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Re: bad idling and poor running Posted by Saana88 [Email]  (#207)  [Profile/Gallery]
(more from Saana88) on Tue, 16 Jan 2007 21:16:43
In Reply to: bad idling and poor running, David, Tue, 16 Jan 2007 20:12:20 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Having to hold the gas pedal down to keep your car running is (on 8 valvers) a sign that the idle speed valve is starting to stick closed. Just above your warm-up regulator on the radiator-side of the engine, you will see a disc-shaped part with one idle hose going in and one going out. This part also has one two-pin electric connector on it. (for clarification, see Dana's 8 valve page at the link below, it's the fifth picture down). Take the hoses off and spray some penetrating oil down in the valve. That is regulated by a bi-metallic spring which is electrically heated by the harness, and when it sticks shut your engine will try to idle at around 400 RPM, nearly dying. Last time I checked, they're still available (site sponsors or from Saab, compare prices first) since they tend to die every 120-150k on my cars.
This would also be a great time to check your metering body and throttle valve. Remove the two large hose clamps holding on the boot between the top of the metering body/pressure regulator/air filter housing and the front of the intake/throttle body and pull the boot off. Using a suitable solvent, clean the deposits of oil off of the top of the disc in the metering venturi (be gentle with this and do not twist it side to side) paying particular attention to the circular seat and underside of the plate. When oil deposits (from the PCV system, perfectly normal) build up on this plate, it weighs it down and makes your car run lean. Once that is done, clean around the throttle plate as well. 8 valve 900 idle speed is governed by two things: the amount of air flowing into the engine (past the throttle valve) and the amount of air bypassing the throttle valve (through the idle speed valve).
As for the exhaust, with a loud noise you should be able to find where the leak is pretty easily. Typical culprits are where the head pipe meets the catalyst, where the front pipe meets the muffler, and where the tail pipe goes over the rear axle.
The rest of your driveability issues may be more difficult to chase down, though there are some really simple tests you can do to be sure you've checked the really cheap, easy-to-diagnose typical stuff. Now that your intake is nice and clean, check all your vacuum lines, fittings, and nozzles, including those on the charcoal canister (right in the neighborhood of the ignition amp you replaced) and everything going to and from the valve cover. Be sure your dipstick and oil filler cap (the same red thing) are seated correctly. Aside from the vacuum lines for the PCV orifice (and its rubber grommet in the valve cover) and those that supply the interior vents, the one I most recently missed was for the distributor vacuum advance. Take this line off the intake and suck on it (or use a vacuum pump) and see if it holds vacuum.
If these things don't work, it's time to troubleshoot the cold start system (with its various thermoswitches) and to ask yourself, "Self, when was the last time I changed the fuel filter and tuned up the ignition system?" Arcing ignition wires, old, old plugs and corroded cap and rotor contacts can do the same thing.
And don't buy Napa parts. They fit, they work, but the higher-quality Bosch stuff is available from site sponsors for less.
You may notice that at least one of those site sponsors has a Bentley 8 valve 900 repair manual. No endorsement: worth its weight in gold!
, Tue, 16 Jan 2007 21:16:43 <-- Viewing This Message
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