My 171 code was caused by an exhaust leak....
Ya, he took it back to the dealer and had them do it again while he watched.Did your friend go back to the dealer about the PCM flash? If the car had nitros and possible a SC, it's probably still tuned for those things which would really screw up the tune since they are no longer installed.... With all the stuff you've changed, and since you haven't found any exhaust leaks (which is what I suspected to be the problem), I'm leaning toward a really bad tune or maybe even a faulty PCM. Have you checked the ground for the PCM?
Problem is that it is going so lean the PCM has a hard time rebounding from the lean condition and fights to bring it back, which is when it trips the pending code.Going lean when you let off on the gas is normal. That part of it is nothing to worry about.
Any way your buddy can capture some logs for us to look at?
I know, but he is 100% sure there is not a leak. Couple other things i didnt mention, remember before the 171 would always pop first and then the 174. We swapped the injectors around and that didnt change, but after all that other stuff and eventually we fixed it and she ran fine for about a week. Then the codes came back, but this time its the 174 that pops first followed by the 171. So i ordered a set of FMS 24lb injectors. But the codes came back as well as the high idle issues.What I'm still thinking.
I found a service tip put out by ford if you like I can e-mail it to ya. Not sure it will help much but it is good reading. Let me know.
Check this out. It can take a while to set everything depening on how he is driving it.
http://www.obdii.com/drivecycleford.html
The codes will only get triggered when the car is running in closed loop because it happens when the learned fuel trims pass a pre-programmed threshold. The car runs in open loop for a couple of minutes (a bit longer when cold) on starting, and at WOT, for example. But during normal driving, it runs in closed loop, always learning the typical adjustment required from the O2 sensors. That is when your codes will usually be thrown.
The PCM compensates for IATs, so that should not be the root cause of the lean condition.
That said, the less hot air you can pull in from the engine compartment, the better your car will run. Pulling the snorkel could make it easier for hot engine compartment air to get in, but I never liked the stock air box with or without the snorkel. I prefer a system that has less room for hot air to come in. Unfortunately, the Volant CAI I use is no longer available for our cars.
Installed a Catch Can to try and cut down on the oil getting into the intake. Going to install a second one as soon as I find another one to make a matched pair.
That catch can how functional/effective is it as opposed to the smaller Glass/Plastic canisters?