Bouncing Tach

I just bought a 82 911 SC with 136,000 (1st Porsche) which runs great and has good records. Last night after I got on it a bit getting onto the freeway I noticed about 15 miles later the Tach needle was bouncing about 1500 rpm each bounce, but the engine was running smooth. The engine quit at a stop light. It started right up and about 2 miles more as I was pulling over to stop. The engine quit and all the power was gone (like the battery was disconnected). I checked the fuses and battery, which were good then tried the key again. It started so I parked it. 2 hours later I went home and everything was normal. Anyone have any ideas?

The coil runs your tach, and also gives your distributor power so it can fire the cylinders. I'm thinking you have something loose on the coil--ground wire?--or the coil may be going bad as it gets heat soaked after driving it awhile.......again.....it's just a maybe.....

Bruce!
Had a similar problem with my 86' 911 last year. It ended up being a coroded ground strap from the battery that was not grounding the car properly. $ 11.00 dollars later with a new strap the problem was fixed!

Good Luck!

Huey581
86' 911 Cab