jumping tach
 

My tachometer is jumping real bad especially when its really cold, (its winter time here). Correct me if I am wrong but isnt it electronic rather than cable driven like the speedo? Anybody had this problem or know a fix?

RE: jumping tach
 

Stock tachometer in gauge assembly?

The tach receives its signal from a blue wire coming from the ignition coil in the distributor.

The problem may be:

1) A faulty blue wire or loose connector A (tach power) or B (tach signal) at the rear of the gauge assembly.

2) A faulty tach.

RE: jumping tach
 

I had this problem with my '80 hatch. Turned out that the distributor shaft had loosened from its bearings/bushings and it was throwing off the tach really bad as well as making the engine sputter a bit. I just went to the junkyard and got another distributor and it was fine after that. However, since that car is much older than yours its probably a completely different problem. Just thought I'd throw it out there.

RE: jumping tach
 

I think you make an excellent point by asking whether the tach problem is linked to any known engine timing problem.

RE: jumping tach
 

well is the tach jumping with the motor or is the motor runing smooth and steady but tach jumping?

RE: jumping tach
 

The motor does not rev crazy, it is the tach. I can be cruising at constant speed and the tach goes crazy.

RE: jumping tach
 

In my earlier post, I mentioned that one possible cause for your tach problem could be a faulty blue (tach) wire. To be more specific, check whether both connectors at the distributor are tightly seated and not corroded and also whether the connection of the blue wire to the igniter within the distributor is tight and not corroded.

http://img237.imageshack.us/img237/6...ure0398er0.jpg

RE: jumping tach
 

you know anybody with a aftermarket tach?

if so run a jumper wire from thier tach to your tach wire, blue under the hood near the drivers fender near the firewall..... and just see if he can cut this tachs signal wire on his tach and just twist yours on the wire and with his cars ignition turned ON start your car up and if his aftermarket tach also goes nuts then its the signal its getting, but if his runs true and your tach is still jumping... then its definatly your tach going back. but if both jump than its the signal and good luck finding the problem area. IMO i would just swap out the distributor...

RE: jumping tach
 

I like this idea. You might also look into borrowing a scan tool capable of making live tach readings from AutoZone.

I disagree with this suggestion of replacing the distributor assembly. It is a very remote possibility that this extreme measure would ever be warranted considering the absence of ignition problems. At most, the igniter unit in the distributor might need to be replaced, although I believe that this too is unlikely. In fact, my wild guess is that the tach is bad. Nonetheless, some troubleshooting should be done to rule out the other possibilities.

RE: jumping tach
 

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