Tachometer Problem

[gcooper8]

Greetings, I have a '97 Ranger Super, XLT 4x4, auto tranny with 4.0L engine and 140k. Recently it seems the tach has taken up retirement like me and only works part-time. Usually at higher RPMs it registers something, but idling the needle will drop down to "0." I have not been able to find info about this in my Haynes manual. Can someone tell me where to look for the sensor that reads RPM? Or is it more likely the gauge in the instrument cluster? How can I fix this? Thanks, geo

[Rockledge]

Sounds like a gauge problem.

On your '97, the tach gauge receives the tach signal directly from the PCM. I think it's reasonable to assume that the tach signal circuit is good up to and including the PCM, otherwise you would be experiencing other symptoms and/or trouble codes would be set.

[gcooper8]

Thanks. How would I solve the problem with the gauge itself?

I do have DTC P0443 but did not think that would be related to the Tach. What codes might occur if it is something other than the gauge?

I haven't solved the problem of the P0443 yet either.

geo

[Rockledge]

P0443 - EVAP Control System Canister Purge Valve Circuit Malfunction

The PCM monitors the EVAP canister purge valve circuit for an electrical failure. The test fails when the signal moves outside the minimum or maximum allowable calibrated parameters for a specified purge duty cycle by PCM command. Possible causes:

l VPWR circuit open
l EVAP canister purge valve circuit shorted to GND
l Damaged EVAP canister purge valve
l EVAP canister purge valve circuit open
l EVAP canister purge valve circuit shorted to VPWR
l Damaged PCM

A good summary of the EVAP system in general can be found here: http://www.ford-trucks.com/forums/sh...18&postcount=3