'94 Tach Problems

powerstrokes only · #1 (**permalink**) 12-25-2007, 05:27 PM

My '94 IDI Factory Turbo has an issue with the Tach at idle, or when I let off the accellerator when I am driving. It drops to zero until I touch the throttle, then it seems to operate accurately. I would'nt really worry but it has an E40D tranny and when it drops to zero the overdrive light blinks. It is directly linked to the tach, because it quits the instant I touch the throttle. I thought I had it fixed with a new speed sensor on the differintial,( it quit blinking for a couple of weeks) but it started again. Do I need to replace something on the tach? Whole tach system? Maybe clean it where it goes into the engine? If any body has any has any info. on tachs let me know. I am positive my blinking overdrive light is linked to the faulty tach, just have no idea how to deal with it. Thanks!

**SCUFFY828** · #2 (**permalink**) 12-25-2007, 05:31 PM

the tach is controled by the pcm, nowhere on the engine to clean a sensor, the tach itself is probably bad

powerstrokes only · #3 (**permalink**) 12-25-2007, 05:49 PM

This is an indirect injected engine, you can see where it screws into the engine by the oil fill on the front of the motor. I don't think I have a PCM with a mechanical injector pump, I know the tranny is computerized, would the tach be in connection with it? I know very little about a lot, I am really not a very good mechanic, usually just trial and error! Thanks for any help I get!

**SCUFFY828** · #4 (**permalink**) 12-25-2007, 06:18 PM

didnt realize it was idi, yes replace the tach sensor , i think its about 40 dollars , the tp sensor may also need to be replaced to fix trans problem, mounted on the side of the injection pump

powerstrokes only · #5 (**permalink**) 12-26-2007, 06:12 AM

Thanks! I'll go look for one today.

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