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Volvo AWD 850 Forum

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12 in vacumm, drops to 10in at 4000rpm. 850 1995

posted by  KlausC on  Mon Dec 7 13:46 CST 2015
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last visit: Fri Oct 24 10:15 CST 2014
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I found this in my 850 online owner's manual for diagnostics:

Exhaust System Backpressure
1) Exhaust system can be checked using a vacuum or pressure gauge. Remove oxygen sensor or air injection check valve (if equipped).
2) Connect a 1-10 psi pressure gauge, and run engine at 2500
RPM. If exhaust system backpressure is greater than 1 3/4-2 psi, exhaust system or catalytic converter is plugged.
3) If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steadily. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for a restriction.

So your car sounds "normal". I would expect slightly less vacuum with the butterfly valve open and allowing more air into the intake.

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Keeping it running is better than buying new






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New Suspecting backpressure in exhaust. Good place for vacumm ck or diag. [850][1995]
posted by  Three5bangers  on Sun Dec 6 12:24 CST 2015 >


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