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I’ve got a ‘91 7.3 with an E4OD behind it and I’m experiencing some issues with the transmission. It’s not shifting out of first until 2500 rpm, and shifts are generally a bit rough. Speedo and tach are working properly, and I haven’t seen the overdrive light blink.
I've checked my FIPL/TPS voltages (sensor side only- I'll try to measure them on the computer side). It was out of spec at 1.2v no throttle. I've adjusted it to 1.1v with no perceiveable impact on the shift timing. I also tried 1.0v without any improvement. The max voltage at full throttle remained around 3.5-3.8v for each.
Are there any other obvious things I should check? I don't have an OBD1 scanner or adapter to check for codes- Is there a way to jumper the diagnostic port to flash the codes on the dash?
I have a few updates. First, the tps/fipl adjustments seemed to have fixed the shift timing issue. Not sure why the new calibration didn't fix it immediately, but the shift timing was fine after it sat overnight. However, it still has an issue in 3rd, and the OD light has started flashing. Went to pull the codes and realized that the self-test connector is mangled and the wires were pulled out.
Thankfully, I was able to find the appropriate wiring diagram with the color codes for the wires:
However, I wasn't able to get the self-test to work. I connected the self test input to the signal return, turned the key to on and pressed down the accelerator (as described in this write up: https://www.fordtruckzone.com/thread...canner.659319/) but the check engine light didn't flash. I'll try it again with a test light just in case the bulb is burnt out. Is there anything else that would prevent the self test from initiating?
EDIT: Yep, the bulb was burnt out. I was able to record the test light with my phone while I pressed the accelerator from the cab. Now to parse through the video and get the codes.
Last edited by Vercingetorix; Jul 3, 2024 at 04:33 PM.
The first two to look at are 93 and 99. They are most likely there due to a damaged wiring harness. If the harness checks out electrically, it could be that two solenoids have failed at the same time, or the PCM has had two circuits fail at the same time. I'll bet the wiring harness is the problem.
29 could also be a wiring problem to the vehicle speed sensor (VSS) located on the rear axle. My first step would be to clear the code and see if it returns.
If the AC wasn't turned off when you ran the codes you'll get this code. You'll also get it if the trans wasn't in park when the test ran.
Would there still be symptoms if 93 and 99 are just the result of a damaged harness? I'm honestly not sure if the ac was "on" or not- The system doesn't work and the controls don't seem to either. I'll save that investigation for a later date.
As for checking the Converter Control Circuit and the Electronic Pressure Circuit leads, are these the right wires to check?
It's been quite awhile since my last update- life is busy as usual. I was able to get an extremely good deal on a parts truck for a ZF5 swap, so I'll be pursuing that once I am able to get her home. But that leads me into my next set of issues.
Last week, the truck has been blowing fuses 1 (Hazard lamps, Speed Control) and 5 (turn signals, backup lights, and the overdrive circuit). It seems to blow them at random. Sometimes they last for 10-15 minutes, sometimes they blow almost immediately. There isn't any clear correlation that I have found between the fuses blowing and any observable phenomenon. The main issue (aside from no turn signals) is that the transmission will not stay in third gear. It will briefly shift into third before shifting into OD (regardless of the state of the OD switch, or vehicle speed), so I effectively have no third gear.
There may be a short in the MLPS, as fuse 5 is in circuit with it- I'll be checking that shortly. In any case, I really need third gear. Barring a clearly faulty MLPS, Is there any way I can hack into the E4OD wiring harness to forcibly disable overdrive or lock the transmission into third gear while in drive? I only need the transmission to get me there and back, so as long as it is drivable, I don't care how much of a hack job it is.
To have it always in third gear you need shift solenoid 1 off and shift solenoid 2 on.
Are you sure it's shifting 3-4? Usually the torque converter locks immediately after the 2-3 shift. With the OD off the PCM prevents shifts to fourth gear.
I’m not 100% certain, but it feels exactly like it’s shifting to OD. It shifts from 2-3 and the rpm’s seem to suggest you are in third, but then the RPMS immediately drop and the engine bogs. It doesn’t seem to be slipping, either.
Last edited by Vercingetorix; Jul 24, 2024 at 05:16 PM.
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