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Low vacuum at idle...

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.
1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70
shawneesnaketail
Posts: 11
Joined: Wed Apr 10, 2019 6:09 pm
Year and Model: 1995 850T Wagon
Location: Arizona
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shawneesnaketail

Low vacuum at idle...

Post by shawneesnaketail » Wed Apr 10, 2019 6:20 pm

Hello all! This is my first post, but I can assure you I have been lurking for many years. I appreciate all of the insight this forum has to offer.

My question is regarding low vacuum in general according to my aftermarket boost gauge (Equus). At idle in park, it reads at 13inHg, when car is put into D or R, it goes down to 10inHg. The boost gauge reads 10PSI of boost at WOT. What could cause this low vacuum reading? I have tested for vac leaks to the best of my ability with carb cleaner and have found none. Something I have noticed is that my brake pedal makes a "whoosh" sound when depressed and this affects the vacuum by about .5inHg. If it is of any importance, I am between 5500 and 6000ft elevation in Northern AZ.

I have recently done a full timing service, serpentine belt, fuel filter, PCV overhaul (passed glove test), cap and wires (couldn't get old rotor off, gonna have to revisit that), air filter, and replaced some vac lines. Compression results are between 156 and 160 across all 5 cylinders. Could it be a timing issue? I have yet to check timing since I initially replaced the belt.

Thanks!
Last edited by shawneesnaketail on Wed Apr 10, 2019 6:26 pm, edited 1 time in total.



shawneesnaketail
Posts: 11
Joined: Wed Apr 10, 2019 6:09 pm
Year and Model: 1995 850T Wagon
Location: Arizona
Has thanked: 1 time
Been thanked: 3 times
United States of America
shawneesnaketail

Re: Low vacuum at idle...

Post by shawneesnaketail » Wed Apr 10, 2019 6:23 pm

One more thing! I have noticed that this particular wagon seems to be low on power in the lower RPMs. It seems like the RPMS take a lot longer to rise than on my NA 850.. Thanks



tardcart
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Joined: Fri Feb 08, 2019 4:17 pm
Year and Model: 96 850t. 93 940t
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tardcart

Re: Low vacuum at idle...

Post by tardcart » Wed Apr 10, 2019 6:49 pm

sounds like your car is perfect. are you experiencing rough idle? NA are faster till shit hits the fan turbo wise.



tardcart
Posts: 205
Joined: Fri Feb 08, 2019 4:17 pm
Year and Model: 96 850t. 93 940t
Location: Pittstown Nj
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tardcart

Re: Low vacuum at idle...

Post by tardcart » Wed Apr 10, 2019 7:05 pm

a common problem is the turbo compressor bypass valve leaks. suck on the line to it and you should not be able to move any air. You would lose some vac there with out knowing it. If you can suck air then you need a new diaphragm. IPD has them. Volvo doesnt.
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