Cruise Control Fluctuations

[Max Torque]

The cruise control on 2000 Golf TDI with automatic transmission has been unsteady since day one. My dealer suggests to reprogram “the computer”. Will this affect the Upsoluted portion of my ECU? Is the cruise control computer actually inside the ECU?

When I say the cruise control is unsteady, I mean that it waries the power constantly, while still keeping the speed right on. I can feel the power increasing and decreasing constantly, about once every second. It feels a bit like riding a rocking chair. At lower speeds, around 45-50 mph where the transmission is not in lock, the RPM gage moves +/- 100 RPM in time with the power changes. At highway speeds with the transmission locked up I can still feel the slight power fluctuations, but they don’t show on the RPM gage.

Good fuel economy needs a steady foot. This crusie control could be responsible for my not spectacular highway mileage.

Any suggestions? The car is going in for the 15,000 KM service soon.

Max

 

[george cumber]

A thread was posted a couple of weeks ago
about cc I cant find the link (sorry).
The on/off switch has ben known to cause
problems if it is stuck between contacts,
try swithing off then back on.
hope this helps.

------------------
Indigo blue 5 door Golf Mk 4 GT TDI simply the best!! Compression Ignition Rules !!!
Citroen ZX TD 5 door hatch

 

[The Ripster]

99.5 has done this since day one. At higher speeds 70mph plus it is not so noticeable.
Don't know what can be done, I just don't use it much below 65mph. Dealer has been no help, and neither has VW.

 

[Marissa]

You have hit it on the head! This is the exact same problem I notice on my Auto Golf 2000 too. I've taken it in before going over the 24Kmile mark and they told me it had a 50rpm resolution. Sounded like horse sh*t to me. I agree with a previous post, it is much less noticeablt at high speeds when the throttle is much more depressed. I really notice it with cruise control on at about 40-45mph when on a flat road. The car lurches back anf forth. You can actually feel the car accellerate and decellerate like someone is tapping on the pedal exactly as you have posted.

Please let me know when you find out the problem.

[This message has been edited by Marissa (edited March 12, 2001).]

 

[Al Kane]

My 2000 Jetta 5 spd doesn't do this at all; it's rock steady.

Cruise control works in a feedback loop. I once had an aftermarket cruise control on another vehicle that let you adjust three feedback parameters: gain, setpoint and damping. Damping is to cruise control what shocks are to your suspension: it keeps your speed from bouncing around.

If your cruise control is overdamped, your speed drops off when you go uphill and rises when you go downhill; i.e., it doesn't follow the setpoint well.

If your cruise control is underdamped, it constantly tries to adjust speed a bit too dramatically, and constantly overshoots and undershoots the setpoint. This is exactly what is happening to you. When I played with the damping adjustment on that old aftermarket cruise control it did exactly what you describe, and leaving it overdamped like that made me car sick.

If your cruise control is "critically damped" it approaches the setpoint briskly but does not overshoot, and it maintains the speed at the setpoint without surging and backing off. In other words, it works the way it's supposed to. My TDI Jetta's cruise control is wonderfully "critically damped".

All this is useless in a practical sense, though, because the TDI cruise control is one of the functions of the ECU, and it is achieved in software. You can't physically adjust it, it has to be programmed. I don't know if there is an adjustable damping parameter, but that's probably what's wrong.

Suggest you contact your Upsolute dealer to see if there is any possibile connection with their mod. If not, demand that the VW dealer make it right because by the way you describe it, something is wrong in the ECU. I've seen many posts about how stable the cruise control is on our TDIs.

------------------
2000 Jetta GLS TDI Silver/Gray
1989 Dodge W250 Cummins Turbodiesel

 

[Max Torque]

Thank you all for the replies.

george cumber: good idea, but the fluctuations are too rhythmic to be a switch problem.

The Ripster and Marissa: Thanks for affirming the problem. Sorry to hear that you have it too and the dealer was unable to fix it.

