I've been dealing with intermittent poor idle/cutting out with my '87 240 with 192k miles on it for a few months now. The problem feels awfully electric, and I've ruled out distributor and ecu/icu problems by swapping in replacements. I'm also almost positive that the fuel pump relay is fine after a close inspection of the soldering. Here's the clue I have: the shift indicator light in the dash stays on all the time, and I got a bulletin from Volvo that told me how to do an auto-diagnosis on it, which I did and accordingly indicated that I need to check the trigger (RPM) signal from terminal 1 of the coil to the shift indicator circuit. Here's the question: if the signal from the coil is getting botched going to my shift indicator, could the icu be getting the same signal and misinterpret the timing? If so, what would be the most likely culprit... the coil or the dreaded wiring harness? I kind of doubt it's the wiring harness, just because I haven't noticed any other strange quirks happening yet. Of course, it's really just that I'm hoping it's not the expensive fix. Has anyone else had a coil problem like this before? Any ideas, suggestions, things I'm overlooking? Thanks a ton!

Paul