RE: 2.0 16v [Idle Hunt]

[16V Jason <jason@scirocco.org>]

At 02:59 PM 10/30/2001, Michael Abatzis wrote:
>hmmm. mine's been doing that too following the 2.0 swap. initially high 
>idle after the swap. now it fluctuates around 100-200 of 900 rpm. when the 
>clutch is pushed in after the engine's revving high, the rpms will drop 
>abruptly, then have a wider amplitude cycle before leveling out. if the 
>car is cold it'll stall. haven't had a chance to look at it yet. sound 
>familiar? lmk if you figure it out...

Mine did it too right after my 2.0 swap.  The reason turned out to be 
ignition timing that was off.  Check your timing before you do anything else.

Then check and clean the Idle Stabilizer Valve (ISV).  Take it out of the 
car, turn it on its side and spray lots of brake or carb cleaner in 
there.  Spray it 'till it comes out clean. This solves a lot of idle 
surging problems as well as stalling/almost stalling when the revs drop 
quickly.

The other thing that I would recommend checking is the throttle rest 
stop.  Remember that a 2.0 is sucking 11% more air at all times than a 1.8 
would... including at idle.  With your car warm and idling, yank the plug 
off of the ISV.  Without having the Bentley in front of me, logic tells me 
that your idle should stay around the same, if anything fall slightly.

Remember that the ISV works by adding additional air bypassing the throttle 
and going to the cylinders.  More air (and therefore more fuel) = higher 
RPM.  If your throttle stop is set so low that the engine won't run at all 
without the ISV, check and adjust everything according to the Bentley.  The 
less the ISV has to do, the better idle quality you'll get.

FWIW my 2.0 doesn't really fluctuate at all at idle.  It stays right around 
900.

Jason


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