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T5M bogs when getting off the gas

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
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Clemens
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T5M bogs when getting off the gas

Post by Clemens » Fri Sep 28, 2018 3:54 am

after getting a new rotor, distributor (bosch) and volvo spark plugs for my 94 T5M that annoying problem persist: when i get off the gas at lower or mid rpms and speeds the motor bogs once or twice. it is smooth under boost and mid throttle, quite smooth while cruising.
i thought it was spark related. but maybe it is fuel (fuel filter?) or vacum. the only thing i noticed is that the intercooler hose running to the intercooler was duct taped by the previous owner. it seems to hold pressure under boost, though.

any ideas?
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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Clemens
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Re: T5M bogs when getting off the gas

Post by Clemens » Fri Sep 28, 2018 11:49 am

anyone?
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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abscate
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Re: T5M bogs when getting off the gas

Post by abscate » Fri Sep 28, 2018 2:30 pm

he only thing i noticed is that the intercooler hose running to the intercooler was duct taped by the previous owner.
a tiny leak here will kill you..I would replace that hose ASAP.
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Clemens
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Re: T5M bogs when getting off the gas

Post by Clemens » Fri Sep 28, 2018 3:16 pm

thanks. i'll give it a try. sure cheaper than throwing other parts at it.
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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Clemens
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Re: T5M bogs when getting off the gas

Post by Clemens » Wed Oct 10, 2018 1:11 pm

got my new turbo to intercooler hose today and yes, even though the inner layer of the old hose appears not to be cracked, replacing it made a huge difference. seems like the damaged structural integrity of the old hose caused it to collapse and expand more than it should. it is still not silky smooth, so I will tackle the vacum hoses next.
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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abscate
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Re: T5M bogs when getting off the gas

Post by abscate » Wed Oct 10, 2018 1:50 pm

Whose got the Volvo Horns? I can claim them for a day...or until the 2004 I worked on - her owner figures out I foxtrotted her car...
1 SWMBO for 30 years
2 Volvos
3 VWs
4 Careers
5 cats/dogs/gears
6 Perfect Ladies in waiting
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1999 V70 T5M 56 2005 V70 NA M56 VWs BMW

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Re: T5M bogs when getting off the gas

Post by misha » Wed Oct 10, 2018 4:23 pm

Clemens wrote:
Wed Oct 10, 2018 1:11 pm
got my new turbo to intercooler hose today and yes, even though the inner layer of the old hose appears not to be cracked, replacing it made a huge difference....it is still not silky smooth, so I will tackle the vacum hoses next.
Reset ecu by removing negative battery cable for 10-15min in order to reset fuel trims.
Perform re-learn procedure and see is there any difference.
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'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
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Clemens
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Re: T5M bogs when getting off the gas

Post by Clemens » Thu Oct 11, 2018 12:52 pm

i will give it a try and report back
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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Clemens
Posts: 857
Joined: Thu Sep 03, 2015 12:34 pm
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Austria

Re: T5M bogs when getting off the gas

Post by Clemens » Fri Oct 12, 2018 10:08 am

i cleaned the maf and reset the computer. that did improve dribeability. then i swapped the ignition coil with the known good one out of my 96 R and that further improved things. I'm feeling sassy and might order the last pricey item, a set of bourgicord wires. might just be a cumulated tuneup issue.

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
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

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misha
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Re: T5M bogs when getting off the gas

Post by misha » Fri Oct 12, 2018 10:55 am

I had never seen them failed.
I bought the car new and still have original wires...not a hiccup...never.
Drive it a bit allowing an ecu to fine tune itself.After reset it needs a good few hundred kms to set new fuel trims and to re-learn new inputs from all sensors.
'97 850 2.5 20v /fully equipped/ Motronic 4.4 / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
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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