Rough start every few starts but runs fine cold or hot

TheMrFailz · Post by **TheMrFailz** » 23 Oct 2018, 20:13

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.

Post by **RickHaleParker** » 23 Oct 2018, 20:20

Turn the key on, wait 15 seconds then start. See if that makes a difference in how it starts up.

TheMrFailz · Post by **TheMrFailz** » 24 Oct 2018, 08:56

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

Post by **RickHaleParker** » 24 Oct 2018, 15:56

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.

TheMrFailz · Post by **TheMrFailz** » 24 Oct 2018, 16:20

RickHaleParker wrote: ↑24 Oct 2018, 15:56 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.

Post by **abscate** » 25 Oct 2018, 07:00

Get a fuel pressure gauge on the rail and measure it. The fuel pressure has to be up to snuff

Post by **RickHaleParker** » 25 Oct 2018, 15:18

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.