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

[Ben Swann]

Aaron,

One of two "thermo" switches was used on the earlier CIS cars to switch
vaccum on the warmup regulator - more of a mechanical action than
electrical - often a source of confusion, for me anyuway.  In addition to
the thermo-time switch that controls cold-start injector, there is the
temperature sensor or fuel injection sending unit located on the bottom of
the cooling neck of CIS-E for 5 cyl.  It is(AFAIK) a negative coefficient
thermal resistance sending unit used by the ECU for mixture control.  This
effectively replaces the vacuum switch on the Pre-84 CIS 4000Q's.  I have
been looking for specs on how to test this - Bently shows a 15 ohm resistor
used in place to check differential pressure current.

I think I have a bunch of these that are marginal and have been confounding
diagnosis on the '84 4kq I have been working on.

I found that Rod at thepartsconection.com has them for a very reasonable
price.  Bosch Part number -0 280 130 037/ VW 035 919 369 (M).  I would have
replaced with a new one earlier but dealer cost was over $100.

Now that testing them is almost a mute point, anyone have a resistance
range for these, or a value at ambient temp?

Ben
p.s.
Reading your later email -
[It sounds like there is a force slamming the air intake plate, some force
traveling back from the intake manifold.

Where exactly is the thermo switch that informs the ECU located? Atop the
coolant/thermostat housing? Or below it? (I-5 engine)]

I think the temp sensor I refer to above is the problem - I experienced the
same symptoms.  Wiggled the sendor and the engine ran great.  Replaced with
another flaky, but better sender and the engine ran good mostly, but I
think that one is out of spec. on startup - I had the same problem on the
car I took it out of, but that confirmed my diagnosis for now.

Two senders on order!


[Hello listers,

What function does the thermo-time-switch have?
Does it control the cold start valve? The valve only?
Where exactly is it located? (toward rear of head?)
Of what temp does it monitor? (Coolant?, head itself?)
What is the cold start valve? Is it just an extra
injector, electronically trigered? Where does it spray
extra fuel and when? Into the mechanical fuel dist.?
I have looked through Bently and not much is listed
for this ingformation.

This is for CIS-E controlled car.

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.

thanks in advance for responses

aaron ryba
87 4kcsq]