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That's quite backwards Posted by Ari [Email] ![]() ![]() In Reply to: Vacuum/Boost guage acting weird... and now no boost!, ebarter, Wed, 31 May 2006 15:45:24 Members do not see ads below this line. - Help Keep This Site Online - Signup |
At idle, the needle should be on the far left, in the vacuum range (Green?). The same for engine braking - it should be even farther to the left. Engine off, it should move up to atmospheric (the gap between green and yellow). Under boost - accelerating, especially under load (like up a hill ) it should go positive - into the yellow.
Depending on the year, vacuum is white or green. Boost is always yellow.
My first guess is that it isn't hooked up properly. In the engine compartment there is a three-way T junction - one hose to the APC solenoid, one to the intake manifold, and the last dives into the firewall and connects to the turbo gauge.
The Cruise control is tied into the turbo, but not quite that way. The vacuum pump (on the left fender) connects to a vacuum switch - it looks like a little disk, with two wires. One wire goes to the APC solenoid, the other to a wiring harness. When the CC is operating, it has vacuum, and that opens the switch and de-powers the APC solenoid. But that would be the same as a de-energized solenid, which should give you base boost (mid yellow).
Have you replaced the vacuum lines to the APC? Is it possible those are messed up? The W line goes to the wastegate actuator. The C line (compression) goes to the T with the intake manifold and boost gauge. The R line goes into the big hose on the intake side of the turbo.
I would do a complete review of the vacuum lines. Even if the line to the boost gauge had fallen off, you'd still have some boost.
Do you know you don't have boost because the gauge says so, or because the car is a complete dog? You may be boosting to some extent AND have a plumbing issue to the boost gauge.
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