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Hello all,
To make the story short. I got a 1992 f250 7.3 IDI recently with a newly re-built tranny that wasn't shifting properly. I did some research and determined that I needed to change out the old TPS. I did. I then adjusted it to 1.18v at idle and 4.5v at WOT but it wasn't shifting good. I lowered the WOT to 4.3v, then to 4.1v, then to 3.89v and that seemed to make it shift the best. However, it will randomly start lugging (upshifting too early?) and I don't know what the problem is. It drops down to about 1000-1100 rpm when it lugs, mostly on uneven terrain, which is most of the terrain in my area. It also lugs at about 1500-1800 rpm on the highway though that lugging is not as bad as when it does at 1k rpm. I am a super noob at this stuff so any advice would be greatly appreciated. Thank you!
All the shifting in this transmission is done by the computer. The computer looks at engine rpm, vehicle speed, and throttle position. Does anything in your truck (ie the tach) not work? Does this truck have 40" tires?
You mentioned you adjusted the TPS. 7.3l trucks with the E4OD used a Fuel Injection Pump Lever on the side of the IP to control shift points. I've adjusted the Vacuum Regulator Valve on the side of the IP in my 6.9l IDI Bullnose and it has a drastic effect on the shift quality of the transmission. Make sure you get your FIPL setting dialed in. Check it out!
All the shifting in this transmission is done by the computer. The computer looks at engine rpm, vehicle speed, and throttle position. Does anything in your truck (ie the tach) not work? Does this truck have 40" tires?
Tach seems to work fine. Stock tire size. Other than that, all the other stuff that needs work should be unrelated to this. Although when I got the truck the battery cables were burnt to a crisp and the terminals had "bite" marks all over them like they jumped it until everything was fried. I wouldn't be surprised is something else fried. It also has a parasitic draw somewhere that I cannot locate via a multimeter draw test on the fuses.
You mentioned you adjusted the TPS. 7.3l trucks with the E4OD used a Fuel Injection Pump Lever on the side of the IP to control shift points. I've adjusted the Vacuum Regulator Valve on the side of the IP in my 6.9l IDI Bullnose and it has a drastic effect on the shift quality of the transmission. Make sure you get your FIPL setting dialed in. Check it out!
Yeah it wasn't really shifting at all until I replaced that part. As I said, I tried adjusting it to 1.18v at idle and up to 4.5v at WOT but it seemed to shift best at 3.89 WOT.
I'm constantly surprised when I learn about all the things that affect the drivability of these trucks.
Does your overdrive button/light work? Have you checked for codes? If you or a friend has a oscilloscope, hook it up to the FILP leads and slowly sweep the throttle while looking for drop-outs in the FILP's potentiometer.
You mentioned the battery cables were crispy when you bought the truck. Did you replace them yet? While that probably wouldn't have an effect on the way the transmission shifts it could definitely be the cause of your parasitic load.
You mentioned the battery cables were crispy when you bought the truck. Did you replace them yet? While that probably wouldn't have an effect on the way the transmission shifts it could definitely be the cause of your parasitic load.
OP, just wanna second what this guy ^^^ said. Decent chance that's your problem, decent chance it's not. Fix it anyway though. On a vehicle you intend to keep for a while, no sense fixing small stuff when the "basics" like battery cables already have known problems.
OP, just wanna second what this guy ^^^ said. Decent chance that's your problem, decent chance it's not. Fix it anyway though. On a vehicle you intend to keep for a while, no sense fixing small stuff when the "basics" like battery cables already have known problems.
It was one of the first things I replaced. Brand new cables and terminals + I upgraded to a 3g alternator.
I'm constantly surprised when I learn about all the things that affect the drivability of these trucks.
Does your overdrive button/light work? Have you checked for codes? If you or a friend has a oscilloscope, hook it up to the FILP leads and slowly sweep the throttle while looking for drop-outs in the FILP's potentiometer.
It does work. At one point, the OD light started flashing but when I replaced the FIPL not too long after, it stopped flashing. I also tested the other two wires on the FIPL and got 5v on the one and 0 ohms on the other so those are good. I have not checked for codes, I don't have a code reader for that.
Out of curiosity, what did you adjust your FIPL to at idle and WOT? How sensitive is it? Should what I have it set at now be ok? If those settings are ok, could it be a problem with the TECA?
Funny story about the E4OD computer, and Mark K. may be able to back up this claim, but the computer doesn't care where you set the TPS at. When you start you car, the computer looks for the lowest voltage (baseline) from the TPS and assumes the low voltage is at idle. From there, the computer just adjust the shifting and trans pressures based on the baseline voltage. But for the sake of science, these are my voltages when the truck is warm.
Funny story about the E4OD computer, and Mark K. may be able to back up this claim, but the computer doesn't care where you set the TPS at. When you start you car, the computer looks for the lowest voltage (baseline) from the TPS and assumes the low voltage is at idle. From there, the computer just adjust the shifting and trans pressures based on the baseline voltage. But for the sake of science, these are my voltages when the truck is warm.
Interesting. Thank you for that information. So if it isn't the TPS or the TECA. My next step would be to somehow check for dead spots in the throttle sweep? What would cause those "dead spots" if there are any?
Funny story about the E4OD computer, and Mark K. may be able to back up this claim, but the computer doesn't care where you set the TPS at. When you start you car, the computer looks for the lowest voltage (baseline) from the TPS and assumes the low voltage is at idle. From there, the computer just adjust the shifting and trans pressures based on the baseline voltage.
That is correct.
Originally Posted by Prototypemech
Before you get too far, check for codes first. You need a paperclip and a harbor freight test light.
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