Cruise Control

[jeisbell]

My recently purchased 94 sport has 156K and is in need of some tlc...one thing I can't figure out is a surging when the cruise control is used.
It accelerates, then coasts......
Also, during normal driving, my speedo needle bounces. Are these related?
Do they operate on a vacuum system?
Thanks!

 

[MrShorty]

Yes, the cruise control is vacuum actuated. I think the CC system uses the input from the vehicle speed sensor (t-case/tranny end of speedo cable) to know the set speed. It sounds like there may be a problem with the VSS. Does the surge/coast seem to be in sync with the speedometer bounce?

 

[Harry5150]

Does it surge when flat/uphill/downhil?

Mine has always accelerated going uphill (my fiance's 98 mustang does this too) and has recently started pulsing when going on a long downhill stretch. When I put my foot on the pedel, I can feel it going up & down & then I have to turn the cruise off. No speedo bounce though.

 

[RealXP8]

Jeisbell, my mustang does the same thing, in 5 mph increments. Be sure to post the cure if you find one.

 

[Shurup]

I believe that small changes in speed as well as gas pedal going up and down are normal. All the cars I had acted the same way when cruising.

 

[RealXP8]

In my case 5 mph up and then down is alot, not to mention it accelerates hard. Normal cruise control does 1 maybe 2 mph to regulate for inclines and declines. Imagine putting your foot to the floor and then letting off. If jeisbell is experiencing this, like me, It makes the cruise control useless, you'll get car sick.

 

[Crankcase]

My Dads 94 used to do that too...Say the set speed is 50, and you are cruising...the X lets off the gas until it goes below 50, realises it is not going 50, hits the gas hard, until the X is above 50,the it thinks it is too fast, so then repeats the slowing down satge....

I think the taillight resitance has something to do with this.....Check to see if any bulbs are burnt out.....