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Re: 9000 Turbo - 1987 SAAB, Electrical Diagrams - Emmision Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 24 Jan 2005 10:06:24
In Reply to: 9000 Turbo - 1987 SAAB, Electrical Diagrams - Emmision, Herman, Mon, 24 Jan 2005 09:45:52 Members see ZERO ads on the bulletin boards and get more feature. - Help Keep This Site Online - Signup |
First off, the MAF (Air Mass Meter - AMM) adjustment is screwing you up.
The 380 ohm setting is an INITIAL setting only - usually good enough to get the engine to run. You then adjust the screw until you get the O2 sensor to swing back and forth, from about 0.2 to about 0.9. The critical point is to adjust the screw so that the O2 signal spends 50% above 0.5 volts, and 50% of the time below 0.5 volts. Whatever the end result resistance setting is fine.
It seems that under any load, you're going lean - that's the O2 sensor stuck on 200 mv. The fact that the fuel pressure is increasing is a good sign - it should be. My guess is that the spark plugs look lean.
The only things that control mixture are the O2 sensor and the AMM (MAF). The AMM has 100% authority over fuel, and the O2 sensor only 25%.
What you didn't say was how it failed emissions. If it were running lean, I'd expect the NOx to be way out, but the HC probably OK. If it is indeed running lean (high NOx, plugs showing lean), I would suspect either a vacuum leak on the engine side of the AMM, or a bad AMM. About all you can do on the AMM is to replace it - rebuilt units run about $150.
An important place to check for a vacuum leak is the evaporative charcoal canister. It's mounted in the right front fender, where you can't see it. It has a thin hose running to the throttle body to control the Purge valve, and a fat hose running to a takeoff on the intake plenum for the vapors. Quite often with turbo cars, the pressure blows the hose off the canister, and you don't see it because it's hidden in the fender. Remove the right front turn signal and look in - make sure the hoses are still in place.
As a test, you can try plugging both the thin Purge Valve hose and the fat supply hose from the canister, and see if that cleans up both the idle and the emissions.
posted by 192.249....
, Mon, 24 Jan 2005 10:06:24 <-- Viewing This Message
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