NEED HELP - Intermittent Cruise Control & TQ Conv Lockup

[TurboJunky]

Got a real doozie here.

My car's possessed! My cruise control and torque converter lockup seem to go out simultaneously. Occasionally I notice the torque converter will lockup on its own when it's supposed to and when it does my cruise control will work (albeit not correctly). When my torque converter fails to lockup my cruise control won't engage. It's as if they're both tied in with one another somehow and when one works, the other works and when one fails to work the other fails as well. I can manually lockup my torque converter at will so I know that's operating. Also, when the cruise control does work it won't maintain speed. It will quickly accelerate the car, the let off the throttle, then accelerate again quite abruptly, then let off. It's as if it has a mind of its own. There are times when the cruise will maintain speed and it will simply stop functioning and disengage, then the torque converter won't lockup unless I manually engage it. My car does have the VDO GNx dash if that has any relevancy.

Is the cruise control in any way associated with the torque converter lockup function??

ANY IDEAS??

 

[v6turbo87]

The 2 are not tied together electrically so activating one should not affect the other. However both ARE disengaged by switches located above the brake pedal. Take a look at the switches at the brake pedal. Any switch you see needs to be fully pressed against the brake pedal. As far as the intermittent issues with the cruise control, the wiring from the blinker stalk down through the steering column is prone to getting chafed. It is small gauge wire an can break with age or become intermittent. Check the wiring. You can get a new stalk if need. It just pulls out of the column with a good hard tug on it.

 

[EVIL]

By chance, do you have a 145 speedo with a reducer installed on the speedo wire under the hood?

D

 

[TurboJunky]

The 2 are not tied together electrically so activating one should not affect the other. However both ARE disengaged by switches located above the brake pedal. Take a look at the switches at the brake pedal. Any switch you see needs to be fully pressed against the brake pedal. As far as the intermittent issues with the cruise control, the wiring from the blinker stalk down through the steering column is prone to getting chafed. It is small gauge wire an can break with age or become intermittent. Check the wiring. You can get a new stalk if need. It just pulls out of the column with a good hard tug on it.

I know the brake light switch is working properly if that's one you're referring to.

Would a chafed wire cause the cruise control to remain ON but cause the car to accelerate, then decelerate and back and forth?

 

[TurboJunky]

By chance, do you have a 145 speedo with a reducer installed on the speedo wire under the hood?

D

The original owner installed the GNx style dash and it has the 160mph speedo. I know it has a separate cable extending from the dash down and into the transmission for the speedo.

 

[v6turbo87]

There are separate switches for the cruise control and TCC lock up. Double check all switches on the brake pedal.
Yes damaged wiring could cause the issues you are having. Pull the stalk out and inspect the wiring that runs down the steering column and into the cruise control module undet the dash.

 

[RmvBfrFlght]

What v6turbo87 says... There are two switch assemblies activated by the brake peal.

One has a vacuum hose on it that releases the cruise control (CC), with the electrical switch on that assembly releasing the TCC (via +12 v power being interrupted). This is most likely the switch that isn't adjusted properly. As both CC and TCC lockup would both be lost at the same time. Since it doesn't tell the CC to disengage, just releases the servo vacuum, the CC would be releasing on and off.

The other switch assembly has two electrical switches in it. One turns on the rear brakes lights, with the other turning off the CC.

Confusing way to set up the switches, but that is how they are.

RemoveBeforeFlight

 

[1KWIKSIX]

The original owner installed the GNx style dash and it has the 160mph speedo. I know it has a separate cable extending from the dash down and into the transmission for the speedo.

Can you post a picture of your dash set up for us? It may be helpful .

 

[TurboJunky]

Here's what I have on file.

 

[1KWIKSIX]

Looks like it's an AVC dash. These utilized VDO gauges (and a mechanical speedometer). Could also be a Performance Instruments Dash, I may be mistaken, but it sure looks like the AVC GNX style dash to me.

FYI....here's a copy of the AVC dash installation instructions and wiring details. It may be helpful for you.

Dave

 

[TurboJunky]

Dave,
Thanks for the info and it does have VDO gauges. I know nothing about the dash other than the original owner whom I bought the car from did the work.

After I posted this I continued to drive and about 10% of the time the cruise control and TQ lockup would work in concert with each other. On the flip side of the coin they'd both simultaneously stop working. Without a doubt they're both tied in with one another somehow.
- Dean

 

[GNVenom]

Cruise control and TCC lockup are related; they're both governed by the VSS. If you lose the VSS signal, the trans will unlock and the cruise will stop working. Additionally, the SES lamp will turn on with a code indicating VSS failure.

One of the biggest problems with the dash conversions is the lack of VSS signal or intermittent signal. Check to see if the VSS is wired in, using the VSS Buffer, or does it have its own VSS transducer in the speedometer cable?

 

[TurboJunky]

Cruise control and TCC lockup are related; they're both governed by the VSS. If you lose the VSS signal, the trans will unlock and the cruise will stop working. Additionally, the SES lamp will turn on with a code indicating VSS failure.

One of the biggest problems with the dash conversions is the lack of VSS signal or intermittent signal. Check to see if the VSS is wired in, using the VSS Buffer, or does it have its own VSS transducer in the speedometer cable?

John,

Thanks for confirming what I've been experiencing with this car since I've owned it. Problem is I didn't do any of the work and know virtually nothing about electronics. I've owned these cars since 1990 but they've primarily been stock garage queens and this is the most modified TR I've had and it's been a nightmare with Mickey-Mouse problems. What's a VSS signal?

 

[GNVenom]

Vehicle
Speed
Sensor

Look up VSS buffer. It's a green box with two connectors on one end and an optical pickup on the other (or in your case, probably two wires).