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Rough start every few starts but runs fine cold or hot

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TheMrFailz
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TheMrFailz

Rough start every few starts but runs fine cold or hot

Post by TheMrFailz » Tue Oct 23, 2018 8:13 pm

Every once in a while when I go to start my car up (hot or cold, but tends to happen more often when cold) it'll take a few seconds longer than usual (from <3 sec normally to about 5 max during rough starts) to start and i'll get a misfire here or there but then it'll immediately jump to life and be right as rain. I'm a bit worried about it as today when I started it again after just coming back from a trip out to town it started starting rough, made a clunk like it seized, and half a second later went back to rough starting before springing to life as usual. I'm not really sure what it could be as AFAIK everything other than startup is perfectly fine.

Info:
- Car: 2002 v70 2.4t, ~185k miles.
- Oil: 5w-30 Synthetic, usually running regular old generic Mobil 1. I do roughly a 5k mile interval. I am coming up on an oil change.
- PCV was completely functional as of 6 months ago when I last checked crank case pressure. It's night time now but come tomorrow I can run out to the store and grab some rubber gloves to check again.
- Starter motor is the original one.
- Not starting with AC or any notable power draw.
- No noted loss of power.
- Current weather is ranging from 40F to 55F although it was doing that back when it was anywhere from 75-95F.
- No codes after rough start although I think a misfire gets thrown quick (and then cleared) whenever I get said misfire while starting.
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RickHaleParker
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Re: Rough start every few starts but runs fine cold or hot

Post by RickHaleParker » Tue Oct 23, 2018 8:20 pm

Turn the key on, wait 15 seconds then start. See if that makes a difference in how it starts up.
--------
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.
Platform P2 2004 S60R, B2524T4, AW50/51 AWD, Bosch Motronic 7.0, BorgWarner K24 turbocharger, Plant Ghent Belgium.

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TheMrFailz
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TheMrFailz

Re: Rough start every few starts but runs fine cold or hot

Post by TheMrFailz » Wed Oct 24, 2018 8:56 am

Just tested it and it goes a lot better without any misfires.
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RickHaleParker
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RickHaleParker

Re: Rough start every few starts but runs fine cold or hot

Post by RickHaleParker » Wed Oct 24, 2018 3:56 pm

If waiting 15 seconds does the trick, your fuel pressure is bleeding off as the car sits. Waiting 15 seconds gives the fuel pump time to build the pressure back up.
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TheMrFailz
--------
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.
Platform P2 2004 S60R, B2524T4, AW50/51 AWD, Bosch Motronic 7.0, BorgWarner K24 turbocharger, Plant Ghent Belgium.

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TheMrFailz
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TheMrFailz

Re: Rough start every few starts but runs fine cold or hot

Post by TheMrFailz » Wed Oct 24, 2018 4:20 pm

RickHaleParker wrote:
Wed Oct 24, 2018 3:56 pm
If waiting 15 seconds does the trick, your fuel pressure is bleeding off as the car sits. Waiting 15 seconds gives the fuel pump time to build the pressure back up.
By any chance is this at all related to a dirty fuel filter? I ask because I don't have any records of previous owners replacing the one on mine and I'm hitting 184k miles now.
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abscate
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abscate

Re: Rough start every few starts but runs fine cold or hot

Post by abscate » Thu Oct 25, 2018 7:00 am

Get a fuel pressure gauge on the rail and measure it. The fuel pressure has to be up to snuff
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RickHaleParker
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Re: Rough start every few starts but runs fine cold or hot

Post by RickHaleParker » Thu Oct 25, 2018 3:18 pm

If you change the fuel filter it might start up better. The fuel filter is a maintenance item. With a unknown history, I would go ahead and replace it.
--------
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.
Platform P2 2004 S60R, B2524T4, AW50/51 AWD, Bosch Motronic 7.0, BorgWarner K24 turbocharger, Plant Ghent Belgium.

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