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T5M bogs when getting off the gas

Help, Advice and DIY Tutorials on Volvo's P80 platform cars -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, including 850 R, 850 T-5R, 850 T-5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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Clemens
Posts: 1932
Joined: 3 September 2015
Year and Model: 96 855 R + 94 855 T5
Location: Austria
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Re: T5M bogs when getting off the gas

Post by Clemens »

alright. if it takes that long i might just pour a bottle of injector cleaner into the fuel tank and drive. and maybe replace the fuel filter. most probably still the original one.
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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misha
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Post by misha »

Clemens wrote: 12 Oct 2018, 11:11 ... and maybe replace the fuel filter. most probably still the original one.
That's is NOT good....it should be replaced between 50-100k km.
That's how i'm doing it.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

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misha
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Post by misha »

Clemens wrote: 12 Oct 2018, 10:08 ...edit: what's left feels basically like small misfires at steady rpms between 2 and 3k. Snooth under boost, alright when getting off the gas
I missed this on previous reply...are turbo models have intake air temperature sensor(IAT sensor)?

If not....i'm guessing that you have small vacuum leak somewhere.

I'm assuming that you don't have DTC stored or pending.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

User avatar
Clemens
Posts: 1932
Joined: 3 September 2015
Year and Model: 96 855 R + 94 855 T5
Location: Austria
Has thanked: 473 times
Been thanked: 219 times

Post by Clemens »

No CEL. I had one showing a long term fuel trim issue when I bought it 2 years ago. After deleting it, it never returned. I searched for leaks thoroughly, couldn't find any. Maybe around the fuel injectors. would it be safe to spray the fuel injector seals with brake cleaner?
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

User avatar
misha
Posts: 5379
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Year and Model: '97 850 2.5 20v
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Post by misha »

I'm not sure about brake cleaner onto injector's o-rings.
What about IAT?
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

User avatar
Clemens
Posts: 1932
Joined: 3 September 2015
Year and Model: 96 855 R + 94 855 T5
Location: Austria
Has thanked: 473 times
Been thanked: 219 times

Post by Clemens »

from what I have read only cars 99 and up have that sensor. i will doublecheck tomorrow and try to read if any codes are stored even though no cel is on
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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misha
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Year and Model: '97 850 2.5 20v
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Post by misha »

Being a '94 you will have just obdI diagnostic ports under the hood.

Some codes will not turn on check engine light but they will be stored in ecu fault memory.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

User avatar
Clemens
Posts: 1932
Joined: 3 September 2015
Year and Model: 96 855 R + 94 855 T5
Location: Austria
Has thanked: 473 times
Been thanked: 219 times

Post by Clemens »

no codes stored in A2 (fuel system) and I can't get a signal from A6 (ignition) from the blinky box.
the lighter the throttle input, the worse it is. gotta look for vacum leaks again
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

User avatar
misha
Posts: 5379
Joined: 7 December 2008
Year and Model: '97 850 2.5 20v
Location: Serbia
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Post by misha »

If fuel filter isn't replaced recently,like you said....i would replace it first.
What about spark plugs...being a turbo car....are they properly gapped?It is pretty important for turbo engine.
Ignition ecu should be also scanned for codes...could be that there is a problem...somewhere...and CEL being OFF doesn't necessarilly mean that there are not codes stored.
Maybe IT is the source of the problems you're experiencing.
That said....not being able to communicate with it....could be that there is a problem.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

User avatar
Clemens
Posts: 1932
Joined: 3 September 2015
Year and Model: 96 855 R + 94 855 T5
Location: Austria
Has thanked: 473 times
Been thanked: 219 times

Post by Clemens »

plugs are new volvo, gapped correctly. maybe ignition wires. the ones on my 95 na went bad after 19 years, the ones on my 96R after 20. in this car they are from 94, one being a different length, looks like from the junkyard or sthg.
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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