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Cruise Control

R

Rodney Kelp

The cruise control on my 2001 Jetta TDI no longer maintains speed going up
hill. I have to feather the gas pedal to maintain speed. It worked fine up
until about 70k miles. There are no error message on the dash board or on my
OBDII diagnostic meter. What circuit could have failed?
 
K

Kim

Just a guess, but the throttle linkage from the cruise controller may have
either stretched, or slipped, I don't think that its a electronic failure.
Kim
 
P

Phil Durgin

This may also be a vacuum leak.
Turn on your air conditioning.
Does it die while you are going uphill as well?

If it does, you have a vacuum leak and need to replace the hoses and the
check valves on the car.

Phil Durgin
Kirke Computers
 
B

BWL

I had this problem on a service truck I used to drive; turned out to be a stuck
check valve in the vacuum system.
 
D

DaveC

So, the CC works fine all the time, except when you get to a steep hill?

Is this an automatic trans? Is it downshifting like it should? If not, could
be a transmission problem.

But it does sound like the gas pedal isn't being pulled all the way to the
floor (if you can "pump" the pedal, it isn't at the floor). Which points to
problems with either a linkage (cable IS the linkage, in this case) that
needs lube (grease and/or oil all points from the pedal to the throttle body)
or a vacuum leak.

You can test the vacuum "pot" that actuates the CC by pulling off the hose
and attaching a vacuum pump (MityVac is a popular brand available on-line and
at some auto parts stores) to it. Pump it up (or down, in this case :) and
see if it will hold vacuum.

The vacuum system consists of more than just the CC pot, however. Could be
leaky hose or a canister that won't hold vacuum due to a split, crack, hole,
etc.

Diagnosing needs to be done.

Good luck,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC
[email protected]
This is an invalid return address
Please reply in the news group
 
J

James Sweet

DaveC said:
So, the CC works fine all the time, except when you get to a steep hill?

Is this an automatic trans? Is it downshifting like it should? If not, could
be a transmission problem.

But it does sound like the gas pedal isn't being pulled all the way to the
floor (if you can "pump" the pedal, it isn't at the floor). Which points to
problems with either a linkage (cable IS the linkage, in this case) that
needs lube (grease and/or oil all points from the pedal to the throttle body)
or a vacuum leak.

You can test the vacuum "pot" that actuates the CC by pulling off the hose
and attaching a vacuum pump (MityVac is a popular brand available on-line and
at some auto parts stores) to it. Pump it up (or down, in this case :) and
see if it will hold vacuum.

The vacuum system consists of more than just the CC pot, however. Could be
leaky hose or a canister that won't hold vacuum due to a split, crack, hole,
etc.

Diagnosing needs to be done.

Good luck,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC
[email protected]
This is an invalid return address
Please reply in the news group

What sort of car is this? There's newsgroups for a great many types of car,
usually alt.autos.brand. Try posting in there, you may have a common problem
that other owners will be familiar with.
 
P

papapeng

The cruise control on my 2001 Jetta TDI no longer maintains speed going up
hill. I have to feather the gas pedal to maintain speed. It worked fine up
until about 70k miles. There are no error message on the dash board or on my
OBDII diagnostic meter. What circuit could have failed?


Happened to read a multi page article on cruise control problems and
theory in the current issue (Aug 04?) of Popular Mechanics (Popular
Science?) at the library. I thought it very helpful to understand how
the many types of cruise control systems in the market work.
 
G

gothika

Happened to read a multi page article on cruise control problems and
theory in the current issue (Aug 04?) of Popular Mechanics (Popular
Science?) at the library. I thought it very helpful to understand how
the many types of cruise control systems in the market work.

The cruise control in my Toyota minivan is electronic feedback via the
computer to a control servo conected directly to my gas pedal cable
linkage. Very foolproof design that always works, it just increases
throttle to the cable control that runs from the gas pedal to the
injector throttle body.
 
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