Greetings everyone, from the new guy.
I have a problem that has stumped two dealerships and my local transmission guy, along with all of their contacts. So, I turn to you all to see if any new ideas can be found.
I have a 1992 F150 with the 4.9L and E4OD. The truck has over 200,000 miles on it, and as long as I have had it, it has shifted hard. I had the transmission rebuilt about 3 months ago because I was thinking it is probably worn out. This did not fix the problem.
It turns out that the transmission had a shift kit in it, and that has been completely removed. The pump, regulator, valve body, seperator plate, solinoid pack, all valves, torque converter, stator, basically everything inside the box is brand new. The MLPS is new, the VSS has been replaced, but the only effect it had was to cause the speedo to be very wavy, so I put the old one back in. The PCM, TPS, PSOM, MAP, coolant temp, air charge temp, EGR position sensors have all been replaced, and a new fuel filter.
Some of these sensors were replaced as common sources for the problem I will go into detail about, and some were found to be outside of spec from Ford hooking a break out box to the truck. Nothing has ever thrown a code, but the two sensors that never showed signs of issue but made a significant improvement were the coolant temp, and the EGRPS.
The PCM has been changed twice, the first time to a software version that matches the calibration code in the door jam (F2TF-AXB), and the second time to a software version that should work in a 1995 m/y(F3TF-ZB). No improvement noticed on either PCM, although the newer version may be giving me worse fuel economy.
Now on to the problem:
When it is cold, it shifts into gear nice and smooth, just like it should, about 98% of the time. When it goes into gear, and still cold, it shifts nice and soft with no hard jerks, about 95% of the time. Also, the tc generally waits until 3d gear to lock, about 95% of the time. All other times, and almost always when warm, basically the same percentage of time it works right when cold, it shifts hard from 1-2, then the t/c locks, and the 2-3 shift is very violent unless I lift the throttle in anticipation, then it is still hard but no where near as bad, and the 3-4 shift is hard.
Since the replacement of the coolant temp and EGRP sensors, the 1-2 and 3-4 shifts have been more normal, but they still occasionally slap you in the butt when it shifts.
I just got it back from the transmission guy for about the 4th time, and he showed me with a pressure gauge what is going on in there. In the P to R shift, the pressure spikes to 200 or so, before settling down to 120. In D, and while driving, the pressure stays right at 120. It never lifts for the shifts. I know this is why it is shifting hard. I also know the PCM regulates this, and that is why the PCM has been changed to a newer software version. I was hoping to get a software version new enough to wait until 3 grear to lock the t/c. I can live with the hard 1-2 and 3-4 shifts, and the 2-3 shift when the t/c isnt locked, but the locked 2-3 shift I can not live with.
I am not interested in cutting wires and putting a manual switch in the t/c. I want this thing to drive normally so I can sell it. I am moving to Europe and cant sell a truck that shifts like this.
With that being said, I dont want to dump much more money into it, but I need to get it fixed. I am sure there is a sensor somewhere that is tempreture affected that is causing my problem, but I just dont know what it could be. I am also considering a PCM with software version F5TF-BBC, if anyone thinks that might improve things.
Any ideas?

(sorry for the loooong first thread)

 

Wow, the Ford breakout box... I want one of those.

What drove you to change the VSS?

Adrianspeeder

 

The theroy behind changing the VSS, which I did actually go back and change out with a Ford part since the aftermarket one was screwy and I felt unsure about the old one still possibly contributing to the problem, is that the VSS gets a pulse signal from the tone ring in the differential. This goes to the PSOM where it is changed to a voltage signal that the PCM can understand. If the pulse signal is slightly defective, the speedo will work properly, but the signal going to the computer wont be right, and the computer wont know what to do and cause things like bad shifting. A bad PSOM can cause the same thing, that is why I changed it out too.
Also, since the VSS also supplies the signal for the rear ABS, and since my light is on, it was a one shot, two kill attempt that missed both targets. The ABS light is still on, and the transmission still shifts hard.
New work done has been to change the EGR actuator valve. This didnt help anything either. The idea here was that since the EGR position sensor had such a profound effect on how things ran that maybe there were more problems with the EGR system. Does anyone know how to check the EGR valve itself? Back in the old days you could squeeze it with your hand and see if the engine coughed. It doesn't appear to be that simple on this.
Does anyone know if any of the emissions sensors could cause these drivability issues? I would think not, but I am kind of at the end of things to check. I also wonder if low fuel pressure could cause this, even though the engine runs fine. I have no difference in performance from either tank, but that isnt to say the regulator isnt fully doing its job.
From what I can tell the only sensor I have not replaced is th O2 sensor. it passed smog testing with flying colors, so I doubt it is faulty. Can anyone think of any sensor(s) I may have missed?
I am really begining to wonder what parameters the computer looks at when it decides to lock the TC. I think this is the key to the problem. One of these sensors, or wires may be faulty, causing bogus readings to the PCM.
My final thought is back to the F5TF-BBC software version PCM and whether it only locks the TC in 3d and 4th. If it does, it would make a good band-aid for a difficult problem. I could live with the stiff shifts if I can get rid of the violent 2-3 w/TC locked shifts.

 

Pull the vacuum hose off it, connect another hose to it, and suck on the hose.

 

Sounds simple enough. I'll give it a shot.

 

Hey Linus, I know this is along shot, but maybe it's worth a try. I've been going through some issues myself, mainly related to TPS and IAC codes. I had replaced the old IAC and kept the old one. Recently, when the mornings are cold, but the afternoons hot, my motor is going nuts with RPMs and stalling. Me, being the buttnut I am, would fix this problem by switching out the old IAC with the newer one. It would actually straighten out the issue, but only until the PCM realized what I did. Then I'm back to square 1. Point is, when I put the old IAC back in, I would get hard shifts. Not as violent as you're describing, but still not right. Of course, that's only my own personal experience, but hopefully it'll help you out. Good luck with the truck, and enjoy Europe. Peace, Dave.

 

What is the IAC?
I tried sucking on the EGR and it moves and holds vacuum.
I'm really wondering what sensors the PCM gathers information from to decide when to lock the torque converter, and if these same sensore would tell the PCM not to drop the line pressure during the shift. Being that the O2 sensor is the only one left on the engine that I havent replaced, and maybe the IAC thing, could it be that the solenoid pack in the transission is bad, the same way the original one was?

 

Idle Air Control.

When you sucked on the EGR, did the engine stumble or stall? You gotta do it when it's running.

 

I'm having the same issue with my 1992 F150 5.8 I also replaced the VSS. The ABS light is still coming on which is weird. My transmission friend said that it could be the solenoid in the transmission is bad but I have yet to look into that. My other mechanic friend said that my truck is clunking into gear because the IAC is dirty/going out causing the truck to idle high, I was going to try cleaning it before I buy a new one. But would the IAC make it shift hard all the time or just when I'm putting the truck into gear?

 

If you unplug the electrical connection to the IAC does the engine idle speed slow down? If the answer is yes, a sensor is bad. Probably the throttle position sensor. You may want to pull the codes before you buy a throttle position sensor, only a genuine Ford throttle position sensor is recommended.

 

I remember something about the dome light screw pinching the wire and blowing the fuse. Been a while, though. This also came with other symptoms on the dash that I can't remember. Anyway, check all your fuses.