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TPS from 9.8% to 79.8% '98 C70 T5

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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mashinalens
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TPS from 9.8% to 79.8% '98 C70 T5

Post by mashinalens » Mon Jun 15, 2020 5:19 am

TP (%) readings with Foxwell NT301 are:
1. Ignition is on:
- 9.8% with closed throttle body
- 79.8% with manually wide open throttle body (fully depressed pedal shows 80.2%)
2. Idle:
- 9.8%
- I suppose the same 79.8%

MAF while idling: 3.95-4.4 g/s
RPMs while idling: 810-840

Fuel consumption in city: around 20 L/km (11.7 MPG)

Is this okay or I should change TPS?

In VIDA I found this:
TP V =% Throttle Potentiometer Position
Measuring range: 0-100% Normal value for throttle closed position: approx. 0%, Throttle fully open: approximately 100%. The transmission control module determines the degree of opening in % based on the signal of the throttle potentiometer.
I also feel a light kick of the gearbox at a speed of 20 km/h similar to a gear shift (but I know that the second gear should shift at 40 km/h on Economy mode)

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abscate
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Re: TPS from 9.8% to 79.8% '98 C70 T5

Post by abscate » Wed Jun 17, 2020 4:40 am

That’s really bad fuel economy , you should be getting at least 16 l/100km, but I wouldn’t change the throttle yet

Are your coils and plugs and air filter all new or under 30,000 k old?
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Re: TPS from 9.8% to 79.8% '98 C70 T5

Post by mashinalens » Wed Jun 17, 2020 1:56 pm

Clean PCV, new plugs (Bosch), new air filter, fuel filter, clean fuel injectors, changed vacuum tubes.

There is only one little air leak from air intake hose (part #9186200 now is arriving).

Unfortunately, I don't know about the condition of the coils, my mechanic told me nothing about them. The car starts with a half-turn.

When I start the cold engine there is a little white smoke from exhaust pipe and after a half of minute it's gone.

On the highway fuel consumption is about 7.5 L/100km.

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Re: TPS from 9.8% to 79.8% '98 C70 T5

Post by abscate » Wed Jun 17, 2020 2:53 pm

Read the tops and look at the date code

Format is YYWW where the first two digits are year of manufacture and the WW is the week, 01-52

Your highway mileage is excellent , that vacuum leak could be causing the loss of efficiency
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Re: TPS from 9.8% to 79.8% '98 C70 T5

Post by misha » Wed Jun 17, 2020 3:14 pm

Vacuum leak is your problem and spark plugs if they are not cheap Bosch copper plugs properly gapped.
Gap is critical on turbo engines.

That leak is messing with Maf and o2 sensors readings which results in higher fuel consumption.

In stop and go traffic with short distances...add there automatic transmission...mileage is about right.
16+l/100km,depending on how heavy the traffic is.
Fixing that vacuum leak will minimize the fuel consumption in city traffic.
Highway mileage is excellent...as abscate said.
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'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
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'71 144 S
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Re: TPS from 9.8% to 79.8% '98 C70 T5

Post by mashinalens » Thu Jun 18, 2020 1:54 am

Thank you guys. I'll look for the plug gap and change the air hose.

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Re: TPS from 9.8% to 79.8% '98 C70 T5

Post by misha » Thu Jun 18, 2020 2:02 am

After you replace the hose and correct gap(if it's not gapped correctly),remove negative battery cable for 15min to reset fuel trims.
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mashinalens
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / 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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