tachometer jumping, jerky shifting

91FORD7.3

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I have a 91 7.3 IDI with E40D and recently the tranny has been acting up. It does not do it all the time only intermittently. The tachometer starts jumping all over the place and it tries to shift in and out of overdrive. It will jerk like crazy too. It only happens at speeds over 50 mph and seems to be worst on inclines or when pulling a trailer. It has been to the dealer twice now and I am sick of spending all this money for it to still be acting up. First time, they replaced cam sensor due to code 42 showing up. Problem still occured immediately after I got the truck back. Second time, they replaced the alternator because they said it was failing and causing this. Problem solved for a week. It just started doing it again this afternoon. Has anybody had this problem or know how to fix it. I am at my wits end with the dealer. Please help!! Thanks in advance!!
 
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SKimballC

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Sounds like it must be your tach sensor on the fritz. Its in the timing cover to the right of the oil filler with 2 wires coming out of it. It's crucial to the operation of the E4OD. Takes about 30 seconds to change out.
 
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pafixitman

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Here are my notes on the E4OD...

The E4OD gets signals from the FIPL (or TPS) Fuel Injection Pump Lever, the tach sensor and the rear anti lock brake (RABS) / speed sensor on the rear diff housing. Check the FIPL first.

The TP (FIPL) sensor is incorporated to provide an electrical signal, which is proportional to the amount of fuel being delivered, as an input to the Transmission Electronic Control Assembly (TECA) Based on this information, the TP (FIPL) provides the proper shift scheduling and torque capacity.

Should a malfunction occur in the TP (FIPL) sensor circuit, the electrical signal sent to the TECA will be recognized as erroneous. When this out-of-specification signal is detected, the TECA will provide a high-capacity operating mode that protects the transmission from potential damage. This operating mode includes maximum TV pressure, resulting in harsh upshifts and engagements and a singular shift schedule regardless of accelerator pedal position, resulting in the 1-2, 2-3 and 3-4 shifts occurring at a speed commensurate with a heavy (but not wide open) throttle setting.

The Ford shop manual has a procedure to set the FIPL sensor. It's fairly long and required a special gauge block and the use of the Super Star Tester (early scan tool). I decided that this was not what the "field" needed so I called the Ford Hotline and they gave me plain and simple voltage readings at closed throttle and WOT. MUCH easier.

Closed throttle voltage = 1.1V
WOT min 0f 3.8V not to exceed 4.3V

You definitely don't want 5V at WOT. PCM would read this as a short between Reference Voltage (5V) and FIPL signal and go into failure mode.

Next, does your tach work? Bounce? If it does not work, or bounces, then replace it.
The dead tach sender should/would send the automatic trans into a "failure management mode" (limp mode) with harsh engagements and firm shift feel, and an abnormal shift schedule. It has no effect on a manual trans only the Tach readings.

Replace the tach sender on the oil fill housing a big 1" nut with 2 wires. Ford only part Engine RPM sensor E5TZ-17B384-A about $50. You can remove and clean it but usually changed later too. You can test it too, hold it in the air away from ferrous metal, using an ohm meter lead on each wire you need DC resistance between 2000-3000 ohms.

Does your speedo bounce? If so replace the sensor on the rear diff.

If all of this "passes" then check all of the electrical connections at the tranny it self. Remember to replace the heat sheild on the pass side of the tranny when checking the connector.

Now, after all of this is done, replaced and good, remove both negative batt cables for about 15 minutes, this will reset the computer.

If you have not already done so, invest in some nice plate style coolers (I run two), a temp gauge and go to the local dealer and get a trans pan, gasket and filter for the 2001 F250 4X4 with a 4R100 trans. This will give you an extra 1 1/2 qts of capacity and a drain plug. Magna Fine makes a nice disposable in line filter, or you can add an external filter of choice. As another member says "a clean, cool fluid is a happy fluid."
 

91FORD7.3

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Thanks for the speedy replies!!

I really appreciate the quick answers. The tach works fine and does not usually bounce. The speedometer bounces at highway speeds and will jump all the way up to past 85 mph and stay pinned until i let off throttle. I will go over everything you told me and hopefully fix this sucker. Thanks Again!!
 

Agnem

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Doesn't really matter. If either one of them is messed up, so the tranny will be.
 

Mont91

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Remember the '91 uses a speedo cable for the speedometer and a speed sensor for the computer, both on the tail shaft. "92 and up use the rear axle speed sensor. The bouncing speedo is a cable issue and does not affect the "91 tranny.

The tack should never bounce for any reason at any time, if it is this will mess with the computers mind and cause all sort of tranny issues. Clean the tach sensor to start with.
 

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