tach bounce

has anyone had trouble with tach needle bouncing? I have a 88 930 and all of a sudden it is starting to bounce. Is it getting ready to go? thanks for any help.regards jer

Mine wiggles just a little occasionally, and I'm wondering the same thing.

Didn't I hear some crazy story once about speedometers that kill ignition units?

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'83 SC

I seem to remember the same thread superman..that's why i'm worried ...can anyone else comment. thanks jer

Superman and Jer,
I've had the same problem before, and I found out on this post that it was caused by dirty points in your distributor. I cleaned mine and they haven't bounced after that. I switched to electrical ignition (Crane/Allison one sold right here on Pelican) and I've never seen my tach needle bounce anymore. Good luck.

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Jeff
1976 911S

Thanks Jeff but i have a magnetic pick up that signals the cdi permatune.Any other ideas would be greatly appreciated regards jer

I have a 86' 911 Cab that had the same bouncing tach needle. It was initially diagnosed as a short in my battery. When the battery was removed to put in a new battery, the ground wire to the battery was found to have been rusted and not grounding the car properly. New $ 18.00 strap installed, no more bouncing tach! Good Luck.

Huey58
86' 911 Cab

I seem to remember other posts referring to bouncing tach being related to bad ground and/or unregulated alternator - it may pay to search for that.


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Cameron Baudinet
1975 911S

hey thanks i'll check out your ideas..all help is much appreciated regards jer

I'm still listening too. Seems I need to take my own frequent advice and clean some important electrical connections.

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'83 SC

I guess on the 88 930 there is a single wire that comes out of the 6 terminal connector at the cdi. This runs along for about 10 inches and there is a 3 prong disconnect. Mine has pulled apart slightly and i think this is the problem area. thanks jer sorry that's a i prong connector the 3 prong is for the oxy sensor same area.....jer

[This message has been edited by RJM3 (edited 08-28-2000).]

I recently fixed the same problem on my 89 930. My alternator was spiking at around 18 volts. Replaced the alternator and all is well. Check your voltage with a voltmeter, should be under 14 volts. If not, probably the Alternator.

Hey Rayz, I've checked with digital volt meter across battery and at different rpm's it stays between 13.45 to 14.00. but the tach keeps jumping.when i turn the door lock switch it jumps Voltage surge? would i eed an scope to pick this up? just had alt rebuilt 2 months ago????any comments or any help would be appreciated...thanks jer

I am not an expert on Porsches from the 80's, so please ignore this if it is not relevant. I was riding in a car by another manufacturer when it hesitated. I watched the tachometer bounce a couple of times. Then, the tachometer fell to zero and the engine died at the same time. The driver was unable to restart the engine.

When the car was towed in to the shop, it turned out that the magnetic pickup in the distributor had failed. Is it possible that the magnetic (or optical) pickup in your distributor is suffering intermittent failure?

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Bob Thayer
1971 911T
rthayer@hdrinc.com

Thanks Stinky,I've checked with ohmeter and it shows within specs 675 ohms and it toggles back and forth when cranked over? It is just so intermittent....Today the tach jump all over and stalled at least 4 times starting up each time then i drove home at 80 with not a miss????permatune i don't know...frustration...I am borrowing a bosch unit tonight and will drive it to see if it is the cdi permatune...thanks jer Could the magnetic pick up be intermittent???

[This message has been edited by RJM3 (edited 08-29-2000).]