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06-25-2022, 12:59 PM | #1 |
Scooby Specialist
Member#: 306422
Join Date: Jan 2012
Location: Syracuse
Vehicle:2005 Impreza 2.5RS Dark Blue |
Bucking / Misfire / Hesitation under WOT boost - Thoughts?
Hey guys I just wanted to throw this thread out there to get some input on what you guys might suggest may be going on with my 02 WRX. Car was off the road for 6 years and I just got back on the road again. Ive been driving it for about 3 weeks with no issues at first.
Slowly a hesitation issue has been building this past week and has gotten to its worse point last night Im getting a serious stumble or misfire when entering boost under WOT. No codes, no flashing CEL, I spent some time trying to isolate the condition and this is what I can report: It is most violent when cruising at highway speed in 5th .. say 60mph .. and then downshifting to 3rd (passing a car for example). If I downshift aggressively and go WOT the car bucks violently ( exhaust sounds similar to hitting limiter) until I pull my foot off the gas a little ... say 75% throttle ... then everything cleans up and I can go 100% throttle and it enters boost strong all the way to redline If I do the same scenario but only drop to 4th, there is a very slight hesitation as it enters boost but then cleans up on its own and boosts strong until redline Same scenario, but leave it in 5th and go WOT it slowly enters boost with no noticeable issues. Last scenario: WOT pull from a dig. 1st pulls strong all the way to redline. 2nd seems normal and strong all the way to redline, 3rd there is a slight stumble, but it clears up without back out of the throttle all the way to redline, 4th same hesitation entering boost the clears up on its own and boosts strong to redline. After doing some research Im going to start my cleaning the MAF first, as it is a next to $0 cost to try If that doesn't work Ill try new plugs (current are 8 years old with only maybe 3k on them) Then maybe try coil packs, current are the OEM originals Just wanted to see if anything specific jumps out to you guys based on the scenarios above, any input is greatly appreciated. E-Tuned to 20PSI Invidia N1 3" CBE Powers Enterprise PE1818 Turbo Grimmspeed Catted 3" Downpipe (Divorced WG) Grimmspeed EBCS Tomei Uppipe Tomei Unequal Length Header Perrin Turbo Inlet Modified Injen CAI HyperFlow FMIC STI Pink Injectors Walboro 255LPH Fuel Pump GFB Mach 2 TMS BPV GFB Underdrive Pulley Kit --Lightweight Crank Pulley --Lightweight PS Pulley --Lightweight Alt Pulley
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06-25-2022, 01:21 PM | #2 |
Scooby Guru
Member#: 67004
Join Date: Jul 2004
Chapter/Region:
SCIC
Location: (818) 300k+ ej205 ppg 5mt
Vehicle:02 vf30 pnp wagon silver and cf |
Most of the time when you have the WOT and spitting is a A/F issue. Common thing would be to check the plugs. Then look at any leaks vacuum and turbo inlet. Also you have to consider the tune and where it got tuned. Say if you moved several states away and had an elevation change and such. There are many threads on misfire issues from wiring to coilpacks. Yet WOT is generally a A/F issue, generally 3/4 to WOT. If it was me I'd look at some new NGK and gap them more toward the minimum to give a stronger spark, like 0.028 gap.
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06-25-2022, 01:30 PM | #3 | |
Scooby Specialist
Member#: 306422
Join Date: Jan 2012
Location: Syracuse
Vehicle:2005 Impreza 2.5RS Dark Blue |
Quote:
Only thing that makes be scratch my head is why the car was driving great for a while and then developed the miss. I would think that if it were a poorly gapped plug it would have been present when I first put it back on the road |
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06-25-2022, 01:57 PM | #4 |
Scooby Newbie
Member#: 379520
Join Date: Jan 2014
Location: El Paso Texas
Vehicle:2005 Wrx WRB |
I’ve had some similar issues with my 05 wrx. Make sure all your grounds are clean and secure. Could add a couple of extra grounds. Since it’s at wot probably won’t be this but the idle air control valve can be cleaned also make sure to get a new gasket if you open it up. Check your oil level. My car was acting up one time because I was low on oil.
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06-25-2022, 04:03 PM | #5 | |
Scooby Specialist
Member#: 306422
Join Date: Jan 2012
Location: Syracuse
Vehicle:2005 Impreza 2.5RS Dark Blue |
Quote:
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06-25-2022, 07:36 PM | #6 |
Scooby Guru
Member#: 67004
Join Date: Jul 2004
Chapter/Region:
SCIC
Location: (818) 300k+ ej205 ppg 5mt
Vehicle:02 vf30 pnp wagon silver and cf |
Common misconception that the gap is good out of the box. Auto parts stores love to say that but for suby's they are a bit more needing to have the plug gap on point to maintain the correct a/f. Maf is always a good place to start, yet if you have a leak after the maf it will cause issues with not having the correct a/f, depending on how big the leak is. I've found leaks at the throttle body gasket, turbo inlet, y pipe gaskets on the tmic, and the bov gasket. But most of the time with bucking I found it was related to plug gap, unless it was tune related. On gaskets that I wasn't going to re-vist often I would silicone them, like the y pipe. Hopefully you get it solved GL
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06-30-2022, 02:18 PM | #7 |
Scooby Specialist
Member#: 333468
Join Date: Sep 2012
Chapter/Region:
RMIC
Location: SLC, UT
Vehicle:93 SS - 06 OB XT 03 WRB GD 205/22T 20G-XT |
Lots of threads with this same issue. I've run into it multiple times as well.
