Truck: 92' F250 Reg Cab 7.3 IDI with Automatic Overdrivef
Symptoms: Tachometer sometimes works, sometimes does not work. When its working, the truck seems to run good and strong, and then I'm driving along and suddenly, I feel this interruption in power delivery, almost like the truck "skipped" and I look down, and the tach is not working,,,,,,,then later, I feel the skip again, and its working. I could swear it seems to have more power when the tack it working, its like the transmission doesn't shift down right or something when its not working. Is this the tach sensor? Does cleaning it work?
You probably need to replace the tach sensor or replace the wires going to it. You're right, when the tach is working the torque converter can lock up and you'll have more power, when the tach stops working it sends the tranny computer into limp mode which disengages the torque converter. So it's not just your imagination that you have less power. When this happend to me once, the wire going to the tach sensor had broken because i had replaced the connector once with just soldering the wires, the connector was shot. So i resoldered it and off i went.
not to steal your topic but mine is a c6 (idk if that matters) but my tach does not work at all and the tranny is fine plus its a rebuilt may that be why or are all these tranny problems with e4od
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88 F-250 body,550 rear frame setup, 7.3 idi, 3:73 dana 80 rear, srw, dana 50 front, heavy duty leaf springs, back up camera, 20$ wallyworld fog lamps, class 5 bumper hitch welded to frame and gusseted, 32" steering tires all around, ac power converter,jeep bucket seats, deezee runningboards (cab only),cobra 29 cb w/ 102" whip, 2 trucklight worklights on front stake pocket each side,high lift jack behind seat, toolbox for the junk, visor, running lights, 6600 lbs with all my junk
I've inspected the wiring, and even wiggled each one of them at the sensor, and the tach didn't start working while I did that. I guess the problem is truly with the sensor. It used to be, that it would always work as soon as you started up the truck cold, but then after a few miles it quit working and the truck seemed to lose power, so maybe I just need to bite the bullet and replace the sensor. I really appreciate you guy's helping out. This site has some tremendous resources for these great old trucks.
When you take the sensor out, you can test it by using an ohmmeter. with the sensor body not touching or close to any metallic objects, the sensor should give 2000-3000 ohms between the 2 terminals inside the plug. It sounds like you have an intermittent failure though, it might test good for you when you check it but in this case I'd replace it no matter what. The tach sensor sends engine rpm info to the E40D transmission computer, bad data will damage the transmission pretty quickly, so you need to fix this immediately or it's going to cost a whole lot more.
88Beast...the C6 is fully vacuum controlled, the tach sensor is not used to control it.
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1986 F250 2WD Super Cab XLT Lariat w/ 1996 front clip. Dually bed & van rearend (2" wider, allows spring clearance). 6.9 w/ approx 120,000mi. Banks non-wastegated turbo system, Beru ZD1A glowplugs, Delphi BB injectors, Kenworth pyrometer, vac/boost gauge, electric water temp/oil psi/voltmeter mounted in dash. 3" Mandrel-bent open exhaust. C6 trans, 3.54 gears. Okiegringo idler pulley. R134a A/C conversion. WMO/diesel blend in one tank.
when u remove sensor just simply wipe the sludge off the bottom and reinstall.this has worked for me.u can find this trick in the archivies if u want to go back about 8 yrs. back when this was ford-diesel.com
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