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A couple of things to mull over... (long)
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Posted by Micah in NC [Email] (more from Micah in NC) on Fri, 23 May 2003 10:55:40 Share Post by Email
In Reply to: Cool start problem, EDZ, Fri, 23 May 2003 09:21:26
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EDZ,
I have an '84 S and it did the exact same scenario. (In fact, I've had two '84Ss, and both went threw the same fits which your Turbo does.) I stumbled upon the fix while reading up on CIS info at the Townsend website. (It is linked at bottom of page.) The same thing could be causing your Turbo's cool-starting/idling problems.

Here is someone's thread from her '84 900 saga with same problem:
URL: http://www.saabnet.com/tsn/bb/900/index.html?bID=169200

In between the lines below is my response to her post.

--------------------MY ORIGINAL POST---------------------------
This COULD be your problem:
This scenario only applies if your car goes through the "idle dipping down to almost nothing" during most warm-up periods when the outside air temperature is below 70-75 degrees F. (Sometimes it is barely noticeable.)

If so, your idle problem is like mine was, and it baffled me for years (not to mention the annoyance factor). The culprit was the black tipped thermo-switch which resides just under the thermostat housing, just below the large topmost radiator-to-engine hose. It reads the coolant temperature and (if still the black-tipped factory part) senses when the coolant reaches about 70-77 degrees Fahrenheit.

Then, when this temperature is achieved, it allows the CIS control (computer) unit to "listen" to the signal from the oxygen sensor, which is screwed into the exhaust manifold. The O2 sensor reads--you guessed it--the oxygen content of the exhaust which varies according to a too rich or too lean fuel/air mixture.

SAAB put out a Technical Service Bulletin (TSB) on these cars (84-85 base & 'S' models & 84 turbos) which told dealers to replace that black-tipped thermo-switch with one that is red-tipped and lets the computer start "listening" to the O2 sensor at 100-110 degrees F.

I was able to obtain a black-tipped switch by searching on the Web for part the part. It is a simple fix, but the switch is hard to find.

I have included a link to hopefully explain this mess. It links to Tom Townsend's informative website. It is a page which contains scans of the original SAAB technical service bulletin sent to mechanics on this very problem.

An associate of Tom's, Ywan Mason, told me that you don't even have to do all the rewiring the TSB suggests. He said to merely replace the black-tipped switch with the red one. And it works!

The black-tipped switch was standard on the 1986 8V engines, as SAAB had realized the fix was needed by then.
-------------------------------------------------------

Here is the URL of an ANOTHER old post of mine on this topic, too. (Read it if you have time. In it, KevinK and others helped me understand what happens as a 8V CIS 900 warms up.)

The URL (copy & paste): http://www.saabnet.com/tsn/bb/900/index.html?bID=212742

Hope this helps!
Micah in NC
'84 900S, 236K mi.
'89 900S, 108K mi. (project car)


posted by 216.77.23...

Click here for SAAB technical service bulletin on '81-'85 CIS 900 cold start problems, on Townsend Imports' site.

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