'04 PD Jetta Cruise Control Issue

Brokk

Veteran Member
Joined
Sep 30, 2005
Location
Selah, WA
TDI
'04 GLS TDI JETTA
Lately while driving on the freeway, with cruise set usually somewhere between 60 and 75, occasionally my car will slow down. I can just cancel the cruse speed back up and reset the cruise and all is fine for a while again. If I don't do anything about it after a little while the car will rapidly accelerate back up to the correct speed. This is happening on flat stretches of road.

What might be causing this?

Thanks,
 

2004STARWARSTDI

Top Post Dawg
Joined
Oct 19, 2004
Location
LAKELAND, FL
TDI
2004 Platinum Gray GLS Jetta / 2006 Silver Jetta with DSG
Cruise

Did you ever have your Brake light switch replaced under the free recall? A failing brake light switch will affect your cruise.
 

dieseltdi

Member
Joined
Sep 30, 2001
Location
Grapevine, Texas, U.S.
TDI
soon to be 82 Vanagon TDI
cruise problems

I had the same problems and I at first thought it had something to do with the glow plug reflash. However, other problems began to surface after a few months: poor idle, hard starting, missing and poor acceleration. On a whim, I tested the lift pump and found that it wash't working. Once I replaced the lift pump, all my problems disappeared, INCLUDING the cruise problems. Hayden
 

Brokk

Veteran Member
Joined
Sep 30, 2005
Location
Selah, WA
TDI
'04 GLS TDI JETTA
Thanks for the suggestions. I did have my Brake light switch replaced under the recall and that fixed an issue where the cruise would turn off. This is different because the cruise stays on but just allows the speed and RPMs to die down for a little bit and then it comes back very quickly after a little while if I let it. Because it usually happens on the freeway I don't let it because it accelerates too quickly for me and I don't like letting the car drop down from 65 to like 55 on the freeway.

I will watch for the other problems you talk about dieseltdi.

How do I go about testing the lift pump?

Thanks,
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
I would suspect the EGR control ciruit. It can take the air flow so low that fuel is not allowed to go very high - reducing the available power.

Even a very tiny air leak in the charge air system can greatly exacerbate this. Is your final rubber hose to the intake manifold (ASV-EGR assembly) sealing tightly? Or is it tilting out on one side?
 

Brokk

Veteran Member
Joined
Sep 30, 2005
Location
Selah, WA
TDI
'04 GLS TDI JETTA
Dan,

That is the hose that many people use a "Dog Leash" or "Doggie Collar" to keep it from coming loose right? I will go check it this afternoon. I replaced it once a few years ago and wish I would have just bought the "Dog Collar" back then.

Thanks,
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
That is right. Whitedog's doggie Collar, now sold by Kerma, I think.

I often screw in a self tapping sheet metal screw with a hex head, say a #10. Then take a 4" wheel and a dremel and shape the head to replace the missing ramp and face that the wire bail should clamp behind. I try to twin the usually undamaged other side. This also works very well, is cheaper, and has no shipping time delay.

Though on my personal car I do have one of Whitedog's originals - from before his deal with KERMA.
 

dieseltdi

Member
Joined
Sep 30, 2001
Location
Grapevine, Texas, U.S.
TDI
soon to be 82 Vanagon TDI
The way to see if you lift pump is working is really simple. Remove or tilt the bottom of the rear seat. Remove the cover on that reveals the lift pump/fuel sender. Put you hand on the top, and then turn the key to the glow position, you should be able to feel and or hear the pump initiate. Mine was completely dead, no noise no vibration, You may actually have to turn it almost to start but you don't actually have to start the car.
 

Richptl

Vendor
Joined
Jan 11, 2011
Location
Apalachin, NY
TDI
2004 Jetta TDI automatic 305,000 miles
My 04 has a weird issue also. The cruise only works while the right turn signal is on. This started a long time ago and it used to be where I could turn the signal on, set the cruise, then turn the blinker off. Now the cruise won't work without the right turn signal. I've cleaned all the grounds on the car and checked for bad bulbs. I just live with having no cruise control.
 

matgat

Veteran Member
Joined
Jul 21, 2011
Location
Sorel, Canada
TDI
2004 Jetta TDI
The cruise control on my 04 Jetta works perfectly in the winter but when we hit hot temperature, I have the same problem as you OP.
 

anderspy

New member
Joined
Jun 23, 2013
Location
Vermont
TDI
2004 Jetta Wagon MK4 (PD)
solution?

Lately while driving on the freeway, with cruise set usually somewhere between 60 and 75, occasionally my car will slow down. I can just cancel the cruse speed back up and reset the cruise and all is fine for a while again. If I don't do anything about it after a little while the car will rapidly accelerate back up to the correct speed. This is happening on flat stretches of road.

What might be causing this?

Thanks,

I have the exact same symptoms, and the problem appears to be the MAF sensor. I believe this because when I unplug the sensor the symptoms go away and the cruise control works fine. You could try the same experiment. I ordered a new MAF sensor from http://www.ecstuning.com for only $60, and will report back when I install it and confirm the diagnosis.

Afaik, if the MAF sensor is unplugged then the ECU just assumes that the air flow is as specified by the computer so the fuel flow is not adjusted to the airflow, which may hurt performance and/or fuel efficiency. But it must be the bad values from the failing sensor that makes the cruise control flaky.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
It could be the MAF, or a boost leak, or an EGR issue. With the MAF unplugged a substitute air flow is used, lower than normal full air flow, so slightly less power (unless you have a tune) and the EGR does not try to operate.

So unplugging the MAF can mask several issues.
 

firehawk682

Member
Joined
May 1, 2013
Location
Iowa
TDI
2005 MKIV TDI
Any fixes for this problem I'm having the same issue only when it's hot out. I changed my lift pump bc it wasn't working with no change to the problem.
 

Richptl

Vendor
Joined
Jan 11, 2011
Location
Apalachin, NY
TDI
2004 Jetta TDI automatic 305,000 miles
Mine will work with the right blinker on. Anyone else noticed behavior related to the turn signal? I sprayed electrical contact cleaner into the turn signal stalk. I suspect a bulb issue somewhere on my car.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
Rich, So you know that you need to examine your wiring inside the stalk and column and perhaps the brake switch functionality? You need to use VCDS to check out the switches and find out which wire is bad.

Hawk,
You are almost certainly having problems with air flow management. EGR and or MAF. Look for and fix any leaking seals on your charge air system. Ensure your measured air flow is normal (VCDS use again).
 

Richptl

Vendor
Joined
Jan 11, 2011
Location
Apalachin, NY
TDI
2004 Jetta TDI automatic 305,000 miles
My cruise is low priority. The last few weeks I've put a lot of time into fixing the front suspension issues. I don't get the brake light fault code. The cruise acted flaky when I bought the car and contact cleaner fixed it for a while.
 

Richptl

Vendor
Joined
Jan 11, 2011
Location
Apalachin, NY
TDI
2004 Jetta TDI automatic 305,000 miles
FYI I did change my turn stalk switch a while ago and that fixed it. Cruise has been working fine ever since.
 
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