02 F150 4.2L...Fuel trim

jaandmk · #1 (**permalink**) 11-11-2007, 05:11 PM

I Took the POS+ cable off for about two hours then hooked it back up. I started the engine then watched the engine with my scanner. I noticed the STFT was way off at 20+% (LTFT 0.00) while it warmed up....once the engine was warmed up I saw the fuel trim go to normal. What would cause the fuel trim to be way off while the engine was cold but go to normal once warm??

Moore558 · #2 (**permalink**) 11-11-2007, 05:37 PM

Think about it. When your starting a cold engine, the PCM is going to have it run a little rich in order to get it warmed up and into closed loop quicker. That's should be normal on a cold engine.

jaandmk · #3 (**permalink**) 11-12-2007, 04:02 PM

That does make sense, but its during this time that my lean codes are sent (closed loop, warming up). Thanks for the reply.