Engine/Transmission (1994 - 1998) cruise control goes wild

[DrJC]

The cruise control on my '96, 2500, 4x4, Cummins diesel, 5 speed sometimes holds the speed just as set and at other times will self-accelerate beyond the set speed by as much as 15 mph. Usually, it will slowly return to the set speed but then do another hard acceleration past the set speed when going up a grade, including an overpass.



I've noted that this seems to be directly related to outside temperature: At about 70 F, the cruise control works perfectly; as the outside temp decreases, the glitches increase proportionately. For example, yesterday at about 35 F, I set the cruise at 60 mph and the vehicle hard-accelerated up to 75! I tapped the brake to disengage.



Any suggestions, guys (and gals)?



Dr JC



P. S. Please lay off the "lazy foot" stuff--that's just DC-speak for we've got a bad design in our product and we'll blame the consumer. I'm very careful with my foot position when setting the cruise control.

 

[Boldt's Wagon]

I have had the same thing happen to me. OK one day and the next day it takes off, turn the cruise off, then on again, and then it is OK. ????



I also have the radio coming on claiming it has a tape in it and trying to reverse the non-tape direction - have to eject the nonexistent tape.

 

[LHastings]

My 98 auto does the same thing when it is cold. If I wait until the Engine is good and warm and the engine compartment is warmed up also, it seems to not do it.

Does the cruise control servo under the battery has any electronic in it that could have a cold nature problem?

 

[illflem]

Sounds like you guys either have bad PCMs or the connections to it are corroded.

 

[Dennis Garrett]

Mine did some goofey things when the cable frayed, It would jerk & tug at the cable trying to maintain speed, then the cable would give, & accelerate. Might look it over, it frayed at the pump end, close to the ball, or lead thing on the end. It kept trying to pull the fray back into the cable housing. It wasn't too bad to replace, had to take the driver's side battery & tray out, that was the worst part.

 

[BWilson]

Don't know if this helps or not but mine was having trouble keeping speed going up and down. Someone in the forum told me to retrain the computer by setting the cruise and as soon as it took the pedal turn it off. Repeat this step 10 to 15 times. For me it took more than 15, probably closer to 50 but it happened on my truck and I quit using the cruise altogether for a year or so until I read that.

Works great now!!

 

[Andy Redmond]

For curosity, pull a vac. line connection on the firewall, so you see oil film?



If so you have a bad ck. valve on the vac. pump that has allowed the engine oil to contaminate the vac. sys.



There are TSB's and some potential help from DC on this one.



The other post listed good troubleshooting too. Get a FSM and bone up on your diag.



Good luck

Andy

 

[Wirenut]

My '93 and my '97 both have done this. You set the cruise and you get put back in the seat and the people behind left in the black smoke! Kinda scary. My cruise also will not work under 32 degrees I guess its supposed to work like that?

 

[GeneralMachine]

cruse control

My 97 was acting just as you desribed, I recived a letter from the stealer, they have had a recall on the trottle, they replaced all the liknage, and also the spring's, now the cruse is steady as a rock. hope this helped Harv

 

[Ncostello]

Not a 12V but my 99 does this also. I've tried to re-calibrate by setting while crusing and then turning off. Maybe 50-75 times but it just dont work for me. And sometimes it works fine first time. Other times it goes from 55 to 75 mph. Maybe just 55-60 other times.



Once while playing with it early one morning on the highway to avoid the state police, it went from 55 to 65 and I was just letting it take its course. Whammo... state police comes over the hilltop and I tried to hit OFF but hit SET again which sent the thing into what felt like full throttle up towards 70mph. I tapped the brakes but found out my brake light switch isn't working properly... I guess... cause just a tap didn't work... you have to really press them to get the brake light to come on. Under power, the brakes dont hold this thing back at all. Guess I better get that switch adjusted or replaced too!! For now, I'm just letting it go... I've got other problems with the truck that need my attention (idle miss... which also seems intermittant).

 

[Deezul1]

My 97 does that also. Not all the time but when it does the off/on thing will fix it. Some times it takes 3-7 times for it to settle down and others it works ok after 1 time and other times it works fine 1st time out which is why I dont think its a bad connection but who knows for sure?

 

[Ncostello]

The only real problem I have is that it never works right when my knee is hurting from driving for a long time. But it will always work when I dont need it. I've noticed it seems to work almost all the time as long as my speed is 50mph or below. Hmmm.