cruise control on a plym voyager

[James]

I have a prestige (javascript:adds(""
Roll Eyes) 1990 plymouth voyager LE with 3.3 V6 and computerized auto trans.
Cruise control gradually faded away - was stop-start for about a year until finally died. At the end it was actually speeding up by itself sometimes, which is obviously very undesirable.
I am wondering if anyone has experience with these models and could suggest what usually goes wrong with the cruise control. I am fairly confident it is not the power unit itself due to the way it faded out - seemed more like a loose connection but could be the speed sensor I suppose which would be nice and simple. Any other suggestions?

thanks

[DanD]

It’s not likely the speed sensor the same sensor supplies info for transmission and the speedometer.
I’ve changed a few cruise switches and the customers compliant were kind of the same that the car would speed up all on its own.
I don’t mean to say that this is what’s wrong with yours, because there are quite a few tests that can be preformed on the system.
To do the tests you would need a scan tool to access the engine controller to a multi meter to perform pin checks.
Sorry that I’m not more of help here, but maybe one of the others can shed some light on this.
Dan.

[James]

By cruise switch you mean the one on the steering column?
I'd be a bit surprised if that was it, due to the nature of the way it faded out and that fiddling with the switch never seemed to make any difference.
I since happened to find a thread started by someone else on another forum for an 89, and was surprised to find that you can get computer fault codes just by switching the ignition thus: on > off > on > off > on within 5 seconds. The dash fault light then blinks out the fault codes, and you can look them up. Here is the link:

www.allpar.com/fix/80s-codes.html
I got a 15 which means speed sensor. A poster explained that if it is not working, the trans or torque conv will not lock in at about 45 mph (whatever that means) but trannie will still work (probably not as efficiently I'd guess). Also I have a separate mechanical speedo cable.
I will replace the speed sensor but won't be convinced until I see it actually working.... I'll report back if I get around to it and don't lose this website.

PS having made a previous cynical remark about my voyager, I have to say it has been a great vehicle - it may even start to look slightly stylish in a few more years if it lasts that long. I know they have weak trannies which I had to replace once, but now I don't floor it very often at all, just nurse it along so hopefully it will last many years. I still sit on 80 on the turnpike sometimes however when in a hurry - hopefully hard accelleration is the bad thing..

[DanD]

James to tell you the truth I forgot all about that the older ones still used a cable.
So you’re probably right about the speed sensor being the problem.
Sorry I didn’t do my homework before I posted.
I was thinking that with a scanner I would be able to go through and do a few actuator tests and usually see who wasn’t doing their job.
So make sure you come back, it would be good to have more people like yourself here on the board. You certainly know how to do research.
Dan.

[James]

Excellente, I just replaced the speed sensor (mine was about $55 from Napa since it is combo electronic and mechanical, but elec only jobs are only about $25) and it works perfectly now. NOw for big trip NJ to Florida and back....
I can add another diagnostic symptom to the picture: when the problem was still intermittent, the car was shuddering and shaking as it passed through the 40-50 speed range - due no doubt to the clutch lockup trying to activate as the speed control spat out sporadic signal. I thought it was something like a front end or mounting problem but that is fixed now too. I don't think this would happen with every case of speed sensor failure, but could be useful supporting evidence in some cases.