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Plugs Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Sun, 12 Apr 2009 04:46:42
In Reply to: 1995 Saab 9000CS Stutter Problem, Bobby Peare, Sat, 11 Apr 2009 12:41:02 Members do not see ads below this line. - Help Keep This Site Online - Signup |
As the others have noted, start with the spark plugs. the CS is still a turbo engine, and if the spark plug gap is too big due to age and wear, the spark can't jump under boost (which happens under acceleration), and you get hesitation and miss.
So replace the spark plugs with the EXACT NGKs SPECIFIED IN THE MANUAL (I can't emphasize that enough!), gapped per the spec. As the others have noted, replace the air filter if it's tired - basically a tune up.
You may also have a DI (Direct Ignition cassette) problem. But before you toss it out and get a new one, do some checking. When you pull the old spark plugs, look for signs of arcing on the top of the old plugs - black marks, little holes, etc. Next, flip the DI over, and remove the 8 or so Torx screws holding the bottom on. Grab a teat and pull up. The plastic cover will pull off. Look for signs of arcing (black soot) on the metal face of each of the four coils (cylinders).
Why? There is a spring that touches both the coil face and the top of the spark plug, contained in each of the long bits (teats) on the bottom of the DI. If the spring gets tired, it doesn't make good contact. If it doesn't make good contact, it's the same as too big a spark plug gap. You can easily take a needle nose pliers and (gently) pull on the spring to lengthen it a little bit so it makes a good connection.
While the cover is off, hold the DI up to a light and look at each coil. They're opaque, but you should be able to see the level of fluid (oil) in each one. They should be 90% full. If one or more is leaking fluid (say 50% full) the DI needs to be replaced. Also look for signs of burning on the DI circuit board - which yes, is covered with potting compound (plastic - not soil for house plants). Look for obvious stuff. A burned circuit board means the DI needs replacement.
If the old spark plugs looked a harsh white, then the engine is running lean. Look for vacuum leaks - look for hoses that are cracked, or have just plain fallen off. Follow each hose to make sure it goes somewhere, and look for metal nipples that have a little ring of rubber, but no hose.
After a basic tune-up - the right plugs with the right gap, new air filter (when was the last time the fuel filter was replaced?), a quick DI and hose inspection, then see if you need to go to something more esoteric like a bad CPS.
posted by 76.225.184...
, Sun, 12 Apr 2009 04:46:42 <-- Viewing This Message
, Sat, 11 Apr 2009 22:41:37
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