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PVC system

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

Volgrrr
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Year and Model: '95 T5 wagon
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PVC system

Post by Volgrrr » Sat Dec 26, 2009 9:16 pm

My '95 T5 has developed a distinct, annoying hesitation when the accelerator is depressed firmly. It then recovers and runs smoothly. Also when the accelerator is released, the engine seems to nearly cut out.

Also, when the vehicle first moves off, the instantaneous fuel consumption on the computer indicates the engine is using about 50 litres/100 kilometres and then when normal road speed is reached (i.e. 100 k.p.h) the consumption gradually drops down to about 25 litres/100 kilometres.

Then, after about 5-10 minutes the fuel consumption continues to drop until the vehicle is only consuming in the region of 7.8/8.3/100 kilometres and, over a full tank, averages about 9 litres/100 kilometres which, in my opinion, is quite acceptable.

Has anyone got any ideas what causes the initial atrocious fuel consumption in the first few minutes of operation? I wouldn't like to only drive about 15 kilometres per trip on a fairly constant basis because I would never be able to afford the fuel (luckily it does get better).

Beside the above fuel consumption the engine also hesitates quite noticeably on initial acceleration and does the same thing on deceleration.

My guess is the hesitation problem might be fuel related due to some item(s) that affect/control fuel supply not operating properly - but which one(s) and where?

Does anyone out there have any idea(s) what might be causing this irritating problem?


There are only two types of car owners - those who own Volvos and those who wish they did.

9394volvo850s
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Year and Model: 93 850 5spd 94 850T5
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Re: PVC system

Post by 9394volvo850s » Sat Dec 26, 2009 11:14 pm

you might want to do a tune up if its been a while. and also a fuel system cleaning with throttle body and air intake cleaner cant hurt. also pull the dipstick out check to see if you have smoke coming out of it at idle. if so the pcv may be cloged too.


93 850 5spd 320k (the daily)
94 850 T5 190K (race car)
95 T-5R wagon yellow (summer wag)
90 745 5spd 295k (winter wag)
67 122 2 door 4spd 69k :))

Volgrrr
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Re: PVC system

Post by Volgrrr » Sun Dec 27, 2009 5:03 am

I'm trying to systematically go through the various items that might possibly cause a fuel rich situation at acceleration and deceleration.

So far I've cleaned the MAF sensor and the injectors and changed the air cleaner.

The next thing I'm going to tackle is to thoroughly clean the throttle body to see if that makes any difference.

However, I've been wondering what symptom(s) a partially or fully blocked PVC system might show as well as what effect it might have on fuel consumption (hence the heading of the original post - even though I was side-tracked while writing the post and made no mention of it at all).

Also there is absolutely no sign of the sump being pressurised and the vehicle uses basically no oil between services.

So I guess it is just a matter of trial and error until I eventually find what is causing the problem or throw my hands up in despair.


There are only two types of car owners - those who own Volvos and those who wish they did.

valvster
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Re: PVC system

Post by valvster » Sun Dec 27, 2009 5:14 am

I'm thinking thermostat & coolant temperature sensor.
cheers...Valvster



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phils94850
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Re: PVC system

Post by phils94850 » Sun Dec 27, 2009 6:16 am

valvster... as posted, when was the last time you did a good tune-up on the car. Start off with the basics, and work your way on..


1996 Platinum Edition

Volgrrr
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Year and Model: '95 T5 wagon
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Volgrrr

Re: PVC system

Post by Volgrrr » Sun Dec 27, 2009 1:56 pm

Thanks for all the help so far - I appreciate it very much. The vehicle is due for its next service in about 300 kilometres (180 miles) and I will ask the garage to give it a full tune-up then.

Yes, I agree a faulty coolant temperature sensor would fit the bill (i.e. signalling the EMS the engine is still cold when it really is at normal operating temperature - initiating the EMS to respond by increasing the richness of the air to fuel mixture) however the temperature gauge in the cabin moves up to the 3 o'clock position and stays there without any variation once the engine is warmed up.

So, is it possible the cabin temperature gauge will indicate the engine is operating at normal temperature if the coolant temperature sensor is actually faulty?


There are only two types of car owners - those who own Volvos and those who wish they did.

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