Thermo-time-switch/ cold start valve- poor running

[Ti Kan]

Aaron Ryba writes:
> What function does the thermo-time-switch have?

Controls whether the cold start valve should be activated during
cranking, and the duration of its activation.

> Does it control the cold start valve? The valve only?

Yes.

> Where exactly is it located? (toward rear of head?)

On an I5, on the back of the head.  On an I4, on the top
radiator hose flange.

> Of what temp does it monitor? (Coolant?, head itself?)

The bi-metallic element inside the switch, which is heated by:
1. The internal electrical heating element
2. temperature of the coolant and the head

> What is the cold start valve? Is it just an extra
> injector, electronically trigered?

Yes.

> Where does it spray extra fuel and when?

During cranking (ignition key in the "start" position)
and only when its cold enough (controlled by thermo-time switch).

> Into the mechanical fuel dist.?

No.  Into the intake manifold.

> For a while I have experienced a sporatic poor running
> condition of my 87 4kcsq. Symptoms include very rough
> idle, extreme loss of power, sulfer-esk smelling
> (exhaust?) odor, misfiring-like noise and noise from
> air pressure plate slamming. This only happens for
> about 10 seconds at a time and happens sporatically
> sometimes during warm-up, most often during highway
> cruising. Often happens when engine temp is low but
> not always happens.
> The car never has a hard time starting though, cold or
> warm.
>
> I am thinking a faulty thermo-time switch, cold start
> valve or a ground in the wiring between the two might
> be the problem.

No.  Once the engine starts to run (your ignition key
is returned to the "run" position), the thermo-time switch
and the cold start valve are no longer active at all.  These
are cold *starting* aid devices, not cold *running* aid.

Check the temperature sender that feeds the CIS-E control unit.
You should also check for air leaks, and diagnose the problem
using the procedures outlined in the Bentley, such as checking
the oxygen sensor, basic fuel pressures, fuel air mixture,
differential pressure regulator current, etc.

-Ti
2003 A4 1.8T multitronic
2001 S4 biturbo 6-sp
1984 5000S turbo
1980 4000 2.0 5-sp
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