[T3] '72 FI won't idle down

[Jim Adney]

On 11 Jun 2026 at 22:02, Keith Park wrote:

> Tends to open too quickly when the engine has been shut off and then the idle
> is too high till it closes AND the engine runs too lean till it closes 

If you believe this, do you also believe that opening the throttle leans the 
mixture? (It's the same thing.)

The answer to both is, no.

Other systems take input from a throttle position sensor, but our TVS is just 
a switch, which doesn't sense position. It has contacts to inject single pulses 
of fuel, but no general input on leanness/richness.

Yes, various things add intake air. The pressure sensor and the brain sense 
that and respond wth more gas. Yes, it's a primitive system, and the 
accomodation is imperfect, but adding air leading to leanness, is just carb 
thinking.


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