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S70 2.5t misfire

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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misha
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Re: S70 2.5t misfire

Post by misha » Sat Feb 01, 2020 11:16 am

radek93 wrote: ↑
Sat Feb 01, 2020 7:42 am
...It was like this before lpg assembly
Before LPG installation?
'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

radek93
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Re: S70 2.5t misfire

Post by radek93 » Sat Feb 01, 2020 4:13 pm

misha wrote: ↑
Sat Feb 01, 2020 11:16 am
radek93 wrote: ↑
Sat Feb 01, 2020 7:42 am
...It was like this before lpg assembly
Before LPG installation?
Yes

radek93
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Re: S70 2.5t misfire

Post by radek93 » Sat Feb 01, 2020 4:14 pm

michael8888 wrote: ↑
Sat Feb 01, 2020 9:18 am
I found after going over a year with the same issue and replaced everything that the culprit was the thermostat sensor that's at the thermostat housing. A $13 part plus a new thermostat while I was there. ECU reads the temp wrong from the sensor and adds more fuel to the mix to cool the temp.
Also, check that all electrical connections are good and clean. use some dielectric grease. Be sure the wires from the cam sensor are not near the ignition wires. that may cause some em feedback.
I have new temperature sensor

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wizechatmgr
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Year and Model: 1999 V70 XC AWD 2.4T
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Re: S70 2.5t misfire

Post by wizechatmgr » Sat Feb 01, 2020 6:50 pm

Did you verify the new parts were good before installation personally? Specifically the Crankshaft sensor & Camshaft sensor - test them again

Occasionally new parts aren't within spec. Bad batches do happen... Sometimes the longevity of a part isn't what it used to be. Also test the supply voltages to sensors and their grounds. Either having an issue will make the ECU go nuts.

Have you checked and verified the voltage at the ECU? These cars get pissy if the voltage isn't within spec.
Wisdom requires knowledge as a prerequisite, but knowledge can be developed due to a lack of wisdom.
In order to learn how to fix something, you must first learn how to break it.
1999 V70 XC AWD - ~187k miles

radek93
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Re: S70 2.5t misfire

Post by radek93 » Sun Feb 02, 2020 2:13 am

wizechatmgr wrote: ↑
Sat Feb 01, 2020 6:50 pm
Did you verify the new parts were good before installation personally? Specifically the Crankshaft sensor & Camshaft sensor - test them again

Occasionally new parts aren't within spec. Bad batches do happen... Sometimes the longevity of a part isn't what it used to be. Also test the supply voltages to sensors and their grounds. Either having an issue will make the ECU go nuts.

Have you checked and verified the voltage at the ECU? These cars get pissy if the voltage isn't within spec.
I have not verified. I put on good substitutes. Delphi and Hella. I improved the grounding of the entire car, also ecu. I checked the resistance of the ecu power cables. The only thing that surprises me is why, even after changing the alternator voltage regulator, finally replacing the alternator with a used one, the charge is still around 13.7-13.9 volts. Usually cars have a charge around 14.4 volts.

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misha
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Re: S70 2.5t misfire

Post by misha » Sun Feb 02, 2020 2:48 am

13.7-13.9v at idle with headlights,heater blower(not on 4th speed) and radio is OK.
Check voltage output directly on alternator b+ and it's casing.
If it doesn't match with battery terminals....cables are bad and voltage drop test should be performed on both....positive and negative side.
'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

radek93
Posts: 15
Joined: Sat Dec 07, 2019 2:43 pm
Year and Model: S70 98
Location: Home
Has thanked: 0
Been thanked: 0
Poland
radek93

Re: S70 2.5t misfire

Post by radek93 » Sun Feb 02, 2020 3:15 am

misha wrote: ↑
Sun Feb 02, 2020 2:48 am
13.7-13.9v at idle with headlights,heater blower(not on 4th speed) and radio is OK.
Check voltage output directly on alternator b+ and it's casing.
If it doesn't match with battery terminals....cables are bad and voltage drop test should be performed on both....positive and negative side.
I have so much without anything turned on. With the lights on etc. I have around 200-300 mv less. Wires, of course, checked. Even as a control I added ground and b + to the battery.

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misha
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Year and Model: '97 850 2.5 20v
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misha

Re: S70 2.5t misfire

Post by misha » Sun Feb 02, 2020 3:31 am

Check on alternator directly.
If the reading is the same as on battery terminals....voltage regulator is the culprit.
If battery terminals reading is lower than reading on alternator...then cables are bad.

Difference should not be higher than 0.2V.

Do this after driving around 30min and without turning the engine off.
This will allow you to have precise picture of what is going on...when cables and everything under the hood is warmed.

When cables are cold...the readings will be higher than real untill ressistance builds up....and will not give you real results.
'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

radek93
Posts: 15
Joined: Sat Dec 07, 2019 2:43 pm
Year and Model: S70 98
Location: Home
Has thanked: 0
Been thanked: 0
Poland
radek93

Re: S70 2.5t misfire

Post by radek93 » Tue Feb 11, 2020 1:08 pm

I checked everything. It looks ok. Only after removing the ignition cap did I notice that the distributor's finger had a burn mark from a spark under a metal element, on plastic. As if the spark leaped at the very end.

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wizechatmgr
Posts: 1317
Joined: Thu Jan 12, 2017 1:07 pm
Year and Model: 1999 V70 XC AWD 2.4T
Location: Albany, NY area
Has thanked: 22 times
Been thanked: 53 times
Contact:
United States of America
wizechatmgr

Re: S70 2.5t misfire

Post by wizechatmgr » Sat Feb 15, 2020 10:13 am

radek93 wrote: ↑
Tue Feb 11, 2020 1:08 pm
I checked everything. It looks ok. Only after removing the ignition cap did I notice that the distributor's finger had a burn mark from a spark under a metal element, on plastic. As if the spark leaped at the very end.
Sounds like a carbon track. This could have caused intermittent or consistent misfiring. I used to have a hell of a time keeping the distributor cap in my old VW dry. Eventually I used dielectric grease around the seal and at all electrical connections.
Wisdom requires knowledge as a prerequisite, but knowledge can be developed due to a lack of wisdom.
In order to learn how to fix something, you must first learn how to break it.
1999 V70 XC AWD - ~187k miles

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