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Discussion Starter · #1 ·
When U go to set the cruise on my Bro's truck it will usually start excelerating fairly hard and u have to hit the coast button to slow her down then sometimes it holds and sometimes it starts accelerating again. And even when u do get the cruise to actually hold at a consistent speed when u start up a hill a lot of times when the truck starts to pull down a little and starts dumping more fuel in the truck will start accelerating and continue to do so after u top the hill. The cruise control sucks so bad it is not even really usable. The truck runs fine when u drive with the pedal and there is no other issues with it. So hopefully some of you guys have heard of this issue and no what causes it. Any help would be appreciated. It is a99 cummins 5 speed. Mods include 60hp injectors and 4" exhaust.
 

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Mine has done the same thing since new. I only does it when the outside temp is under 65deg. Dealer couldn't figure it out so I just live w/ it. Cancelling and then setting speed 3-5 times sometimes fixes it.
 

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I Have Heard That The Cruise Runs Off Of Vaccum, Im Not Sure So Dont Hold Me To It, But You May Want To Look For A Vaccum Leak
 

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Does he have a fueling box on the truck? Or, just the injectors? I've heard of guys having trouble with cruise controls on heavily modded trucks; a "little fuel" isn't a "little fuel" anymore....
 

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I Have Heard That The Cruise Runs Off Of Vaccum, Im Not Sure So Dont Hold Me To It, But You May Want To Look For A Vaccum Leak
A cable and vacumn controlled servo are not used if the vehicle is equipped with a manual transmission (I think your sig says 6 speed) The speed control system is fully electroncally controlled by the ECM. Send me a PM with your email address and I will send you a PDF file on the system. Vehicle speed and distance covered are measured by the Rear Wheel Speed Sensor9 which is mounted to the rear axle. A signal is sent from the RWSS to the Controller Antilock Brake (CAB) computer. A signal is then sent form the CAB to the ECM to determine speed. The ECM will then determine strategies for the speed control system operation. I know that sounds like a lot, but your problem might be associated with a bad ground on any or each of the aforementioned modules
 

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mine has done the exact same thing . was thinking about changing the servo controller . mine is a auto.
 

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Discussion Starter · #7 ·
A cable and vacumn controlled servo are not used if the vehicle is equipped with a manual transmission (I think your sig says 6 speed) The speed control system is fully electroncally controlled by the ECM. Send me a PM with your email address and I will send you a PDF file on the system. Vehicle speed and distance covered are measured by the Rear Wheel Speed Sensor9 which is mounted to the rear axle. A signal is sent from the RWSS to the Controller Antilock Brake (CAB) computer. A signal is then sent form the CAB to the ECM to determine speed. The ECM will then determine strategies for the speed control system operation. I know that sounds like a lot, but your problem might be associated with a bad ground on any or each of the aforementioned modules
Sorry for the confusion the truck that has the problem is a 99 with a 5 speed. No chip/programer, only 60hp injectors. I sent the pm and I would appreciate the diagram u were talking about. Thanks
 

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Mine does it too. Just wants to keep goin faster and faster.
 
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