I'm thinking AIC myself... - Saab 9000 Bulletin Board - Saabnet.com
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I'm thinking AIC myself...
Posted by David Ingram (more from David Ingram) on Wed, 3 Sep 2008 13:59:07
In Reply to: '87 deceleration dashpot, fplatt, Tue, 2 Sep 2008 10:52:06
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The only purpose of the dashpot was to slow the car's return to fully closed throttle to improve emissions (lots of incomplete combustion otherwise, apparently). So a non-functioning dashpot shouldn't really affect your idle.
Well, now that I'm writing that I'm forced to question my own logic. What I was going to say was that it shouldn't matter and the AIC (automatic idle control valve) may be sticking or otherwise malfunctioning. However, on second thought it would seem likely that the engine computer expects the dashpot to be working and will thus instruct the AIC to restrict the airflow on the assumption the dashpot's holding the throttle open a bit.
That suggests a failed dashpot could indeed be throwing off the works, creating lower than expected airflow overall to the intake, and thus the bottoming out of idle right at the release of throttle.
Since you've replaced the AIC from the sound of it, then it makes sense to look at the dashpot.
Should be cheap and easy to locate a new/used dashpot I would think.
Past that, I agree with vacuum leaks, and check your plugs for proper gap. Also check to see if the bellows to and from the intercooler are loose/detached/obstructed, and likewise check the rest of the intake plumbing for looseness and/or obstructions. Don't overlook the hose to the charcoal canister in the passenger fender, which likes to fall off, though that would usually be a big enough leak to set of the check engine light.
posted by 68.195.246...
Posts in this Thread:
- '87 deceleration dashpot, fplatt, Tue, 2 Sep 2008 10:52:06
- Are you on the East Coast / Delaware., Saabnutt, Wed, 3 Sep 2008 18:32:18
- Re: '87 deceleration dash-pot / AIC Valve, Saabnutt, Wed, 3 Sep 2008 18:28:08
- I'm thinking AIC myself..., David Ingram, Wed, 3 Sep 2008 13:59:07 <-- Viewing This Message
- Re: '87 deceleration dashpot, Craig, Wed, 3 Sep 2008 06:31:02
- Dashpot is purely mechanical, Ari
, Tue, 2 Sep 2008 12:19:55
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