My friend owns his own automotive shop and is one of the best techs I've ever seen. He graciously took time away from his family to spend a few hours with me in my shop, struggling with this Mountaineer situation. What we did:
- Checked fuel pressure.
- Key on results in 65 psi dead on, no issues.
- Pressure while running appears to be in the 67-68 psi range, so the fuel system upgrade does not appear to be a problem.
- Checked cylinder balance using Ford IDS diagnostics.
- Shows that cylinder 7 and 4 are basically non-contributors.
- Seems to be firing, but loading up with excessive fuel on these cylinders.
- Swapped ignition coils, no change in performance. Consistent misfiring.
- Seems like injectors 7 and 4 are being held open and not controlled via the EEC.
- Backprobed MAF. Checks out, nothing wrong with the MAF.
- Swapped to an identical EEC-V unit. REAC4 strategy, EQE3 tear code.
- Had to reprogram it for PATS and other modules, including VIN update and update the key.
- Tweecer RT not installed on the new EEC.
- Fired up and would not idle since the MAF transfer and injector slopes were incorrect, but was not misfiring.
- Cylinders 7 and 4 cleared up and as long as throttle was held, the engine ran reasonably well and smoothly.
I spoke with Adam Marrer of CoreTuning earlier. He mentioned that he's seen that some Tweecer devices do not work well with the last generation of EEC-V computers because of a potential memory space addressing limitation. I suspect I have that issue and that is somewhat confirmed by the fact that the stock EQE3 tune will run the engine without misfiring. Once I plug in the Tweecer, the misfiring madness begins, unfortunately. I may need to switch to using my Quarterhorse for the tuning process at this stage.