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Another cold start rough idle post.

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
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callahanoffroad
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Another cold start rough idle post.

Post by callahanoffroad » Mon Feb 18, 2019 6:09 am

1994/5 Volvo 850 non turbo, manual transmission.

Okay I'm pulling my hair out here. Car is idling rough at idle when it's cold. Basically I have to start it and rev it for about 30 seconds or else it dies. Once even slightly warm it idles fine. So far I've replaced the following components trying to chase this:

Mass airflow sensor (oem Bosch)
Plugs
Wires (bougicord)
Cap and rotor (oem Bosch)
Vacuum lines are all new
PCV replaced 5000 miles ago

Only thing I can think of next is the idle air control valve. Those things are not cheap either. Is there a proper way to test them? I cleaned mine about this time last year.

Power band is still strong. I have no codes.

I offer my supplications to my Volvo brain trust. :D


Author, Chef, and Shade Tree Mechanic

1995 Volvo 850, Non-Turbo, VVIS, LH FI, Green, 215,000 miles. B5254FS engine. Herman. viewtopic.php?f=1&t=84393

1996 Volvo 850, died at 280,000

Founder of: CookingForChemo.Org

Chuck W
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Chuck W

Re: Another cold start rough idle post.

Post by Chuck W » Mon Feb 18, 2019 6:22 am

Have you checked your ECT sensor and connector?



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callahanoffroad
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callahanoffroad

Re: Another cold start rough idle post.

Post by callahanoffroad » Mon Feb 18, 2019 6:38 am

Chuck W wrote:
Mon Feb 18, 2019 6:22 am
Have you checked your ECT sensor and connector?
No I haven't and I'm not actually sure how to do that 😅


Author, Chef, and Shade Tree Mechanic

1995 Volvo 850, Non-Turbo, VVIS, LH FI, Green, 215,000 miles. B5254FS engine. Herman. viewtopic.php?f=1&t=84393

1996 Volvo 850, died at 280,000

Founder of: CookingForChemo.Org

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callahanoffroad
Posts: 248
Joined: Mon Jun 30, 2014 5:25 pm
Year and Model: 1995 850
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callahanoffroad

Re: Another cold start rough idle post.

Post by callahanoffroad » Mon Feb 18, 2019 7:51 am

Here's everyone's favorite thing...

A video!



Author, Chef, and Shade Tree Mechanic

1995 Volvo 850, Non-Turbo, VVIS, LH FI, Green, 215,000 miles. B5254FS engine. Herman. viewtopic.php?f=1&t=84393

1996 Volvo 850, died at 280,000

Founder of: CookingForChemo.Org

Chuck W
Posts: 150
Joined: Wed Dec 24, 2014 10:45 am
Year and Model: 97 854 T5
Location: Indianapolis, IN
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Chuck W

Re: Another cold start rough idle post.

Post by Chuck W » Mon Feb 18, 2019 8:07 am

The ECT is located in the base of the thermostat housing.

Any corrosion on the connector can cause issues, especially when it gets colder. Might not be your issue, but it's an easy thing to check and rule out.
Mine didn't act up until the temps got really cold and made the car run like crap. I cleaned the pins up a bit and it's been fine since.
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callahanoffroad



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callahanoffroad
Posts: 248
Joined: Mon Jun 30, 2014 5:25 pm
Year and Model: 1995 850
Location: St. Louis Missouri
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callahanoffroad

Re: Another cold start rough idle post.

Post by callahanoffroad » Mon Feb 18, 2019 8:53 am

Chuck W wrote:
Mon Feb 18, 2019 8:07 am
The ECT is located in the base of the thermostat housing.

Any corrosion on the connector can cause issues, especially when it gets colder. Might not be your issue, but it's an easy thing to check and rule out.
Mine didn't act up until the temps got really cold and made the car run like crap. I cleaned the pins up a bit and it's been fine since.
Sprayed it down with maf cleaner, its now idling a little better. Not perfect but much smoother. That's such a weird thing to cause an issue


Author, Chef, and Shade Tree Mechanic

1995 Volvo 850, Non-Turbo, VVIS, LH FI, Green, 215,000 miles. B5254FS engine. Herman. viewtopic.php?f=1&t=84393

1996 Volvo 850, died at 280,000

Founder of: CookingForChemo.Org

Chuck W
Posts: 150
Joined: Wed Dec 24, 2014 10:45 am
Year and Model: 97 854 T5
Location: Indianapolis, IN
Has thanked: 9 times
Been thanked: 12 times
United States of America
Chuck W

Re: Another cold start rough idle post.

Post by Chuck W » Mon Feb 18, 2019 8:58 am

callahanoffroad wrote:
Mon Feb 18, 2019 8:53 am

Sprayed it down with maf cleaner, its now idling a little better. Not perfect but much smoother. That's such a weird thing to cause an issue
Sprayed the connector down? I'd hit the male pins with some sandpaper, if you didn't do that.

I was surprised about the night/day difference on my car. It acted like it was running on 3 cylinders and wouldn't run for crap, even after all of the "Stage 0" stuff. Cleaned up the connector pins, and *bam*, it was running perfect.



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WhatAmIDoing
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Re: Another cold start rough idle post.

Post by WhatAmIDoing » Mon Feb 18, 2019 10:09 am

callahanoffroad wrote:
Mon Feb 18, 2019 6:09 am
1994/5 Volvo 850 non turbo, manual transmission.

Okay I'm pulling my hair out here. Car is idling rough at idle when it's cold. Basically I have to start it and rev it for about 30 seconds or else it dies. Once even slightly warm it idles fine. So far I've replaced the following components trying to chase this:

Mass airflow sensor (oem Bosch)
Plugs
Wires (bougicord)
Cap and rotor (oem Bosch)
Vacuum lines are all new
PCV replaced 5000 miles ago

Only thing I can think of next is the idle air control valve. Those things are not cheap either. Is there a proper way to test them? I cleaned mine about this time last year.

Power band is still strong. I have no codes.

I offer my supplications to my Volvo brain trust. :D
Two things I have done to fix this problem on my T5 after doing the above, as others have said, clean the ECT pins, and replace the fuel pump relay.


'98 S70 T5M - 270,000+mi - forever a project
'99 S70 "AWD" - 218,000+mi - project
Knows enough to be dangerous :wink:

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