cruse control wooes

[bigwhitedog]

I have an early 07 and on down grades the cruise control hammers. It's so bad that I have taken to turning it off on down grades. The dealer says nothings wrong, but there is something going on.



Has anyone else experienced this? if so what was the cause?

 

[MTaishoff]

Mine surges on cruise control; going downhill only. It must be a common issue as there are other threads here on the same subject. Truck runs great otherwise and no trouble codes, so I've just learned to live with it...

 

[Prairie Dog]

Weird, mine works flawlessly.

 

[AH64ID]

Mine does it on one specific grade, and is smooth as glass on the other. .



I think some folks contribute it to injectors.

 

[cerberusiam]

I have an early 07 and on down grades the cruise control hammers.

I have no idea that that means. A little more succinct description of the problem might help.



CC can get weird depending on mods. Mine works great except for the fact it won't cancel correctly under heavy uphill acceleration, sometimes.

 

[mwilson]

Mine will flip out and buck like crazy if you have your foot resting on the throttle at all with the cruise engaged going downhill.

I wonder if that is what is happening with some of the members that are having issues.





If your foot is on the floorboard where it belongs when the system is in use the truck will occasionally hitch a little going downhill with the cruise engaged, has always done it.



Mike.

 

[HBarlow]

I think it is common with all Rams. All three of the ones I have owned will surge just enough to feel on some unloaded downgrades. I think it happens because the ECM programming is not able to transition back and forth between fueling and no fueling so precisely that the driver cannot feel it. I've only experienced it a few time in almost 10 years and 650k miles of motoring pleasure so consider it no big deal.

That is one of the many little tiny issues that dealer service departments have no idea what the owner is talking about, can't duplicate it, and can only tell you "it is normal, they all do it. " In this case, they all do it.

 

[AH64ID]

I think it is common with all Rams. All three of the ones I have owned will surge just enough to feel on some unloaded downgrades. I think it happens because the ECM programming is not able to transition back and forth between fueling and no fueling so precisely that the driver cannot feel it.

That's exactly what it feels like in my truck. In the right circumstances you will be on a hill that is just the right incline that no fuel is too little, and min fuel it too much.

 

[mwilson]

I finally remembered to mention this..... have been planning to bring it up for a couple of months... ... .....



I experienced the downhill cruise surge several times in the Cascadia Road Tractor with a 60 series Detroit Diesel that I brought back from New Mexico.

Also have experienced it in one of my M2 delivery trucks equipped with a 900 series Mercedes engine.



I think that the engine management system is doing exactly what Harvey has mentioned, the ECM can't quite figure out what to do or when to do it in certain downhill conditions.



As I said above, if it is a violent buck and surge make sure your foot is not resting on the throttle pedal because the ECM is going to try harder to compensate for the fuel you are adding to the equation.....



Mike.

 

[AH64ID]

Things like larger injectors and modules or tuners will also amplify the issue.

 

[SDrake]

Does this system operate strictly through electronics or is there the old actuator operating through linkage or cable to operate the mechanical input the accelerator pedal uses? If there is a linkage involved, then varying friction in the linkage will give varying results. for it to work smoothly with out surges the friction has to be at a minimum. The amount of input required to move the linkage mught be too much after the linkage actually moves so then the controoller has to back off and then you have the cycling effect. Forgotten all my control theory terminology, but do remember that the smoother the linkage the better chance you have of it working as disired. Any stickiness in the linkage will aggrevate a too much too little situation.



I just moved up to a 2003 from a 94. Haven't looked at the cruise setup yet. Mine does not work because the speedometer quit right after going through a car wash a few days after I bought the truck. I am working on that problem right now. Think I have got it narrowed down to the ECM connector. Need to figure out what to do about it.

 

[AH64ID]

07 is strictly electronic.

 

[mwilson]

'06 and up are drive by wire, no cables or linkage.



Mike.

 

[AH64ID]

'06 and up are drive by wire, no cables or linkage.



Mike.

05+ actually.

 

[steved]

I for one had this without a single mod done to the truck... it was caused (in my instance) by worn or leaky injectors. Once replaced, my cruise is flawless... uphill, downhill, loaded or empty; it is smooth as glass. There was no other change from before to after... the injectors were simply replaced with Flux Is, and my cruise surge was gone.

I added a SmartyJR later, and it had absolutely no affect on the cruise...

My feelings is that the leaking injectors won't allow the ECM to maintain a proper rail pressure, or in other words; the leaky injectors bleed off pressure to fast for the ECM to compensate.

For what its worth, I added cruise to an ST truck... so the surging was "normal" and there upon installation. It was violent at times... and injectors fixed it.

 

[Prairie Dog]

All common rail are drive by wire - 03 and up.

 

[AH64ID]

But 03-04 all have an engine bay APPS, and a vacuum pump and crusie control. . There is still a throttle cable on them, the 05+ have no throttle cable or cruise control module.

 

[mwilson]

I didn't realize that the '05's were completely by wire. I have a gap in my hands on experience with the 03-05 trucks. Have owned or currently own both older and newer trucks but never that vintage.



Mike.

 

[steved]

I thought the APPS was an auto-only thing in the earlier trucks... the reason I was able to simply add two $30 switches and gain cruise control?? I have a manual.

 

[cerberusiam]

These trucks have been drive by wire since the VP pump was introduced in 98. 5 and the they all have an APPS to control the fueling. The APPS does a bit more than the old 2 wire TPS. IN MY 05 the CC and trans TV control was moved into the ECU and the APPS moved to the inside of the firewall out of the engine compartment.



CC on the 05+ models is all in the ECU, before that it was a combination of vacuum and electric servo depending on the style.



Using the accelerator with the CC is engaged guarantees some weird behaviour. The ECU is not smart enough to figure out what to do with 2 inputs that doesn't match its preprogrammed ranges and it freaks momentarily. It really is not that intelligent. :-laf



Injectors and fueling mods tend to confuse things even more beacuse the ECU can't handle the chnages to fueling curves. Normally its little bumps but sometimes it glitches worse. Mine will give a couple small adjustment surge when the fueling is SW5 or more on Smarty otherwise its steady as long as I don't touch the pedal.



Different trucks just seem to react differently to the inputs and there is really no common theme as to why. Electronics, its the new wave.