Author Topic: Help me diagnose hesitation/misfire! Please :)  (Read 1234 times)

Offline PhamilySedan

  • Elite Member
  • *****
  • Posts: 1349
    • http://www.nebraska-subaru.com
Help me diagnose hesitation/misfire! Please :)
« on: May 07, 2013, 10:48:02 AM »
Alright NSOC'ers I need some help!

I'm having some trouble diagnosing this misfire/hesitation/stumbling or whatever it may be on my 03 WRX. 
Here are the details:
-idle is fine at a steady 500rpm
-cold start is normal
-once the engine starts to get warm, if i start to apply any amount of throttle, car starts to big down/misfire/hesitate.
-from a stop (taking off from 1st gear) with any amount of throttle applied, car struggles to take off due to the hesitation/misfire.
-as I apply throttle from gear 1-2 (or any gear change) car has the same problem with bogging/hesitation.
-it can get up to the speed limit I can maintain but let's say even with 15-25% more throttle will cause the engine to hesitate.

All of this is out of boost of course. I havent let the car go into boost since this has started

I've changed out the fuel pump, and checked spark plugs. 3 of the 4 have a little bit of white residue (powder-like) on the tip and the electrode. The odd ball has no white residue and is black.  Ceramic part of the plug is white, as if it were new.

What could I be looking for next?

Thanks guys!

"Yet another reason I wish I was rich. I would own Crawfords LGT, Block's Gumball, and david's RSTi..."
-Random dude on SoCal Subie

Offline csmiller18

  • Member
  • **
  • Posts: 169
Re: Help me diagnose hesitation/misfire! Please :)
« Reply #1 on: May 07, 2013, 05:29:20 PM »
No CEL?

assuming not, when is the last time the MAF sensor was cleaned?
have you checked fuel pressure? (FPR bad?) I wonder if it drops when the volume needed increases. 

Im really just spit balling and giving you a few ideas. If you want a hand with anything, text me.
« Last Edit: May 07, 2013, 05:32:23 PM by csmiller18 »
2005 WRB STi
2008 YAMAHA R6
2005 HONDA TRX450R

Offline bellevue_xt

  • Member
  • **
  • Posts: 230
  • A STI will call my name someday
Re: Help me diagnose hesitation/misfire! Please :)
« Reply #2 on: June 08, 2013, 07:51:11 PM »
weak coil pack
bad ign wires
maf sensor
egr problems
fuel filter clogged
timing issue

hard to say
92 Loyale wagon 5mt (sold)
96 LGT wagon (sold)
06 OBXT LTD 5mt (sold)
13 Chevy Volt

Offline COswerve

  • Novice
  • *
  • Posts: 15
Re: Help me diagnose hesitation/misfire! Please :)
« Reply #3 on: July 16, 2013, 08:48:36 PM »
Cleaned my CAI filter, and changed the spark plugs made my same problem disapear! Spark plugs are a little pain to change but well worth it

Offline MImpreza

  • Newbie
  • Posts: 7
Re: Help me diagnose hesitation/misfire! Please :)
« Reply #4 on: February 05, 2016, 10:05:24 PM »
It wouldn't hurt to do some logging. If you can find someone with a Tactrix cable you could run some logs. It would be interesting to see what the fuel pressure and MAF voltage is doing during these events. Out of curiosity, which cylinder did that one come out of?

Offline Reverend

  • Elite Member
  • *****
  • Posts: 1634
  • Higgins Blue
    • All We'll Drive
Re: Help me diagnose hesitation/misfire! Please :)
« Reply #5 on: February 06, 2016, 11:06:09 AM »
I would hope he's got it figured out by now!  The thread was created in May of 2013...

Offline MImpreza

  • Newbie
  • Posts: 7
Re: Help me diagnose hesitation/misfire! Please :)
« Reply #6 on: February 07, 2016, 04:38:11 PM »
Fair enough. That's what I get for not reading post dates... Forum is doesn't see a whole lot of action. Still, it's cool there is a Subaru following in this area.

Offline Reverend

  • Elite Member
  • *****
  • Posts: 1634
  • Higgins Blue
    • All We'll Drive
Re: Help me diagnose hesitation/misfire! Please :)
« Reply #7 on: February 08, 2016, 09:18:26 AM »
Yeah, most of the action seems to have migrated to social media.  Our Facebook group is pretty active and there are weekly meets every Wednesday.