chipsto

I replaced the VSS as it was the easiest thing to try first, but the bouncy needle and shifting symptoms persist. PSOM next I think. Chris, I've PM'd you!

chipsto

I think I've fixed the shifting issue! I saw a video on youtube which explained a problem with the PSOM. There's a few components on the board that can go bad but the main one is a varistor. My speedo needle still wobbles but so far it's stopped it's weird shifting issues. Time will tell but after a long drive today during which it would usually start shifting quite violently and at strange times, it behaved itself. Fixing it this way instead of replacing the whole PSOM means you can keep your mileage intact, too. Not bad for $3 worth of parts.

These two videos explain it all quite well:

swanronson

Did you ever solve this?

chipsto

Unfortunately not yet. I've tested the entire vacuum system and it all seems ok apart from the EGR solenoid which I've disconnected for now. I'll be replacing it soon, along with a new O2 sensor.