I have a 1999 F-150 4x4 with 93000 miles and a 4.2l v6. I started noticing a decrease in power, rough idle and engine hesitation at 30-40mph. Also, fuel mileage has decreased considerably. I checked it with a Snap-On diagnostic scanner and found the ignition timing to be 22 degrees advanced at an idle. Upon acceleration, the timing went negative when I reached 55mph. This can't be correct. I took the truck to a dealership but all they did was check to see if there were any codes in the computer and tell me that there was no problem(never go back there again). I did have them change the fuel filter while they had it. Any ideas? What is the correct timing for this engine?

 

I don't know what the corrrect timing should be but you must understand that the main cpu in the truck changes the timming as it needs to ( to where it feels it should be to run the best). Did you try a tune up new plugs fuel filter air filter ect. couldn't hurt unless you did one recently. I think they can put a chip in it to manually change he timing. I don't know much about that though. Some one will chime in if I am wrong. Good luck

Lance

 

I would check that the knock sensor is properly torqued and functioning. A loose or malfunctioning knock sensor can cause false retard, or worse, false advance.

 

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