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Date: Wed, 11 Nov 1998 14:16:11 -0800
From: Justin VanAbrahams <jvanabranopsamnet>
Subject: Re: Idle/APC tuneup on 84 900T


James F. Causey wrote: > > I have an 84 900 Turbo recently purchased with 160K miles... thanks to > everyone who gave fluid info in response to my recent questions. Congrats! The '84 900s were (IMHO) the best year of the 8v turbos and pretty rockin' cars... my '84 was great and is sorely missed... > Now, I believe it's time the old Saab had a tune-up. The idle is rather > rough at all times, and a bit low -- when the car is started (especially > when it's cold), I have to *gently* (so as not to rev the engine too > much) give the car throttle to keep the idle up so it doesn't die. And > if I get going while the engine is still cold, it'll die at the first > stop light/stop sign and need to be restarted. The idle problem could be a misadjustment of basic idle - resetting it is kinda complex, but can be found at Towsend Imports' site. But, before screwing around with that, I would post-haste acquire a new set of ignition wires and spark plugs - a $100 (max) investment that definitely needs to be done on a 160k car... buy only Bougicord or Magnecor wires - don't buy Bosch wires as they aren't particularly good. NGK or Bosch Platinum plugs are a good bet - I prefer NGK over Bosch. You will likely have to special order the plugs as most auto parts places don't stock them. Also, check every last little bit of vacuum hose - make sure all connections are very solid. If they're not, replace the hose or use a small zip tie to secure to hose to the nozzle/nipple - this alone could cure the stalling and rough idle. Failing all of this, your idle control valve could be out of wack - they do die and cause wavering idle conditions. Townsend Imports is a good source for any and all Saab parts. > I've also noticed that the turbo/APC gauge stays in the first, large > white band most of the time -- when under load (accelerating), it'll live > in the neutral band, or crank up into the boost when accelerating more > rapidly or going up a hill in fourth/fifth gear or something, but > otherwise it's in the first white. I didn't think anything of it, until > I read on a web page recently someone mentioning that this meant the APC > unit needed adjustment. The Turbo/APC gauge measures both boost and vacuum. The white area on the gauge is vacuum - i.e. the engine is sucking air. The yellow area is normal boost - when the turbo is pumping away the needle should stay in the yellow zone at [almost] all times... the turbo does not provide boost under "cruising" conditions, so you'll only see the needle go here during load (e.g. uphill) or acceleration. The red zone should not be used most of the time - on occassion, under heavy load for example, the needle will sometimes pop into the red zone, but it should not go here often or without provocation. If it does, something is damaged or misadjusted. > Thus, I'm curious what tune-up steps I should try from here. I know the > car can use a new distributor cap and rotor, and I'm going to change the > plugs and wires, air filter and fuel filter too... any other > suggestions? If I'm going to try to adjust the APC unit myself, do I > need any special equipment? I strongly recommend dropping $50 and buying a Bentley 8v manual for your car... it'll have all the info you need and more... and it's well worth the money. In fact, I've come to prefer the Bentley manual to the "real" Saab service manuals in almost all respects. Amazon.com stocks the book, as will most online auto books stores and probably even your local Saab dealer... Good luck! -Justin

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