Back story- My '05 MCS, at 160k miles, started gagging and choking during steady state throttle up the canyon to home in April of this year. Pulled the codes, P1109, P1239, all pointed to bad MAP sensor. Replaced the sensor with a new one-WORSE!, replaced with old one -better, but still throwing codes off and on. Took it to an Indy shop- they tried to tell me it was the ECU, sent ECU to FL for check out- It was fine, shop says "see, it was the ECU" BS-never going back there. I found that the #2 plug wire was burned through the middle of the boot and arcing causing a #2 misfire.changed plug wires. Two months later, it starts up again.
Made an appt, took it to the dealer, found a torn intake boot, replaced the throttle body-shaft was sticking. All was good for a few months, since the end of the AX season, its started up again, took it to the dealer, said they found an open in the Aftermarket chip wiring (UniChip) disconnected it, they checked the MAP sensor, said that it read fine, it ran fine. UNTIL I pulled off of the freeway going home. It was arcing around the end of #2 plug wire again, Cleaned the plug wire insulators, replaced the coil pack, Still does it.
It intermittently will die at lights, surge at steady state throttle, when it does this, it also will not respond smoothly to throttle input, rather it pauses and then surges forward. SES light stays on, DSC light on sometimes, no trifecta, just P1109. I'm stumped and apparently, so is the local dealer. The only other thing in my mind is the TMAP Sensor after reading all of hte other P1109 threads.
Could the Bypass valve be a contributing factor, it does have 160k with 8-10 AX a year and a few track days here and there.
Input?
TIA, Mark

 

Some of the power issues could be bypass valve, I suppose... But I'm also thinking that if you're having some electrical problems, maybe check all the grounding points and make sure they're making perfect contact.

 

That's worth a look, When the problem first presented itself, I had the battery checked, and cleaned all of the grounds, etc. But that was over a year ago, so its worth a go.