Lockup Trouble

[lmoas]

Have a ‘96 Prado 90 1kzte with roughly 160k KM on it, new owner. After a few weeks with it developed rpm jumping at 80kmh, where the rpm would jump up 200-300, then drop down, then back up, as long as the car held at that speed.

Was inconsistent at first then gradually became constant.

Of note sometimes would eventually disappear after long highway drives, 30+ minutes, but less than that, and it’s a constant issue.

Have had all solenoids changed, new fluids/filter, even a rebuild, and the damn problems back.

I’ve seen a few other threads even one where someone mentioned the EGR being the culprit. Have not done any grounding checks or ECU inspection.

What else could I be missing? I think it’s pretty certainly not a primary trans issue, unless the valve body is bad.

I checked to make sure the brake light sensor wasn’t engaging too easily, have not checked the TPS yet. At one point I did tighten the kickdown cable which temporarily fixed things before it came back.

Anyone have more insights? I even tried pulling codes manually and the car didn’t return any codes, just the normal O/D flashing when checking.

 

[SPeve]

This could be very similar to what I experienced recently on a small road trip I had to take for work. The drive was about 100mi each way. On the drive back, it was very hot out. I think the heat index was pushing 100'F and the gauge on the center console was reading 32'C, not sure where it gets that number but I believe inside. As I was cruising along, about 85-90Kmh, it felt like the transmission was slipping or surging. Hard to describe but it felt like it was being pulled forwards, then backwards a little. It did this for about half the trip, then mysteriously went away. I used the A/C sparely since I was worried about over heating.
I also recently did a drain and fill on the transmission, about 3.5 - 4 qts but can't quite remember how much I drained. Just that when I filled it back up, it was near the top of the dipstick (cold) if memory serves correctly.

I know this doesn't quite help you out but if your engine RPM is surging, it could be related to throttle. Either the kickdown cable or perhaps throttle body. Might not hurt to start there and even clean as you go. :-/
Hopefully you find the culprit.

 

[lmoas]

This could be very similar to what I experienced recently on a small road trip I had to take for work. The drive was about 100mi each way. On the drive back, it was very hot out. I think the heat index was pushing 100'F and the gauge on the center console was reading 32'C, not sure where it gets that number but I believe inside. As I was cruising along, about 85-90Kmh, it felt like the transmission was slipping or surging. Hard to describe but it felt like it was being pulled forwards, then backwards a little. It did this for about half the trip, then mysteriously went away. I used the A/C sparely since I was worried about over heating.
I also recently did a drain and fill on the transmission, about 3.5 - 4 qts but can't quite remember how much I drained. Just that when I filled it back up, it was near the top of the dipstick (cold) if memory serves correctly.

I know this doesn't quite help you out but if your engine RPM is surging, it could be related to throttle. Either the kickdown cable or perhaps throttle body. Might not hurt to start there and even clean as you go. :-/
Hopefully you find the culprit.

I did inspect the throttle body a while back and it was really clean, didn’t remove it though. I guess TPS diagnosis is next. What’s the best way to do this? Do you just pull it and apply a multimeter to it while manipulating the pins?

Problem came back. It disappeared a day or two after the rebuild, now it’s starting to return.

 

[lmoas]

Pulled ECU out of curiosity.

Had a recent long drive, 12+ hours highway driving which I know might not have been the smartest idea given the lack of a diagnosis.

Problem was intermittent the whole drive. I feel like sometimes playing with the AC and cranking up the heat also affected the behavior, and at certain points in the drive, lockup would just not engage at all. I confirmed this with the brake light sensor which I know works because when the lockup-cycling occurs, it can be cancelled by lightly applying brake.

After a quick stop and cranking heat to max the problem disappeared and lockup worked as normal, before returning maybe 30 minutes later, but this time in the same cycling way as before.

This is what I found in the ECU. Any guesses as to severity/relevance of that capacitor leak in the top left? Could it be a culprit, and is it worth repairing regardless? Thanks.