E30 Zone

I have a bit of a problem with the rev counter on my e30 im hoping someone can shed some light on..........

i have a 316i that ive put a m20 2.5 into but retained the 1.6 rear diff (for now). the rev counter was reading way too high so i bought a 2.5 coding plug off zaust on here and fitted it........ rev counter is still reading way too high (rev limiter is way off the end of the rev counter scale)

when the igntion is fully off the rev counter needle rests at 1000rpm........yet when you turn the igntion on the needle returns to its zero stop.

any ideas whats going on here?

Although this sounds like maybe an issue with the engine loom, my old 320i had that little ignition related quirk with its rev counter. I assumed it was just some kind of voltage spike occuring when the ignition was switched off as it worked fine when the engine was running. It's possible then, that your two problems aren't related.