2000 4x2 slt 3.9. I'm getting cel codes 300 301 303 and 305. Have replaced ign wires, plugs and rotor. Seems to occur just when the truck reaches normal operating temperature. Could that be an out of spec oxy sensor?
Art

 

Sounds like your spark plug cables are off...

 

I agree with Varsis



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Plug wires are correct. The cel only comes on during highway driving at constant speed after being fully warmed up. It must be a problem which occurs after the computer switches from open loop to closed loop. That is why I thought it could be the O2 sensor.
Art

 

At long last. After replacing plugs, wires, rotor, cap and crank position sensor with no improvement, they pulled the intake manifold and replaced the gaskets. It ran 3 days with no recurrence, then the light again. P0300, P0301, P0303 and P0305. Found the vacuum line to the cruise control disconnected. Rerouted the line so it wouldn't pull out again and reconnected it. Reset the computer. Been ok for over a week now. Was the manifold gasket. The mechanic used what he called a smoke test on the manifold and leaks showed up.
Art