# Surging Cruise Control



## jblackburn (Apr 14, 2012)

6AT or 6MT? 

Have you adjusted plug gaps or do you run anything besides 87 octane?

I've never had this happen in the Cruze (mine's a manual), but my old Camry was a total idiot on cruise control when it got to a hill and did something similar to what you're describing if it couldn't maintain a speed constantly on the gas pedal.


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## montess1 (Oct 13, 2012)

No on the plug gaps,I only use Shell 93 octane.It totally goes away when the cruise is off so I don't think it's the plugs.Seems like a problem with the cruise.


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## obermd (Mar 3, 2012)

Since it only happens when descending, it could also be DFCO engaging and disengaging. There can be a slight surge when DFCO disengages.


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## alyupe11 (Jun 9, 2013)

6mt and no issues noticed.....


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## jblackburn (Apr 14, 2012)

I'm thinking its just being too sensitive. Maybe you are going from accelerating to not to DFCO and then back to accelerating. That will create a lot of jerking. 

The Cruzes cruise control is actually one of the better ones ive used - at least on the manual (the auto liked to drop gears easily). If you're going down a hill and then start going up another, and have it set at 60, as soon as it notices you losing speed from 65 or so, it will hit the gas again. Very smart. My Camry/Volvo would wait til it hit 60 again, already on the hill, be too slow hitting the gas, downshift to 3500 RPM, speed up, and then hold that gear for a while. So annoying. 

If you want to take it in to the dealer, it would be worth giving them a call first. But I'm sure you'll just get the "cannot duplicate". Practice with it, find somewhere you can get the car to do it, and then take it in and ask a tech to go for a drive with you. 


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## montess1 (Oct 13, 2012)

Mine is the 1.4 auto. I need to take it any way sometime soon as it has the problem with the transmission when at a stop it almost feels like you get bumped in the rear,this goes away if you put it in manual shift mode and poor a/c performance.It takes over 12 miles before it cools the car down.


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## rmass09 (Apr 17, 2011)

My last car used to do this and my '13 cruze does this but its not as noticeable as my previous


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## spacedout (Dec 7, 2010)

On downhills the car has no compression braking to speak of so the car will gain speed from what you are set at. Once you gain 3+MPH the car attempts to slow you by downshifting to 5th. however on anything more than a slight grade this doesn't help much. 

I think obermd is correct about the DFCO, I have noticed the automatic with cruise set seems to come out of DFCO on downhills every 8-15seconds and behaves like you said. Coast down the same hill with the cruise off it does not do it. Its very slight feeling but strange since the grade and speed have not changed. So my question is now have any of you manual transmission guys noticed on long downhill grades the car coming out of DFCO with the cruise set every 8-15seconds?


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## spacedout (Dec 7, 2010)

jblackburn said:


> The Cruzes cruise control is actually one of the better ones ive used - at least on the manual (the auto liked to drop gears easily). If you're going down a hill and then start going up another, and have it set at 60, as soon as it notices you losing speed from 65 or so, it will hit the gas again. Very smart.


This is exactly how the automatic works in manual mode. If I leave the car in M6 downhill and gain 5-10MPH above your set speed as soon as the grade changes to uphill again even though my set speed is still lower than what I'm going you feel the car getting onto the gas. 

There is also no hunting for gears on uphill grades, even if it levels out a bit. Once the car downshifts to 5th it will hold that gear all the way to the crest of the hill. has to be some sort of angle/tip senor on the car to sense the grade so well. I agree its one of the best cruise controls I have used.


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## jblackburn (Apr 14, 2012)

Long downhills? Nope. It tends to speed up too much. The MT has no compression braking whatsoever.

On slight downgrades I can feel it on and off the gas but you have to be paying a lot of attention to it to notice it. 


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## spacedout (Dec 7, 2010)

With the automatic & cruise set the car is in full DFCO going downhill and all of a sudden acts like I hit the gas(foot is off the pedal) for sec, then goes back into DFCO a few seconds later. it repeats this cycle all the way down the grade, like I said about once every 8-15seconds. 

Its almost as if the cruise doesn't think you should be coasting for so long and has to check to make sure it doesn't need gas. The weird part it behaves this way even when your above your set speed.


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## XtremeAaron (Jan 22, 2012)

This thread is interesting as I have the 6AT and use the cruise control every day and don't think I have noticed this. I'll pay more attention and report back.


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## H3LLON3ARTH (Dec 16, 2011)

spacedout said:


> With the automatic & cruise set the car is in full DFCO going downhill and all of a sudden acts like I hit the gas(foot is off the pedal) for sec, then goes back into DFCO a few seconds later. it repeats this cycle all the way down the grade, like I said about once every 8-15seconds.
> 
> Its almost as if the cruise doesn't think you should be coasting for so long and has to check to make sure it doesn't need gas. The weird part it behaves this way even when your above your set speed.


I felt this in my 6MT traveling threw Missouri it felt the same way like the gas kicked in just for a second 6th gear cruise set at 63mph

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## NickD (Dec 10, 2011)

Trying to make me even happier I have the manual transmission? Best cruise control I have ever had. Love that DIC display, can set my speed to the exact number. Even on steep WI hills, holds dead steady in sixth gear, going up or down.


