It's a bit of an odd one isn't it! You may be on to something with the replacement computer actually, come to think of it. A year ago, my aux fan started not working even I flicked over to Vent or A/C so I had to bypass that with a manual switch in the cabin (A/C not hooked up but just bypassed the compressor so the fan still works, been that way for a decade without issue). I'm told that's possible solder failure in the PCM. Then sometimes when it's wet or extremely humid weather, my wipers work all weird... some speeds not working, or they just go full speed on any speed setting, or they only wipe when I press the brake pedal haha. And there have been times when I've got a whole plethora of error codes, a bunch of which I KNOW weren't even possible / relevant at the time...
So maybe? Just maybe my PCM is on the fritz and it's dying a slow death. I see second hand ones are about a hundred dollars or more online. If anyone reading this is on or near the Sunshine Coast and has a spare PCM they wouldn't mind me plugging in for an hour or so to test with, that would mean a LOT!!
I can't recall exactly when it last decided to drive like a race car, but it would have been within the last 3 months. I distinctly recall it started with a persistently high idle, like 1500rpm, as if the TPS was on the fritz. It was doing that a whole bunch around that time, which is what eventually prompted me to replace it... But it was just nuts, at 2000 rpm I was spinning tyres going uphill. Today I'm holding 2000rpm on that same hill and craaawwwwllliinnngg up through 40-50kph hahaha. But yes, I'll keep persisting. I might dig out my old stock MAP sensor and hook that up, see what happens. I'll try anything at this point. Essentially, any change is a good sign, because at least I'll know I'm on to something. I will absolutely keep the peepers hooked on those MT2500's and see what I can do, because I've always wanted more detailed information for my XJ. I have a full computer setup for my 95 year 7 series (still OBD1) and man, I can drive around with that laptop hooked up and see more information and do more with it than you'd know what to do with! Having even a fraction of that degree of information for the XJ would be priceless... It's definitely saved my bacon countless times on the BMW's.
Sorry, I know I write stories, I can't help it. I'm too thorough for my own good sometimes!! But again, I really appreciate the insight, you never know what you might miss or forget or ignore
