cruise control antics

Brett Dikeman brett at
Tue Jan 11 18:06:26 EST 2005

> On Tue, 11 Jan 2005 11:54:07 -0500, Nick Lawrence <nick at> wrote:
>> I was going to ask a similar question....
>> My '90 200TQA with increased boost, (1.7 bar), changes speed too fast,
>> then
>> coasts, (high vacuum) when using cruise in slightly even terrain.
>> doesn't do
>> this when boost is near stock. Anyone else experience this?

Putting a restrictor in the line to the vacuum actuator might do the
trick, but would probably make it slow to release as well, which does not
sound very safe.  Sounds like you've got something else going wrong, like
a wastegate that has been fussed which case cruise control
problems like yours are a symptom of a different problem, probably.  Who
knows, might be the linkage binding up- shoot it with some lube like
Boeshield or white lithium grease and oil the return springs as well.

The 200q20v has an IA stage III+ chip and will respond faster than a k26
10v, but I've never really had problems with cruise control overshooting. 
When it was working properly, it would be...enthusiastic...about getting
up to speed.  However, once it hit the target speed, it was equally  
abrupt about cutting back power.  Ever seen Spaceballs, ie "ludicrous
speed"?  Sorta like that.

It's amazing how "context-sensitive" horsepower is.  Set CC to 65-ish,
forgot about it, and two hours of highway cruising later at 70, cruise
control out of sight and out of mind, coast for your exit.  Coming up on a
tractor trailer taking the same exit as you, suddenly you're not coasting
anymore.  275-ish HP feels like 400 right about then.


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