Al Kane: Good info. Yes, it seem like the problem is lack of damping. It overshoots when making corrections. I also had an aftermarket cruise control. I installed a Sears model on my then brand new 86 Golf diesel. It still works on that car to-day.

An important question is, does re-programming “the computer” affect the Upsoluted portion of my ECU? Does anyone know? Valois, can you help?

 

[fnj2]

99.5 Golf automatic - cruise control surging - same thing you describe. At times it has been pretty bad at 55. For a while the $%$%& thing would downshift into 4th on a very gentle upgrade at 55, it was surging so strongly.

You know what? Over time it has gotten much better. I think the "memory" was filled with bad data when I got it, and I "flushed it out", just driving a long way at that speed, very steady, with the cruise control on. It seldom is very noticeable any more, and never has that downshifting problem returned.

I know it sounds crazy. I just live with it. It really isn't bad any more. 5-speed owners have no idea what we're talking about; it never happens in a 5-speed.

 

[Hannu]

Exactly the same problem here! Glad to hear I'm not grazy :=). VW says that everything is OK

------------------
-99 102 hp tdi caravelle, auto

 

[Marissa]

I can probably tell you what it isn't! My 2000 Golf has been in the shop 8 times and 24 days for the same transmision slip problem since I bought it. I had noticed the cruise control lurching at that time but it was minor by comparison.

They started off by replacing the MAF twice, the EGR, pulled the entire intake and cleaned it and the ports, replaced the throttle position control, then finally settled on pulling the entire transmission and replacing the guts (except for torque converter). It took all this before they ended solving the slipping. This was just last month.(Feb 2001). I was boardline "LEMON LAW" material.

Since buying the car I have: Absoluted, PVC/EGR mod'ed, piperized intake, ram air'ed intake, cut hole behind the intercooler, insulated the entire intake to the turbo charger.

and the CRUISE CONTROL PROBLEM STILL OCCURS INFREQUENTLY.

[This message has been edited by Marissa (edited March 16, 2001).]

 

[valois]

Max torque, sorry I did not see this thread until now, I have been busy, anyone that has a question such as this can send me an email directly, thats what I am here for. What your dealer is recommending is recoding the convienience functions, this will not affect upsolute programming at all, they will not be able to detect the chip either unless they drive the car hard. So, no, it will not change the upsolute upgrade. Unfortunately I doubt it will solve this problem either, I believe this problem might be related to the engine speed sensor. Good luck.

 

[Max Torque]

Thanks for your reply Valois. I am taking the car to the dealer next week for the second oil change and will get them to re-program. It culdn’t make it any worse. But, like you all say, it probaly won’t help either. Ahh - well...

Max

 

[Frank TDI]

The cruise control om my 1997 Jetta TDI is VERY smooth with its control. My 1999 Golf TDI is NOT. The 97 holds speed to the mark! The Golf varies about 1-2 mph.

------------------
Frank TDI
1997 Jetta TDI- UPSOLUTE TB + TT Stainless
1999 Golf TDI- TB + TT Stainless

 

[Max Torque]

To-day I had the dealer perform the procedure to “Reset the cruise control to basic settings with computer”. They did a road test after and found that they hadn’t fixed the hunting. What can I do next? It seems like lots of cars are affected.

Max

 

[The Ripster]

Shoot it!!! No seriously I doubt that they will ever fix it. I have almost eliminated mine with the .184 injectors. Now do not go out and put them in thinking it is a cure all, because it is still there, but at a very tolerable level, until they finally figure it out and I agree with Valois, it has to be related to the speed sensor and how it uses that sensors inputs.

 

[Dillard Diesel]

My 99.5 Golf GLS 5-Speed has cruise control surging as well. It does not seem to be as intense as what you guys are reporting but still noticeable nonetheless. I notice it most around 40-50 mph and cannot detect the lurching @ higher speeds on cruise control. Hope this helps.

 

[zanzabar]

Resurrecting this thread.

I've noticed this CC fluctuation since my car was Upsoluted. If that 50rpm resolution for the cruise controller is true, perhaps the added torque from the Upsolute program is making the fluctuation more noticeable. And, I only notice it at slower speeds (less than 60-65mph) where torque is probably at its highest.

