Saab: Saab 900s sputtering., vacuum leaks, manifold vacuum

Question
Hi! I recently purchased a 1996 900s and when I give it some gas it seems to buck and sputter. I immediately changed the fuel filter and it appears the wired were changed recently. When I replaced the fuel filter, that took care of some of the problem. It now seems localized to when the car gets warm. Operates fine cold. Any suggestions?

Answer
The problem can be many things, but most likely, it's a vacuum leak somewhere. When the engine is cold, the fuel air ratio is relatively rich, so that the effect of the leak is masked. But when things heat up, the fuel air ratio gets smaller, to the precise point of maximum efficiency and minimum emissions. At this point, any air intake manifold (vacuum) leaks will have a noticeable effect, as you describe. An easy way to determine the site of such leaks is to spray starting ether (away from the air intake) all around the engine, particularly at hoses, places where two surfaces meet, etc., where any such leaks may occur. If the engine momentarily speeds up, that suggests the site of the leak...the vacuum has sucked in the ether mist and raised the engine rpm's.
  If this does not help, then you need to look for either electrical or temperature sensor malfunctions...lotta possibilities!
        hope this helps....................................