Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I have a 99 f150 4.2l with a p0171 code. I have changed every sensor. Resealed the intake 5 times. Most recently swaped the lower intake with a new dorman.the issue I have is bank 2 ltft are at 12.5% at idle and move to near zero at 3k rpm. I have chased a intake leak all up and down the truck no leak found. What else could be throwing a code on just bank 2. I don't know of a way to test the injectors in the truck. Besides swaping them to the other bank. Also egr system is all new,brake booster and evap have been plugged and ruled out. I'm down to either an injector issue or bent valve. Keep in mind that the truck runs great except at idle it has higher than 10% ltft on bank 2. And a hesitation when you idle for an extended period like sitting at a red light. Any help is greatly appreciated.
Last edit: 6 months 3 days ago by Blake Hurst. Reason: Spelling
Positive 12.5 total trim at idle is a problem, but likely not enough to set a lean trouble code on a truck that old. I would be interested in the freeze frame data to see under what condition the po171 set, and also what the fuel trims look like on bank two.
Bank two could be equally lean but just not setting a trouble codes yet, then you would know if you need to look for something bank specific or something that effects the whole engine.
Of course, if there is a misfire, this must be corrected first before attempting to fix fuel trims. as Lupe pointed out, it may be beneficial to verify engine integrity and spark output.
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