Injector vs mixture..

[Spocket]

I'm having driveability issues since the last 20 000 KM and now I'm gonna bring the car to the dealer to have it checked. It's the low throttle/low rpm bucking & jerking problem I posted about that previously in the problems section.

I wanted to put the OEM intake back to bring it to the dealer so they will be less likely to tell me that my aftermarket stuff is causing the problem, or that they won't work on an engine with those modifications. I left the SVT UIM, TB and 19 lbs injectors but I slapped back the stock intake from the gooseneck to the airbox including the stock MAF. After only 50 miles coming to work this morning, my CEL is on. I still have to pull the code but I can guess I'm throwing "rich mixture" codes.

With my 75 mm MAF & 19 lbs injector, my long term fuel trim was around -20% (OBDII). High rpm MAF reading on the SAFC was about 33% usage. I guess that with the stock MAF back, I'm now exceeding the fuel trim limits. The SAFC now eads 42-43% air flow usage at high rpm with stock MAF. It shows the difference in calibration of the 2 MAF units. Interesting since the calibration of my pro-flo MAF was always a mistery.. ordered for 17 lbs but came with a spec sheet for 19 lbs. The difference in calibration seems huge for an injector size of only 12% bigger (19/17). Witht the stock intake I shall let less air go through if anything but I still read that 25% more air pass through by the stock MAF vs the Pro-Flo. Strange..

I imagine that if I reset my ECU again, and set the SAFC to around -20% (or match to whatever my current longterm fuel trim is) everywhere including the low and high throttle settings, I shall be good to run without CEL to bring the car to the dealer? Is my line of thinking all right?

[exigent]

I doubt they will touch it with the afc installed.... Dont worry about the svt stuff.. they will ignore that.. they have ford part numbers.

If i were you... id have them investigate fuel pressure. Ill be $5 that when it bucks the fuel pressure is droping. MAKE them hook up a fuel pressure gauge and run it in through the window..... drive and make it buck and watch that gauge drop like a rock. Thus. You get a new fuel pump :)

[Spocket]

The fuel pressure is nice and constant to 70 lbs according to my OBD-II scanner. Is it a good tool to monitor that? i.e. is there a fuel pressure sensor and if so, is it accurate enough to use it to monitor such problems?

[Spocket]

Also, I'm out of warranty so I'm gonna have to pay for the repairs.. still think they would refuse to work on the car even in that case because of the SAFC? I can always Hide it.. I either have to let it there or change back the injectors (*argh*) before bringing the car to them otherwise I pull a CEL with rich bank 1&2 codes within 50 miles driving. I'm also on the clock cause I leave for germany sunday morning. My girlfriend will take the car to the dealer while I'm gone.

[exigent]

Oh... yer outa warrenty? Hrmm... never mind. The only thing i worry about is its not fair to not tell the mechanic what youve done. SO..... either make it stock or tell him all about it.