MNSubbie

I am troubleshooting some issues on a Truck I just bought. It is a 2006 with a 5.4 (171K miles) and has a miss at idle that goes away when the rpms get up to about 1500. It does set a 301 code, and a new COP did not help.
I know there are several other things to check, but in investigating this I have looked at fuel trims.
Noticed that at idle the LTFT for bank 1 is at +15 or so, which is way too high and seems to indicate a vacuum leak. Bank 2 appears normal
Also noticed that at 2000 rpm the readings are reversed; Bank 2 reads about +15 and Bank 1 is normal.
What would cause the problem to switch banks?. How could the vacuum leak change from side 1 to side 2?
Is this a Throttle Bode or EGR issue? Any ideas or advice would be appreciated

RLXXI

LTFT long term fuel trim is NOT what you should be looking at, it's STFT short term fuel trim that will aid in diag of the problem.

You say you already changed the COP, coil on plug, but did you also change the plug itself?

I suggest you take your truck to someone that knows how to diag the system.

Not trying to belittle you just saying in order to repair the issue requires someone that has had formal training in Ford OBD II.

.

jamie930

When was the last time the plugs were changed?
If you dont know change the plug and COP boots
Also have you checked your FPDM Fuel Pump Driver Module? Its on the frame rail above the spare tire. They are known to rot out and cause problem seeing how this module control the fuel pressure