Lean condition still ?

[01BlkLightning]

U7158 vr902 01 lightning
So after checking for vacuum leaks and all that jazz I took the truck to the dyno shop and cant seem to sort it out. THe fuel trims are not trying to compensate and while on the dyno the a/f ratio stayed consistent throughout the entire run. The truck put down really good numbers but the 171 , 174 lean codes still keep popping up. The guy at the shop wants to just keep throwing fuel at it, which as you guys said doesnt seem right. Any help you could offer would be great. At least what should I try next.

[J-Rod76]

If it makes you feel any better my 01 L is doing the exact same thing. I'm pulloing my hair out trying to figure out what is causing it.

[dbqking]

As a mechanic in the feild I can almost assure you there is no way your fuel trims are ok all the times.......I would start by checking the freeze frame failure in the PCM it will give you a snapshot of the engine conditions when it set the code. Engine temp,rpm,fuel trims, etc.I have had cars get to me with these codes and great fuel trims and then I find out through the freeze frame faliure that when the engine was cold the fuel trims were aweful setting the code. fords are good for this.Intake gaskets normally the cause and then the engine heats up expansion happens seals the leak and the fuel trims go right in spec.adding fuel doesnt seem to be the fix!

[dbqking]

Only thing is to check this you will need a real scanner to see freeze frame failure not the predator or an auto zone scanner

[mikel]

The 171/174 codes have nothing to do with WOT perfrmance, they are happening at part throttle, in closed loop, and they set when your fuel trims reach their max range (I think +/-33% on fords?). Adding fuel at WOT is pointless in this case, especially if the WOT A/F is already good.

What you need to do is log the fuel trims, or check the freeze frame data, and I bet you'll see the trims getting way out of line at some point. Most likely issue is a small leak somewhere as has been suggested.

Thanks

[01BlkLightning]

WILL A SMALL LEAK ALSO CAUSE THE IDLE TO GET ROUGH AND THE SETTLE BACK DOWN? SINCE THE GUY AT THE SHOP TUNED THE TRUCK IT SEEMS TO BE DOING THAT ON A REGULAR. THEY CANT SEEM TO FIGURE OUT THE PROBLEM EITHER AND i AM STARTING TO QUESTION THEIR ABILITIES. I HAVE RELAYED YOUR GUY'S INPUT TO THEM AND THEY ARE GOING TO TRY REPLACING THE MAF SENSOR. THANKS FOR THE HELP.

[maroonefordftl]

Ck the pcv hose,they get soft and leak where it hooks to the lower intake.
Cause codes p0171 p0174
Good luck

MB