Tach spikes past redline and stays

[Eighteen80]

Hey everyone!

At startup, and the entire time driving, the tach is spiked past redline. The car drives just fine, I just shift by sound. I've searched quite a bit and can't seem to find anything related to this. I'm thinking it's not the TPS since the car is idling fine. Any suggestions on where to start? The rest of the cluster is operational.

I just purchased the car on Tuesday and this is my first venture into E30s.

The car is a 1985 318i

Thanks!
Andy

[dnguyen1963]

Check your SI and cluster board for corrosion or broken solder.