Warm running CIS problem - Update

[Cory_Langford at bcit.ca (Cory Langford)]

Was mulling over the problem last night and had an interesting thought.

It seems that the car tends to start having issues when the term. time 
switch cuts out, and seems to run better when the switch cuts in.

I thought this very odd as I have unplugged the cold start injector as a 
simple test to see if it was causing issues. 

So this morning I watched it closely, and it seems to be dead on.  It 
looks like at the point the term switch kicks in the car runs well. It 
does so for about 3 minutes after the point where the switch should kick 
out. 

So how long does the term switch stay active after it reaches temp?  About 
3 minutes?

One other thing I noticed this morning (paying a bit closer attention 
now), was that when the water temp was at the point where the term. time 
switch should be cutting out the voltage drops from just over 13V to about 
12.5V.  As time goes by (or temp rises) the car runs worse.  When it 
starts to have the idle rolling issue the interior volt meter is running 
at about 12V-11.5V.  When the rad fan kicks in I notices the voltage drops 
to 11V.

My latest theory - the term. time switch is actually shorting the +12v 
connection it has to the block when it heats up.

I am thinking this would result in a slow loss of voltage to the coil, and 
hence the slowly degrading performance.  It would also explain the a/f 
meter starting to read strange as the block is the ground for the o2 
sensor, and if we feed a constant voltage to it the o2 transferring that 
voltage back through the sensor to the gauge and thus I get the -ve 
0.4-1.1V readings on the sensor wire (instead of the +.5v range).

Anyone have a bad term. switch short?

I guess that is my next step.  Grab another one from the bone yard to see 
if it changes anything.

Sound plausible?


Cory Langford
'86 Roc turbo, 
'78 Roc turbo - Daily driver project,
'65 Ghia Coupe
95 Eurovan, etc, etc... :)