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Re: Fluctuating Idle
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Posted by Michael [Email] (#1365) [Profile/Gallery] (more from Michael) on Fri, 18 May 2001 02:52:33 Share Post by Email
In Reply to: Fluctuating Idle, Marcus, Thu, 17 May 2001 20:46:43
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Well, this problem I'm quite familiar with. I'm the owner of a well cared for 82 Turbo, after previously owning a non-Turbo 82 900. The advise given so far is all very good. A new O2 sensor could do the trick. Also finding any obvious and not so obvious vacuum leaks. Two areas that I discovered to be problematic are the injector valve rubber seals (they harden and shrink with age, thus allowing air to seep into the intake manifold), and the auxilary air valve. Even if the aux/valve works as per the recommended test, check the valve structure integrity. What you do is remove it, close off the top orifice with a thumb, then blow hard with tightened lips around the bottom orifice. If you hear any air leaking - voila, a vacuum leak. What I did to remedy that was apply some JB weld compound around the entire pressed metal seal (where the upper and lower pieces of the unit were joined during manufacture). Problem solved.

Also check for air leaks on the EGR valve, as well as the vacuum advance unit on the distributor - both of which have a flexible rubber diaphragm inside that can rupture. Another possible diaphragm to check is the little black plastic boost pressure switch that's also connected to the vacuum system. I also suggest cleaning the electric contacts on all the assorted components.

How'd I discover all these problem areas? Well, I'll be honest and admit that I drove my non-T 900 (bought it used in 95 with 175k miles on it) for years with little to no maintenance, and it was only because of guilt and embarrassment (I'm actually a former military aircraft mechanic) over the decreasing performance (including a serious idle prob) that I began to take maintenance seriously. Just about every component was in need of either replacement, repair or a serious cleaning. After a good several weekends of steady work, the accumulative improved performance was startling. Then I junked it, taking as many good parts from it as I could to help restore the 900 T I currently drive.
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