Speed Control Surging

[PCline]

Has anyone experienced speed surges with the cruise control engaged?

I'm experiencing speed surges that can only be felt through the seat but not seen on the speedometer. They result in a change in boost of about 3 psi with a cycle time of about 5 seconds. I can only see a slight change in RPM (less than 1/4 the width of the needle). The surges occur worst with a light load on a level road. Doesn't seem to matter at what speed the cruise is set.

I have a '96 with an A/T and completely stock, except for the addition of boost and EGT gauges.

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[bluewingron]

sounds like the problem i had driving along feels like the truck slows, tach jumps up a little. dealer replaced the t. p. s. and hasent done it since.

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Ron Parker

 

[MikeR]

Sounds like your TPS sensor is acting up. Remove it and spray some contact cleaner or brake cleaner in it,re-install it and see if it does it anymore. This is only a temp fix,it will come back.

-Mike

 

[PCline]

Thanks for the tips. I'll try the contact cleaner and see if it works. If the problem comes back later at least I'll know exactly what to replace. Nothing like spending money on parts you don't need.

 

[Gary Busko]

Sounds Like the TPS. I had the same problem and removed and cleaned the sensor with electrical contact cleaner based on a reply in this forum. It is now over 3 months and almost 5000 miles with no reoccurances.

 

[Driftwood Ram]

There is something else that may cause this. I will have to do some research to find it, but I think there was a TSB about this problem. Something about "lift foot" when setting the cruse control. I had this surging the same as you described and it went away when the PCM was reflashed for another issue. May not have time to search untill next month but this could be it and not the TPS.

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96 2500 4x4 Driftwood auto DTT TC & VB Smart Controller Pac Brake Stan's 4" exhaust turbo to tail Warn 4x boards pyro,boost,trans temp on a piller, mag hytec trans pan, Reese 15k 5th wheel hitch Pulling 200 Alfa Ideal 31RL

 

[Driftwood Ram]

Ramhunter:
This is what I was talking about. Even if it is from the over valved section the basics still apply. I have a '96 service manual and it says the same thing. I tried it several times on the interstate but could never realy get the surging to go away untill the PCM reflash I have already mentioned. Hope this helps.
Topic: Cruise Control Tip
Ron Duncan
Member
Posts: 462
From:Boulder City NV
Registered: Aug 1999
posted 12-30-1999 04:00 PM
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I know this post is not entertaining like the B. O. M. B. threads but... ...
I just got my service manual and looked up speed control to see if it covered the problem I've been having with my cruise control while pulling my trailer. What it says is:
"The Speed Control has an adaptive strategy that compensates for vehicle-to-vehicle variations in speed control cable lengths. When the speed control is set with the operators foot off the excelerator pedal, the speed control thinks there is excessive cable slack and adapts. If the lift foot sets are continually used the overshoot/undershoot condition will develop. " To "unlearn" this condition you need to turn the cruise off wait ten seconds, turn it back on. This must be done 10 to 15 times while going at a steady speed (no acceleration or dedeceleration) to completely "unlearn" the overshoot/undershoot condition.
How bout that? I think I got mine real screwed up. As my frustration grows I set it a jillion different ways trying to control the **** thing as I am ramming down a hill with the hammer down and listening to my wife ***** about the magic cruise control.
I thought I would pass this along with the advise to spend the bucks and get one of these service manuals.
Ron


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96 2500 4x4 Driftwood auto DTT TC & VB Smart Controller Pac Brake Stan's 4" exhaust turbo to tail Warn 4x boards pyro,boost,trans temp on a piller, mag hytec trans pan, Reese 15k 5th wheel hitch Pulling 200 Alfa Ideal 31RL

 

[Sled Puller]

97 5 speed, When you first turn it on, it will take the pedal AWAY from your foot and race to 85. It will come back down eventually, but in Pa, I can't run 85 for 10 miles with out getting arrested.



I'll turn it on and off about three times and it will hold.



Trouble is, with the gov kit, deliv, valves, it is so throttle responsive, that the cruise is constantly throttle on/throttle off.

Ha s to be hard on things.



You guys think this may be the problem mentioned above?



Gene

 

[illflem]

My CC has always held rock steady where it's set but the throttle was constantly moving especially in a head wind. The stock cruise worked too good. I know a diesel gets best economy and longevity at a constant throttle so I modified the vacuum line to the CC servo under the battery by restricting it with a barbed 1/4" tubing coupler that I filled with glue then pushed a needle though. My CC is now much slower to react, my speed will now vary about 4 mph but my economy went up about 2 mpg, the throttle is rock steady until I hit a hill. I highly recommend this mod, it can be done in half an hour and will set you back 10¢

 

[JTBMC]

What a great post Im going to try it out right now. This mod should work on a 24 V also,will advise later.

Thanks illflem