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I'll take a swing Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 1 Aug 2001 14:38:08
In Reply to: Figure this one, vacuum master., Michael Kaiser, Wed, 1 Aug 2001 11:22:27 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The only way base boost is limited by the CC is the pressure switch in-line with the APC solenoid. Now, going by my theory above, getting full boost when overriding the CC by pressing the gas means the pressure switch is working. After extensively checking the schematics, there is no RPM signal going into the CC.
Here's my take - the CC pump pulls vacuum, and that vacuum pulls the CC actuator. There has to be some controlled leak there - otherwise the CC pump could never release the throttle.
The actuator pulls on the throttle with a pull-chain. If you press the gas pedal down more than the actuator commands, the chain just goes slack.
I figure it's either one or both of the following - the 'controlled leak' isn't big enough, so it takes a long time for the pressure to bleed down enough to turn off the pressure switch, and/or the pressure switch is switching at too low a vacuum (close to atmospheric). Even if there is a small vacuum in the line, the actuator will be pulling on the chain a little, but you will be pressing the pedal down more and the chain will be slack. So you're controlling the engine speed, but the little bit of vacuum left in the line is keeping the pressure switch off, and keeping you in base boost.
All turning the CC on and back off does is put power to the CC pump. The pressure switch isn't electrically in that loop. Perhaps cycling power to the pump but not engaging the CC causes it to dump whatever remaining pressure there is in the system. I would think then that hitting the clutch or brake pedal would do the same - that would vent any vacuum left in the system.
If hitting the clutch or brake pedal for a second (not far, just a touch) gets you the same results as cycling the CC, I would think about replacing the pressure switch, mostly because it's the easiest to access and you could probably get a spare out of a junker cheap.
, Tue, 31 Jul 2001 22:17:11, Wed, 1 Aug 2001 14:38:08 <-- Viewing This Message
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