Dead speedometer

[4cefed]

So starting about a year ago my speedometer needle would quit and drop to zero usually after hitting a large bump. Sometimes after a few minutes it would come back or next time I shut off the car and restarted it would be fine. Eventually it just stopped working altogether (including the odometer).

I had a spare cluster from the parts car and I tried to switch them out. When I installed this one, even with the car not moving the needle would oscillate wildly between 60-80 mph and down to 30-50mph and back up and down. It was twitching more than anything, then it would just peg out high. Now after a couple weeks there is no response. The odometer still doesn't work. I was just going to swap out the speed sensor only to find out it costs and average of $150!

Has this happened to anyone? I have the FSM so I'm sure I can find out if the speed sensor runs on 5V like most sensors and try and test it somehow. Should I get a pulse signal out of it? Some kind of waveform? Just check for resistance? I would try a brand new cluster but I'm not sure if I can even purchase one, I looked briefly.

Recently the car developed a bucking and hunting for idle issue which I'm thinking is TPS, or IACV, or EGR. Does the speed sensor have input to the ECM with these cars? I know with the Chrysler Manifold Absolute Pressure systems that if the speed sensor goes bad the car stalls when you put the clutch in. Not sure if that's the case with MAF systems.

Well not the end of the world, but if anyone has been through this any help would be appreciated. Car is a 92 with a 91 KA24DE, manual trans.

[solallein]

Sounds like an intermittent short, or something wrong with the speed sensor. The speed sensor does not effect engine performance unless you have an auto trans. To test it you just check for a resistance of ~250 Ohms, and 0.5V between two wires on the gauge cluster while spinning it by hand. I would also pull it out and check that the plastic gear isn't trashed. Mine was acting funny and the gear had worn down because it had actually popped out of place.

[4cefed]

Thanks for the info! It's getting a little cold here so I'll play with it when the weather warms up a bit. I'm hoping it's a loose connection on the plug or something. If anyone is reading this thread about the bucking problem, I fixed that. One of the wires got pushed out of the connector fro the TPS, I pushed it back in until it latched and it's fine now. I think the torque on the engine was connecting the loose wire intermittently so it would run ok under acceleration.