2000 Ffv 3.0

I have been having problems with the Tach on my 2000 Ford taurus 3.0 V6 Flex fuel motor 108,000 miles. The tach is just all over the place sometimes works fine then not at all some time just buries itself past 7. Does this have to do with a sensor or is it just a bad motor in the tachometer. Do I have to replace the instrument panel to fix this.

I'm not sure on specifics to the FFV, but in the 80's if this happened on a Ford product the first suspect was typically the ignition module.

There have also been a few people having issues with the flex wiring board on the instrument cluster. I suppose if the tach signal was shorting to Vref it might cause the tach to peg.

Does the engine remain smooth when this happens to your car?

-Rod

The motor runs smooth. The tach is usually at 0 or .5 500 rpms usually if I hit the gas to get on the highway it will peg it all the way and stay there a while even when the car is off. Every once in awhile its normal for a few miles.

The signal for the tachometer comes from the PCM. The PCM gets its tach signal from the crankshaft position (CKP) sensor, so if the engine is running fine and no codes are set, I would suspect that the CKP is working fine.

The tachometer is powered by battery voltage, so if you had an intermittant short in the instrument cluster, you might be able to explain the "0" reading or pegged tach. It would be interesting to run a couple of wires from the tachometer to a multimeter to monitor what the signal at the tach is doing when the readings are off.

An easier check might be to use a scan tool with the datastream mode to monitor engine speed on the scan tool. If it is reading properly, you know the PCM is getting a good signal. The next step (in my mind) would then be to monitor the tach signal at the tachometer.

-Rod