Car has been running great for some time now. Not real happy when the temps outside are hitting 90 or so but otherwise no real issues. The P0420 is pretty much a constant thing but I've learned to live with that. I understand why and I might just put in all new O2 sensors and a new cat when the exhaust is refreshed. Got something new now. Started with P1238 which my code reader says is an issue with Injector 2. I would get this now and again. I cleared it a few times. Then coming back from Baltimore a P0302, Misfire Cyl 2 popped into the mix. Thinking it might somehow be injector related and after to speaking to Chad at Detroit Tuned, I swapped the piggyback harness on the #2 and #3 injectors. I'm running the 550's btw. The battery in the Palm Treo was really low so I was only able to clear the codes. Once it has charged I'll be taking the car out for a cruise around town to see what happens now. Digging a bit more into the Bentley Manual I see P1238 is Secondary Upstream MAP Sensor Input. This has me even more confused now. If the MAP sensor was going bad why would Cyl 2 have a misfire. arghh...
Swapping the adapter wires is a good idea to check if they are bad, but i would go the extra step and just unplug them all, inspect them and reinstall. The wires can be rubbed threw from contact with the IC some times or just work there way loose. If one did the others may be doing starting too as well. With your MAP sensor it seems weird, but it's a common symptom to get a misfire code when it's failing or has a fault related to it like a vacuum leak. Since it's an upstream code then it's the sensor at the end of the head over the tranny. Check the wires and the hard gray line that feeds it from the intake pipe. If those look ok then the MAP probably just went bad, it's a common problem on the R53 after it sees some miles. If you do replace the MAP it's important to get the correct one. Both look the same and will fit, but they read 2 different things.
Took her out for a drive. The P1238 did not come back but the P0302 Misfire in Cyl 2 did. Once it cools off a bit I'm going to check the plugs and wires.
Changed the plugs this morning. The old ones didn't look bad. Took it for a long drive in varying conditions. The only code was a P0420 in pending and thats not at all unusual.