erratic idle ...

[tberk at sbcglobal.net (T Berk)]

Carlos Alves wrote:

> Hey guys,
> 
> My 16v has an erratic idle, I noticed that my upper air intake boot is 
> cracked, could this be the problem?? Where can I order a new one?? 
> Instead of going stock, does anyone have an after market intake 
> recommendations? I already have a K&N installed. 
> 
> Also, concerning my idling woes, I have noticed a vacuum leak on the 
> vacuum thermoswitch. If you dont know what Im talking about, look here 


<http://www.scirocco16v.com/tech_gallery/airsystem_scirocco16vdotcom.jpg>

Ooh, ohh, pictures!

> The whole switch on the side of the intake is gone, leaving me two 
> wires, one going to the preheat valve (I dont think it is necessary, I 
> actually removed this wire) and the other one going from the intake 
> manifold. The wire from the intake manifold is unconnected and is the 
> one that has a vacuum leak, but the weird thing is, my car has a more 
> erratic idle when I plug that wire up and there is no leak. Just 
> leaving it unconnected makes the care maintain a more or 
> less "unerratic" idle, but still erratic nontheless.  Does anyone know 
> what I am talking about?
> 
> I recently bought a Techtronics exhaust which bypasses the catalytic 
> converter, but its the aluminum model.  Is installation on this easy or 
> is welding required?
> 
> Thanks for all the help,
> 
> Carlos
> 

Carlos,

I left most all your text in to help get the diagnosing going.

It is my thinking you have more than one problem, the biggest of which 
is you can abide NO ail leaks.

I don't have a replacement boot and quick search of Virtual World's
<http://www.parts4vws.com> Online catalog doesn't show one. But fret 
not, Mr & Mrs. Potter are indeed wonderful Magi and can probably find 
you one if you drop them a line. (Congrats Potterpeople et all ie: One 
Lap). (You too Shawn.)

The other thing I'm (also) thinking is the temp sensor is 
misrepresenting what the coolant is doing.

Keep in mind the cascading nature of CIS (well, almost _any_ )systems; 
one thing will throw another off and lead to overcorrection in trying to 
get back to base level.

Fix the leaks and see what happens, it might just 'get better'.


hth,
TBerk