What fixed mine after exhausting all other possibilities was replacing all the coil packs. If your car is old then new coilpacks is a good idea anyway. NGK coilpacks from RockAuto aren't that expensive and as good as OEM. Don't cheap out on these. Here is my list of things to check: Check all your grounds and battery terminal connections. Add grounds. Change plugs and check gaps, make sure plugs aren't loose. Boost Leak test. Check vacuum lines. Check fuel pump and fuel pump sock. Change fuel filter. Could be bad fuel pressure regulator. Replace MAF. Replace BCS. Replace alternator. Replace coil packs. Replace coil pack connectors. Tackle the easiest things first. |
06-30-2022, 02:36 PM | #8 |
Scooby Specialist
Member#: 515308
Join Date: Jun 2020
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Mine was coil packs, the 2020 black sti coils are same as gray, same dwell map, but u can get pull offs with 10k miles cheap
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07-04-2022, 08:47 AM | #9 |
Scooby Specialist
Member#: 306422
Join Date: Jan 2012
Location: Syracuse
Vehicle:2005 Impreza 2.5RS Dark Blue |
Thanks guys.
This happened right before I went on vacation for a week. Im back now and will start trying some things in the next couple days. Ill post what worked and what didnt. |
08-30-2022, 09:47 AM | #10 | |
Scooby Newbie
Member#: 531232
Join Date: Aug 2022
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Quote:
I realize this post is about 6 weeks old.. I'm trying to troubleshoot an 04 WRX that appears to have a fuel related issue. (And I need to reply to a few posts before I can create a post of my own...). |
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08-30-2022, 11:19 AM | #11 |
Scooby Specialist
Member#: 125887
Join Date: Sep 2006
Chapter/Region:
NWIC
Location: Southern Oregon
Vehicle:2001 EJ207 V7 RSTi, Mica Blue |
That old of vehicle, I would point to coil packs of all other bases have been covered
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08-30-2022, 03:24 PM | #12 | |
Scooby Specialist
Member#: 306422
Join Date: Jan 2012
Location: Syracuse
Vehicle:2005 Impreza 2.5RS Dark Blue |
Quote:
I have new plugs to go in this weekend to see if that changes anything |
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09-06-2022, 06:57 PM | #13 |
Scooby Specialist
Member#: 333468
Join Date: Sep 2012
Chapter/Region:
RMIC
Location: SLC, UT
Vehicle:93 SS - 06 OB XT 03 WRB GD 205/22T 20G-XT |
At this point I would get a new MAF. They stop working 100% as they get old. Find the Denso part number and you can order one on Amazon for a lot less than the dealer.
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09-07-2022, 02:50 PM | #14 |
Scooby Specialist
Member#: 306422
Join Date: Jan 2012
Location: Syracuse
Vehicle:2005 Impreza 2.5RS Dark Blue |
The MAF is only about 6 years old. I replaced it before I initially had the car tuned. Probably less than 10k miles on it.
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09-07-2022, 04:22 PM | #15 | |
Scooby Specialist
Member#: 333468
Join Date: Sep 2012
Chapter/Region:
RMIC
Location: SLC, UT
Vehicle:93 SS - 06 OB XT 03 WRB GD 205/22T 20G-XT |
Quote:
Have you checked this thread out? - https://forums.nasioc.com/forums/sho....php?t=2403736 |
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09-09-2022, 03:21 PM | #16 | |
Scooby Specialist
Member#: 306422
Join Date: Jan 2012
Location: Syracuse
Vehicle:2005 Impreza 2.5RS Dark Blue |
Quote:
I did have to extend the wiring harness for the MAF. I remember the first time, I did not properly connect the shielding back together and had to redo it. Wonder if it may be a gremlin from that. Ill add it to the list. Unfortunately Ive been so short on time lately that I may not get this diagnosed before I have to put it up for the winter lol |
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09-18-2022, 07:22 PM | #17 |
Scooby Specialist
Member#: 306422
Join Date: Jan 2012
Location: Syracuse
Vehicle:2005 Impreza 2.5RS Dark Blue |
Got the fresh plus in today...
Could have sworn I went with 1 step colder NGK iridums But the part numbers showed they were 1 step colder coppers, and were gapped to a pretty loose .030 Two of the new iridiums were a perfect .028 and two had to be gapped down from a tight .030 to .028. I cant feel any more sign of hesitation of missing during boost which is great. But there is still this feeling like the car is struggling to build boost mid rev range in 3rd gear. Ill do a boost leak test next just to make sure. Also something frustrating I noticed ... my tune is set for a peak boost of 20psi. My AEM boost gauge shows that I am hitting target boost, but when its showing 20 psi on my gauge, the Accessport is only showing 16-17psi?? |
09-18-2022, 07:22 PM | #18 |
Scooby Specialist
Member#: 306422
Join Date: Jan 2012
Location: Syracuse
Vehicle:2005 Impreza 2.5RS Dark Blue |
Got the fresh plugs in today...
Could have sworn I went with 1 step colder NGK iridums before But the part numbers showed they were 1 step colder coppers, and were gapped to a pretty loose .030 Two of the new iridiums were a perfect .028 and two had to be gapped down from a tight .030 to .028. I cant feel any more sign of hesitation or missing during boost which is great. But there is still this feeling like the car is struggling to build boost mid rev range in 3rd gear. Ill do a boost leak test next just to make sure. Also something frustrating I noticed ... my tune is set for a peak boost of 20psi. My AEM boost gauge shows that I am hitting target boost, but when its showing 20 psi on my gauge, the Accessport is only showing 16-17psi?? |
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