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Re: [T3] Idle question

On 17 Jan 2003 at 14:21, Roush, Norman wrote:

> 1968 Squareback w/FI all stock
> Start fine
> Idles @ 1100-1200 when cold
> Runs fine
> Idles @ about 800 when warm for a while
> Then drops to 600 jumps to 1000 and drops to 800 again 
> But still runs fine and smoothly
> At night I do notice the headlights dim and brighten with the idle fluctuation
> Points/plugs/trigger points/timing/value adjustment all OK
> Check fuel pressure some time ago but was at 28-30 lbs
> Any ideas?? Throttle switch, recheck fuel pressure?

I'd check the throttle valve switch. With the engine off, and working in the 
engine compartment, you should hear the 68 TVS click after you just open the 
throttle a tiny bit. You should hear it click as you open the throttle and 
again as it closes. You want the click to occur as close to the fully closed 
position as possible WITHOUT failing to close at any time when you let up on 
the throttle. The best test of this would actually be to have someone up front 
move the throttle via the pedal while you listen from the engine end.

Your symptoms really don't ring much of a bell with me, but it is possible that 
your TVS switch point is adjusted so close to the closed position that it is 
spontaneously tripping back and forth just from engine virbration. One way to 
check for this would be to wait until your engine is doing this and then, 
without touching anything else, unplug the TVS. If this behavior changes, this 
may be your problem.

Of course it might also be bad connections/intermittent wires in any number of 

Note for the rest of you. Only the 68-9 TVS (with 2 terminals) makes an audible 
click. The other years have to be tested electronically.

Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

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