Intermittent misfires

Hey all, long time no post. Hope everyone's doing well and driving the crap out of their W8s this winter.

I've been struggling for months with a problem that I haven't been able to find the root cause of. It's getting pretty frustrating, so I thought I'd ask here and see if any of you have ideas.

This all began last summer, when I was driving along happily in the car and it suddenly started to run very roughly. I got a couple of codes on the ECU, P0203 and P0303--cylinder 3 injector circuit malfunction, and cylinder 3 misfire detected. The problem was (and remains) intermittent, but gets worse under heavy load such as hill climbing, acceleration, or at RPMs over ~4000 or so.

Based on the fault code, the logical thing to do was to replace injector #3, which didn't help. The next suspect was the ECU, which I tried to have fixed a couple of times, and eventually just replaced. This helped some, but not completely. The next thing was to re-wire the harness from the ECU to the injectors, which at least made the P0203 go away, but I still get the misfires from time to time. I've replaced all the spark plugs and the coils, with no improvement.

It's pretty frustrating at this point...the car mostly runs great, but when it acts up, it's really a bummer. You can easily imagine how much fun it is to try to nurse a "W7" home when it's missing on cylinder 3.

What else am I overlooking? Any ideas? Has anyone else had a similar problem?

Thanks for any advice or ideas!

Hmmm....hadn't thought of that. It's worth checking. The problem is intermittent, so it might be hard to catch.

Thanks for the idea.

No, but it's been to a very skilled independent shop a couple of times now. They were the ones who re-wired the injector harness.

I wondered about the cam adjuster issue myself. Whether it's relevant to the symptoms or not, it's definitely worth giving the car a preventive shock treatment.