Has anyone found a fix for this? Or does it truly "fix" itself. Does it only occur on 1999.5-2000 model year TDIs?

 

[George870]

I posted about this topic over a year ago (I think) in one of the other forums, but I couldn't solve the problem then, either. I have a 2000 A4 automatic, and the surging from the cruise has been evident from day 1, and it is still ANNOYING! I have a friend who normally drives like this, though (on & off the gas for no apparent reason), and I told him once that he needed to be critically damped. He didn't get it.

I think I posted in the "general discussion - A4" forum. In couldn't find my original post, but I found another that seems related:
Linky 1

I took my car to the stealership several times while the car was still under warranty, and each time, a different service guy would tell me that they couldn't find a problem. Finally, I went on a test drive with a service tech, and proved to him that there was a surging in the cruise control. Know what his response was? "All cruise controls will do that." Um, OK. I guess it's useless to argue.

I totally agree with the Al Kane's previous post. Being an engineer myself, I think this is probably in the programming of the ECU. I just don't know if it's adjustable (VAG-COM?).

So far, the problem has not "fixed itself" after 67k, other than the fact that I just don't use the cruise anymore.

 

[weedeater]

Interesting. My Volvo Turbo with an automatic used to do the same thing. An independent mechanic told me that it was a common problem with previous turbo'ed engines and the fix had been for the computer to disable the turbo while in cruise. Increased boost caused engine power to come up too quickly and the engine would always overshoot speed.

Sounds like what these cars are doing, but only in the automatics. My manual is rock-solid on speed control (unless the turbo goes out). To my knowledge, these cruise parameters are not adjustable. I bet what is happening is that the auto is disengaging the torque convertor causing the engine to speed up. Ergo, a mismatch between the cruise control programming and the automatic tranny computer.

Unless VW makes a fix, I think you're stuck with it.

 

[mcwig]

Mine doesn't fluctuate much once engaged, but it does have an annoying 3-4mph overshoot when first engaged at a slower speed than the set speed. This is especially annoying when you want to bump up the set speed a little with the cruise engaged by tapping on the accel button.
The cruise is definitely underdamped, and this really is too bad, because it pretty much has to all be controlled by software. I have not been able to find any way to adjust the control loop with VAG-COM.
The problem is a little worse when the engine is in the vicinity of 2000rpm. This makes sense, as the throttle is more responsive there due to turbo boost. More gain in the control loop means less damping (all other things being equal).

 

[tadc]

Anybody tried to address this problem by making Injection Quantity adjustments?

 

[zanzabar]

Anybody tried to address this problem by making Injection Quantity adjustments?

Well, I've had a few different IQ settings in the last month or two (between 6 & 8), but right now it's practically maxed out "lean" at 8.0. Honestly I didn't pay attention the the CC at those different settings (just trying to lower the smoke), but I'm thinking that a lower IQ value will only make the problem worse. This problem is still happening on my car, but I'm not extremely worried about it.

 

[BAMA TDI]

This may be a stupid observation, but I had Japanese make of car with an automatic do the same thing. Especially goint up/down hills on iterstate. Get it above the rpm where the torque band peaked and it was not as bad but it would still do it. Had another Japanese make of car with 5-speed. Below torque band peak it would hunt up and down as well. Above torque band peak it would do fine. Yeah, I have a 2000 Jetta GLS TDI with 5-speed and I can say I have never had this problem with it.

 

[ukguy]

Hi there,

I know this thread is pretty old, but I have the same issue with my Golf 1.6TDI CR Bluemotion 2011 model with 97K miles. Did anyone get to the bottom of it and whether there was any adjustment that could be made by VCDS to dampen it somewhat?

Between 40-50mph, my cruise control fluctuates, not to the point where the speed changes by more than 1mph either way...it's just like the throttle is blipped then leaned then blipped again and again... Annoying considering the car drives so well with the cruise control off. Thanks.