Hey, Im new to all of this and I have had my 94 idi since april. It's Speedo needle twitches like crazy no matter the conditions (hot, cold, low speeds etc...) How ever this doesnt bother me because it stops losing its mind long enough to see what speed i am at so i can just memorize what speeds are what rpms, Anyway, my main question is will this effect how acurate the odometer is? Or am I just an Idiot

 

I'll leave the last question to the ones that know you best.
There are days of reading here on speedo problems.

 

Thanks and I feel like most that know me would agrre that I am

 

Yes, most likely the odometer will be off as a result of this. With an old-school cable-operated speedo/odo, when it fluctuated, it was usually from the cable binding and releasing, therefore rotating faster and slower. But those fluctuations essentially cancel each other out; at the end of the day, the cable still turns X number of revolutions, whether it's jumpy or smooth. So that translates to Y miles on the odometer in either case.

A jumpy electronic speedometer indicates a sensor or signal issue. Either the wiring has an intermittent short, or the sensor (VSS) is failing intermittently, or there's foreign matter in the diff oil or on the tone (reluctor) ring on the ring gear. All of these effectively feed a zero MPH signal to the speedo/odo (PSOM) for a split second. So most likely, all those times the needle is dropping, the odometer is counting less distance than you're actually going.

The exception to this would be if it's the speedo head itself that's not positioning the needle properly. But a jumpy speedo like this is more likely to be at the VSS or in the connector or wiring. It may be too little fluctuation to make a significant difference. You could always try measuring against a GPS.

I'm guessing you have a manual transmission....

 

Yes i do have a 5 speed manual and it is an electronic speedometer, thanks for the info it is much appreciated

 

It could be a bad PSOM or a bad or dirty VSS or ABS sensor on the top of the rear axle. It is also likely a bad connection damaged wiring near the axle. Once I had an issue that could only be resolved by disconnecting the RABS module behind the glove box.

 

Will look into that, thanks