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Question

I don't get the P0305 code when I start up and run, but after the truck has warmed up and been driven for a while, then shut off for a while, then started up again, that's when the CE light flashed. It runs rough during this time, but not after the initial early start. It seems like something relating to engine temp or an electrical switch/sensor not acting properly or resetting after it warms up and is restarted. Any tips or where to look would help. I had lean codes recently (P0171 and P0174), but fixed that problem with new vacuum line connector. But the P0305 persists.

Thanks!

Answer 1

Hopefully this is not a mechanical condition, , when the engine is code the valves seals better, but once the engine warms up the valve expand due to heat this is one of the reason for a misfire condition when the engine is warmed up, They you can find this is either with a ignition analyzer or running compression test, (not a compression test, compression test , it would miss its mark) Also be aware when it comes to a Ford vehicle the number 5 or the number 3 cylinder when it misfires it usually a EGR related misfire condition, the reason lets say the EGR is slightly open More EGR gas enter the number 5 cylinder than any other cylinder. You can disable the EGR by removing its vacuum hose and retest.

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