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Hello! I bought a 1990 5-speed hatchback 900 two weeks ago. I purchased it knowing it was not yet roadworthy. Its a great car, no rust as it spent most of its life in Texas. It has a few dash cracks and a saggy headliner, but those cosmetic issues aside, its very clean. 90,000 original miles.

The owner informed me that the car would start and idle for a few minutes, then lose power and eventually stall. I finally got under the hood over the weekend. I started it, and it ran well enough. Started in about 2 cranks and idled around 900 rpm. In about 2 minutes it began to rev and drop, hitting about 1300, and dropping to about 500 rpm. It was clattering, it was loud. The rhythm followed the engine speed. I shut it off, removed the valve cover and cams. The three lifters on the intake side, at the back of the engine (front of car) were squishy. I didnt measure, but I would say they pushed in about 1/4 inch. All others held firm.

I looked through a few other threads in the C900 forum, related to lifter problems, and the consensus seems to be to use a fully synthetic, lighter weight oil before replacing lifters. Some said try additives such as lucas, others said not to. I will try a fully synthetic oil this coming weekend, any recommendations?

I am no car expert, but I enjoy working on them and researching issues. My idea is that the computer is enriching the mixture because of the failing intake lifters. As the engine warms and the idle lowers I am thinking the over-enriched mixture, combined with the three failing lifters are causing all my mechanical issues. It would be great to have some insight from others with more experience. If anyone needs more information, please ask. Thanks in advance!

- Jim
 

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Typically, loud lifters on a Saab will work themselves out after several minutes of running.

I'd start by looking for vacuum leaks, the symptoms you describe could very well be caused by them. I'd also check your NTC sensor (between the middle fuel injectors), which should be measured in resistance, not voltage and also check the O2 sensor output. Check the plugs, rotor, distributor, wires and if it's a turbo check the timing.
 

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Add to the previous post, the AIC valve. But before you do any of that, have you got oil pressure? The release valve could be stuck open. It does happen. With no oil pressure you will get very noisy lifters and it won't go away, apart from the damage occurring in the rest of the engine. Does the oil light come on when the ignition is on without starting the engine? Does it go out when you start the engine? If you get no oil light with ignition on, don't start the engine again. The bulb may be gone. Fix that before anything else.
 

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And a now show on the oil light could be a pressure switch. A simple test in that case is to earth the wire to the oil pressure switch to the body with the ignition on.
 
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