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97 850 Hissing and Rough Idle Topic is solved

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

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dairyqueen814
Posts: 186
Joined: Mon Jul 01, 2013 2:43 pm
Year and Model: 1997 855 NA
Location: Worcester MA

97 850 Hissing and Rough Idle

Post by dairyqueen814 »

Hi guys
Really quick, hopefully simple problem. I've got a constant hissing going on and I'm almost positive its a vacuum leak. The car is wonky when idling and the idle almost chokes out when I'm braking. There is no leak at the tree and I just want to get an opinion before taking off my manifold to poke around. I know the vacuum system is relatively simple on my car and I might just need to clean/replace the PCV as it hasn't been done in 50k miles.
Also maybe unrelated my throttle sticks closed the tiniest amount. I think I just need to spray carb cleaner in the throttle body because I know the flame trap is right there and might have a bit of goop leaking in.

Anyway thanks in advance!
1994 850 Sedan NA Black, 343,000mi - Crashed and parted
1993 850 Sedan NA Red, 240,000mi - Now my little brother's car
1994 850 Wagon NA White, 251,222mi - Sold
1997 850 Wagon NA Red, 105,000mi - Currently my pride and joy
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theWIFES_S70
Posts: 1172
Joined: Fri Jul 24, 2015 10:34 pm
Year and Model: 1998 S70 base
Location: Queens, New York
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Re: 97 850 Hissing and Rough Idle

Post by theWIFES_S70 »

The only lines connected to the braking system are the brake booster vacuum hose and the brake booster check valve. Sounds like it could be coming from there. Take some pictures for us and let us take a gander!
1998 Volvo S70, N/A, 5-speed, 185K
2007 Volvo S40, 2.4i, 5-speed, 100K
dairyqueen814
Posts: 186
Joined: Mon Jul 01, 2013 2:43 pm
Year and Model: 1997 855 NA
Location: Worcester MA

Re: 97 850 Hissing and Rough Idle

Post by dairyqueen814 »

I'll try sometime this week. I know the car backwards and forwards it's just a matter of time spent chasing gremlins that I don't have anymore. Thanks for the direction!
1994 850 Sedan NA Black, 343,000mi - Crashed and parted
1993 850 Sedan NA Red, 240,000mi - Now my little brother's car
1994 850 Wagon NA White, 251,222mi - Sold
1997 850 Wagon NA Red, 105,000mi - Currently my pride and joy
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erikv11
Posts: 10041
Joined: Sat Jul 25, 2009 2:03 pm
Year and Model: 850, S/V70, 06 S60R
Location: Iowa
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Re: 97 850 Hissing and Rough Idle

Post by erikv11 »

Big fat brake booster line, easiest way to check it on an NA is to pull the battery. You don't need to pull the manifold just yet, save yourself the hassle if you can. Replace with any thick walled vacuum line, I have used silicone there.

On the throttle plate you are on track. Pull the ducting to the throttle while you are checking the brake booster, spray some carb cleaner on a rag, wipe it out real well.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 293k
'06 S60 R, 167k
'99 Camry V6 :shock: 130k
gone: '96 NA 850 210k, '98 NA V70 182k
dairyqueen814
Posts: 186
Joined: Mon Jul 01, 2013 2:43 pm
Year and Model: 1997 855 NA
Location: Worcester MA

Re: 97 850 Hissing and Rough Idle

Post by dairyqueen814 »

Awesome I'll give it a go this week. Will report back either way.
1994 850 Sedan NA Black, 343,000mi - Crashed and parted
1993 850 Sedan NA Red, 240,000mi - Now my little brother's car
1994 850 Wagon NA White, 251,222mi - Sold
1997 850 Wagon NA Red, 105,000mi - Currently my pride and joy
dairyqueen814
Posts: 186
Joined: Mon Jul 01, 2013 2:43 pm
Year and Model: 1997 855 NA
Location: Worcester MA

Re: 97 850 Hissing and Rough Idle  Topic is solved

Post by dairyqueen814 »

So yesterday I was hunting down the sound. I checked all my vacuum lines, everything was fine but I couldn't inspect the lines behind the manifold. I have the Snabb intake spacer so I just popped off the manifold to check..... well the manifold came off and as it turns out the Snabb spacer rotted out and was pissing air. Seriously? The part I bought so I wouldn't have to worry about replacing it was ruined. Long story short, after 2 hours of driving around to different Volvo dealerships who thought they had a gasket but didn't.... In a summer car.... getting dirt all over it... But it's fixed now.

Thanks all!
Now I just have to find the clunk in the rear end..
1994 850 Sedan NA Black, 343,000mi - Crashed and parted
1993 850 Sedan NA Red, 240,000mi - Now my little brother's car
1994 850 Wagon NA White, 251,222mi - Sold
1997 850 Wagon NA Red, 105,000mi - Currently my pride and joy
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