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Re: 1990 900 T turbo acceleration abortion Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Fri, 2 Jan 2009 15:24:11 In Reply to: 1990 900 T turbo acceleration abortion, blue saab, Fri, 2 Jan 2009 12:36:34 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Where is the boost gauge going in all of this? Is it going to the end of the yellow, and then suddenly cutting back to the middle of yellow? Or is it going well into the red, and then suddenly cutting back from there?
When you get the cutoff, is it rather abrupt, almost violent? Or does it just stop pulling?
The unknown here is how much boost you're pulling, and what may or may not have been done to the car beforehand. For example, if it is boosting to the very edge of yellow and just touching the red, and then cutting back to about mid-yellow, that's the APC detecting knock and cutting back on boost. If it just goes to the edge of yellow/red, then cuts back a little, that is boost taper, which is normal.
If you're boosting well into the red, that's too much. Either the car was modified, or something isn't working right. There is no overboost pressure switch on a '90, but the LH will cut off fuel if the boost gets too high, based on other inputs. It's possible that you're hitting the overboost limit. That would be a more violent cutback, and it would occur with the needle well into the red.
So-
Does the boost gauge work?
When it cuts back, where is the boost gauge? Where does the needle cut back to?
Is it merely a drop-off in the acceleration, or does it feel like the engine quits?
Does the engine start to miss at full boost? (check plug gap and spark plug wires)
posted by 76.221.218...
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