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## montess1 (Oct 13, 2012)

spacedout said:


> On downhills the car has no compression braking to speak of so the car will gain speed from what you are set at. Once you gain 3+MPH the car attempts to slow you by downshifting to 5th. however on anything more than a slight grade this doesn't help much.
> 
> I think obermd is correct about the DFCO, I have noticed the automatic with cruise set seems to come out of DFCO on downhills every 8-15seconds and behaves like you said. Coast down the same hill with the cruise off it does not do it. Its very slight feeling but strange since the grade and speed have not changed. So my question is now have any of you manual transmission guys noticed on long downhill grades the car coming out of DFCO with the cruise set every 8-15seconds?


Mine was doing the surging about once per second,a fast repetition till off the down hill slope.


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## tmlferguson (Mar 28, 2013)

I know exactly what you're talking about...

http://www.cruzetalk.com/forum/34-1-4l-turbo/14340-cruise-cruze-control-pulsing.html

I assume it's the car just trying to maintain the set speed going down the hill... if you watch closely, you can even see the RPM bounce on the guage...

I've not had a chance yet to datalog and send in for diagnostics.
Are you tuned or stock?

I also experienced the same issue that you described while being stopped... Almost feels like you've been tapped from behind. I thought that had more to do with the brakes then the transmission though...

Let me know how you make out at your dealer.


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## tmlferguson (Mar 28, 2013)

By the way, what does DFCO stand for?? :blush:


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## grs1961 (Oct 23, 2012)

DFCO - Delivered Fuel Cut Off - it's described in the handbook (well, it is in mine).


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## NickD (Dec 10, 2011)

Yeah, the instant miles per gallon jumps up to 99, seems like it should be greater than that.


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## spacedout (Dec 7, 2010)

Going down some pretty steep hills yesterday I could not get it to do this surging at all with the cruise set. I'm guessing there must be some other variable like AC use(I was not using my AC).


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## tmlferguson (Mar 28, 2013)

It's not related to AC as mine does it with or without the AC engaged.


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## montess1 (Oct 13, 2012)

tmlferguson said:


> I know exactly what you're talking about...
> 
> http://www.cruzetalk.com/forum/34-1-4l-turbo/14340-cruise-cruze-control-pulsing.html
> 
> ...


Mine is all stock,I think a service bulletin is out for the clutches in the auto for the bumping issue.I did notice the tach jumping also.


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## obermd (Mar 3, 2012)

NickD said:


> Yeah, the instant miles per gallon jumps up to 99, seems like it should be greater than that.


If you put your Cruze in Metric DFCO is easily identified as 0.0 L/100KM. 99 MPG is as high as the car can display, but this can be anywhere from no fuel to 2.3 L/100 KM.


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## obermd (Mar 3, 2012)

While driving across country this weekend I was able to get my ECO MT to surge going down hill. It was very definitely the car going in and out of DFCO as the hill and speed were right at the point where aero drag would slow the car down just enough to reengage the injectors to maintain the cruise control set speed and then the car would accelerate just enough to be able to start coasting again. If I hadn't been looking for this I probably would not have noticed.


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## Chevy Customer Care (Oct 29, 2011)

montess1, 

We would agree wholeheartedly with jblackburn's suggestion early on in the thread - make sure that you can easily duplicate this before you go into the dealership to get it checked into, if you decide to go this route. 

Keep us posted with any results!

Sarah (Assisting Jackie)
Chevrolet Customer Care


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## tmlferguson (Mar 28, 2013)

It's not something that happens all the time... It's very intermittent and spontanious on hills... If it could be duplicated at will, it most likely would have been dealt with already.

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## montess1 (Oct 13, 2012)

Chevy Customer Service said:


> montess1,
> 
> We would agree wholeheartedly with jblackburn's suggestion early on in the thread - make sure that you can easily duplicate this before you go into the dealership to get it checked into, if you decide to go this route.
> 
> ...


I might have to go back up north to a dealer where this can be done easily.Not any hills around this area.But the bumping can be felt at just about any stop light.


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## NickD (Dec 10, 2011)

With the older vacuum operated systems, the stop could be adjusted and had to, so the cable from the modulator to the throttle was in the proper servo range. And could also limit the maximum pull on that cable so the cruise control was not over controlling. This would prevent surging.

But what can you do with a firmware controlled microcontroller when you don't even have the source code. Would take years to convert that machine code into source code.

Guess all you can do is to see your dealer.


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## tmlferguson (Mar 28, 2013)

@montess1
Did you take the cruze to the dealer? Any satisfaction? What did they say or do?

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## jmurf (Mar 25, 2013)

Mine is doing it too!! I have several nice hills around my dealership to try it on. Please keep us posted if anyone finds anything out and I will do the same


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## k8busa (Apr 12, 2013)

My 2013 1.4t auto has done it since day one. Cruise set going down hills it surges. Depending on the hill grade it gets worse, you can see the tack jump up and down, feel it and see it. It was most noticeable this past weekend when i had the car loaded traveling with more weight going down hills. Not sure if its something i need to be worried about but being that its a new car it drives me nutz !!!


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## obermd (Mar 3, 2012)

This is the car going in and out of DFCO. Switch your car to Metric and watch the "instant" MPG value to see DFCO, displayed as 0L/100KM. There will be a small "reverse" surge when entering DFCO and a larger one when leaving DFCO. The surges correspond to the fuel injectors being turned off and then back on.


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## montess1 (Oct 13, 2012)

tmlferguson said:


> @montess1
> Did you take the cruze to the dealer? Any satisfaction? What did they say or do?
> 
> Sent from my Samsung Galaxy Siii via AutoGuide App


Sorry it took so long to get back,I have not had time to take it in yet but still having the problems.


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## obermd (Mar 3, 2012)

montess1, how strong are the surges? Light surges are normal. Strong ones aren't.


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