Torque Converter Cycles from Lock to Unlock @ Highway Speed


May 24, 2001
I posted this a few months ago. It still does it. Not always. Maybe 3 out of 5 times I cruise down the highway. If I lock it manually with my toggle switch. It stays in fine. Everyone said it was a ground problem. I'm now out of ideas. My Direct Scan shows it cycling like crazy also. I've tried most everything related to locking the converter....I cleaned the three ground wires linking the computer to the back of the motor, I added grounds inside the car to those same wires. I added engine to chassis grounds, cleaned the battery to engine ground, added body to engine and body to frame grounds. I replaced the MAP sensor, T/P sensor, MAF sensor, And Vehicle Speed sensor. About the only one left is the coolant temp sensor! I've even change the computer. I wish I had another chip to try. Although, I wouldn't think it would be intemittent because of the chip. I'm out of ideas.:mad: Any suggestions would be appreciated. If you need more info, let me know. All of this started after the first engine rebuild and installation. Dave C.
Ck the tcc/cruise switch at the pedal. Sounds like with vibration it may be right on the verge of opening and a slight bump would kick it out as you describe..

Worth a look.

I tried pulling back on the brake pedal when it acts up, and it doesn't bother the cruise control at all. I'll pick up a switch at the salvage yard. Thanks. Dave C.
TCC cycling

Check if the third and 4th gear inputs are 'cycling'
in your DS file, that'll make the ECM drop the TCC out.

What chip are you using?

I assume the vehicle speed displayed on DS is ~stable....

I don't know much about tcc but...

I really have no experience with these type of things but I had an 84 cutlass with the 231 and mine did the exact same thing. Turned out to be the temp sensor wires. They had dried up and cracked. The exposed wires would cross and the tcc would lock and unlock accordingly.
Thanks, I'll check the wires. There are 3 temp sensors. I know the one with the flat blade connector is the one for the idiot light. Which one of the other 2 would control the computer cycling the torque converter? One has one wire, the other has 2 wires. Dave C.
I found it!!! I've put up with this for 3 years now! It has gotten worse. I dropped the pan to remove my tranny brake and found a bolt lying there. It was the short bolt that holds the divider plate just behind the valve body. I guess I can thank the local speed shop for the great install they did.:rolleyes: It must have been finger tight and eventually loosened and fell out. It probably allowed pressure to bleed off going to the nearby 3rd/4th gear switches. Just like TurboBob suggested.;) Thanks. Dave C.