KZJ78 Auto won't Lock up in 4th

[Henry]

Hi

My Auto will occasionally not stay locked up in 4th. It happens on the open road and if I turn the o/Drive off/on a couple of Times it will lock up again.

The Auto is warm but not over hot.
It was rebuilt 2 years ago after water was in it. The fluid level is good and not burnt or dirty... I had the ECU Capacitors done 2 or 3 years ago...

Any ideas?

Henry

[Gardengnome]

I have had this recently also. I have also had an elevated engine temp issue on inclines to boot. Last time I noticed that the the auto lock-up was not working after a climb with the temp raised. Still no lock up for a period after the hill with temp dropping and then it locked up once engine temp had dropped back to normal. Never had a problem before the temp rising issue.

I'm still running radiator trans cooler with no external. So I'm assuming if the temp rises the auto disengages the Lock-up clutch.

I'm doing a full coolant system service and external trans cooler so will see what the outcome is for lock-up after this.

Keen to hear what others have to say.

Cheers, GG.

[Henry]

Hi Gardengnome

In your case the High Engine Temp will have caused the ECU to not lock the torque Converter.

I am still chasing my issue....

[kbushnz]

As the auto is ECU controlled....
The Lock up is looking for a few things....
Water temp is hot enough.

And also things like speed, revs, TPS etc etc...

The lock up is driven by a solenoid in the auto....

You could have any number of issues...
The most common is the ECU starting to play up due to corroded boards and leaky caps.
Next could be a sticky solenoid or a loose wire to it...
Then there could be a faulty temp sender unit... There are two... one for the gauge and one for the ECU.
A faulty sender or other sensor should pop up an error code...As the ECU used these for engine control also...

Good luck....

Calvin