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Boost Problems: Some Somewhat Esoteric APC Questions
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Posted by Craig [Email] (more from Craig) on Mon, 10 Mar 2003 22:38:06 Share Post by Email
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I’ve got an ‘87 9kT that hasn’t been boosting correctly lately. It boosts up to about where it should, then quickly tapers to at or near base boost. This isn’t the up/down fluctuational decrease I’ve seen before with knock, but just a quick and steady taper. Base boost is in spec. Here are some observations I’ve made, hopefully someone can tell me whether they are normal or not.

On the APC solenoid, C and R are closed to each other and W and C are open to each other when not energized, I understand that this is normal. However, ALL ports are open to each other when energized, is this normal?

I also applied pressure to the pressure transducer with a vacuum pump, which made the APC chatter at 3.5-4psi, well below the .5bar (7.5psi) spec on the Townsend site. It also sometimes takes a while to stop chattering when I release pressure. Could any of this cause my problem?

I also applied pressure to the wastegate actuator, which seemed to operate the wastegate as it should. However, the actuator would bleed off pressure at a moderate rate. The hose it fine. Is this normal, could it result in my boost taper problem?

Thanks a lot for any help guys!

Craig
‘87 9kT 265k

posted by 12.93.22...

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