets up to speed then the mis comes back until I depress the pedal more. I replaced the TPS, not difference. Here's the strange thing, if I disconnect the MAP sensor, it actually runs a little better but won't gold an idle. If I disconnect the MAP and IAC again, it does a little better but you can smell the gas, so it seems to be running really rich. Also, when the truck gets to running speed, the oil pressure gauge drops to zero periodically and the oil light comes on until I press the gas pedal a little.
I have checked for and plugged all vacuum leaks. I have cleaned all electronic connectors, cleaned the sensors with MAP cleaner, re-checked, cleaned and re-gapped the plugs. I am really at a loss and I really need this fixed. Can anyone please shed light on this. Also, I have replaced the coolant sensor because it was the only code in the computer. I replaced it, but the check engine light still hasn't gone out and still the only code on the truck is for the coolant sensor. Also, the truck seems to run hot even though I also replaced the thermostat. It runs a little over 200, is that too hot?
Anyway, I know I gave a bunch of info, but I figured you should have all the facts.
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