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95 850 Rough idle, needs 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
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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abscate
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Re: 95 850 Rough idle, needs gas

Post by abscate » Thu Feb 13, 2020 7:21 pm

You have to read the chart I linked to very carefully. Too carefully , actually

The columns are shifted so that the wrong numbers are aligned with the temperatures.

Awful.

I have to put a note on this in there

4K ohm at 10 C is close to spec
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Re: 95 850 Rough idle, needs gas

Post by ebbie » Fri Feb 14, 2020 4:37 am

So the ECT sensor should be working fine then?

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Re: 95 850 Rough idle, needs gas

Post by abscate » Fri Feb 14, 2020 7:29 am

ebbie wrote:
Fri Feb 14, 2020 4:37 am
So the ECT sensor should be working fine then?
Well , it has to work over the whole range, not just at a single point. The engine almost doubles the fuel injected at cold start, so if the resistance isnt right, it won't run.
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Re: 95 850 Rough idle, needs gas

Post by ebbie » Fri Feb 14, 2020 7:45 am

Hmm ok.. Would the best way of checking it be through taking it out and boiling it in water to see the temp and resistance? Or would it be enough to drive the car around for some time and checking the resistance then?

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Re: 95 850 Rough idle, needs gas

Post by RickHaleParker » Fri Feb 14, 2020 7:50 am

ebbie wrote:
Thu Feb 13, 2020 4:00 pm
If so, it was 4.38 so 4380 ohms when I checked.
Measured when it is not connected to the sensor or when it is plugged into the sensor?
Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0,
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Re: 95 850 Rough idle, needs gas

Post by erikv11 » Fri Feb 14, 2020 7:58 am

ebbie wrote:
Fri Feb 14, 2020 7:45 am
Hmm ok.. Would the best way of checking it be through taking it out and boiling it in water to see the temp and resistance? ...
Absolutely. Boil water, put the sensor in and check it, then turn off the heat and check the resistance at several points as it cools.
'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, 285k
'06 S60 R, 165k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

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Re: 95 850 Rough idle, needs gas

Post by RickHaleParker » Fri Feb 14, 2020 8:09 am

erikv11 wrote:
Fri Feb 14, 2020 7:58 am
Absolutely. Boil water, put the sensor in and check it, then turn off the heat and check the resistance at several points as it cools.
H2O melts at 0 °C (32 °F) therefore the drip off an Ice cube is 0 °C (32 °F).
Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0,
Plant Torslanda Sweden.
----------------------------------------------------------------
1997 S90, B6304S, AW30-42, Bosch Motronic 4.4 - Sold

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Re: 95 850 Rough idle, needs gas

Post by ebbie » Fri Feb 14, 2020 9:22 am

Alright then I will see if I can do that this weekend. Thanks for the guidance! :)

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Re: 95 850 Rough idle, needs gas

Post by erikv11 » Sat Feb 15, 2020 12:55 pm

RickHaleParker wrote:
Fri Feb 14, 2020 8:09 am
erikv11 wrote:
Fri Feb 14, 2020 7:58 am
Absolutely. Boil water, put the sensor in and check it, then turn off the heat and check the resistance at several points as it cools.
H2O melts at 0 °C (32 °F) therefore the drip off an Ice cube is 0 °C (32 °F).
Hi Rick, I find your statement of fact irrelevant. There is no doubt some clever intent behind your crypticness, please elaborate!
'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, 285k
'06 S60 R, 165k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

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Re: 95 850 Rough idle, needs gas

Post by ebbie » Sun Feb 16, 2020 11:05 am

Actually, I solved the problem! My mom started googling about my issue and came upon a post about the idle air control valve, where it had gotten stuck. I never really stopped thinking about the IAC, and so I checked on YouTube some people saying the IAC should make a little rattling sound if you shake it. I didn't remember it making any sound when I cleaned it a few days ago, so I went back to the IAC and decided to give it a couple of gentle hits to the valve, and tried to open it manually. Sure enough it opened up now! So I cleaned it again even more and then put some oil too to make it smooth, and ran the valve back and forth a couple of times. Car started perfectly!

I feel stupid for not having checked if the valve opened or not when I cleaned it th first time, I guess I was too nervous about poking around too much.

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