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Hesitation and "missing" diagnosis Posted by dbreid [Email]  (#1192) [Profile/Gallery]
(more from dbreid) on Thu, 14 Jan 2010 10:38:14
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Firstly, this will probably be long, but I'll give you as much information as I can:
The Car___________________________
1993 Saab 9000 Aero 5spd w/TCS
185K, in generally excellent shape.
Has had almost everything replaced in the last two years of my ownership.
Brand new (OEM) DI cassette 1 year ago.
Running the proper NGK's (1 year ago)
All new headgasket work, all motor mounts, chains, pulleys, alternator, air cleaner, etc.
With the exception of the clutch and the shocks, I am running out of things that haven't been replaced. Normally, the car runs perfectly.
The Symptoms__________________________________________
I recently took a trip to Portlan OR from the Bay Area (up and back). Car ran perfectly, with one exception... It would "hesitate" under power sometimes. At first I wrote it off as being in the wrong( higher) gear on the steep passes, but I eliminated that.
Anyway, now it happens with more frequency. As best I can describe it, it feels like a miss. Not enough to cause the car to stall, of course, but if is low on poer, and kinda "Stumbles". As I press the accelerator, it will happen (the stumble) for maybe 1500 RPM, and then the car seems to "break through" and feel fine.
Facts:
1.) Doesn't matter if the car is warm or cold. Sometimes it happens immediately when I start the car. Sometimes not.
2.) Car boosts perfectly. All the way to the yellow/red hash marks.
3.) Can happen at idle.
4.) Doesn't appear to happen much above 4500 RPM, but I am not sure that means much, as it might just be masked at that point.
5.) When "it" isn't happening, the car feels perfect.
6.) TCS is not acting up.
7.) I have an ISAT if that will help me test. I haven't run the codes, because I am just thinking this through in my head in advance. But I will do that soon.
My Ideas and things I will test___________________________________
1.) Obviously, I am installing new spark plugs. I just ordered them, and they'll be here next week. Correct NGK's gapped to .9mm.
2.) I will look at vaccuum lines, because this is what my spider sense tells me is wrong.
3.) I ordered new PCV vaccuum check valves, PCV valve (the one that pulgs into the VC cover), and (just because I never replaced it) a red/white TCS valve.
4.) The DI cassette is nearly new, and looks fine. I have a spare, but it is on its last legs, and although the car will run with it in, it doesn't run well, so I do not have a perfect spare to eliminate the DI.
Other Thoughts?____________________________
Any suggestions of things to look for?
What vaccuum lines might be the culprit?
Thanks in advance.
-Dan
, Thu, 14 Jan 2010 10:38:14 <-- Viewing This Message, Sun, 17 Jan 2010 22:40:56, Tue, 19 Jan 2010 19:27:34, Tue, 19 Jan 2010 22:26:42, Wed, 20 Jan 2010 14:00:09, Mon, 18 Jan 2010 21:47:56, Thu, 14 Jan 2010 13:07:50, Thu, 14 Jan 2010 15:40:29, Thu, 14 Jan 2010 12:59:04, Fri, 15 Jan 2010 10:20:00
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