Severe misfire/bogging
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This is a discussion on Severe misfire/bogging within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hey guys, just shooting this question out there to see if anyone has had a similar issue, any tips or ...

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    Registered User EvoEatr's Avatar
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    Severe misfire/bogging

    Hey guys, just shooting this question out there to see if anyone has had a similar issue, any tips or information is def. appreciated here...I have a 2002 WRX, Built 2.5 hybrid motor, GT32 Turbo, FMIC, water injection, supporting mods...Whenever I give the car full throttle or close to it, the car bogs out and seems to misfire extremely bad, to the point of raw fuel (black smoke) pouring out the exhaust. I also notice I have to give it all I can to get it past like 4k rpms, I can drive it around all day at low boost levels or just normal driving and it drives perfect up throughout the rev range. I have had these mods with this tune for the better part of 20k miles and never had an issue like this...The first thing that came to my mind was spark plugs, I have one step colder plugs in there and they have been in there a few years and prob. more than 20k miles ( at least 4 or 5 dozen WOT tuning pulls )....I have checked extensively for boost leaks and there dont seem to be any, ( t-bolt clamps on all intake piping)... The CEL is not on however I am going to see if any codes are present tomarrow, as well as pull at least one plug to see the condition. Also I just installed a larger water injection nozzle, however I did one pull with it on and it did it, than I did a pull with the water injection off and it did it also so I highly doubt thats the problem...ANY advice here on things to check or any similar stories I would love to hear it...Thanks in advance for all your time...

    OH its a 5spd trans.

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    Good news, everyone! xxxxxxxAnub1s's Avatar
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    Do you have any way to datalog by chance?
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    Registered User EvoEatr's Avatar
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    Quote Originally Posted by Anub1s View Post
    Do you have any way to datalog by chance?

    That was my second thought actually, I do datalog however Im in the process of trying to recover my "modified" ecu definitions from my old laptop, I am kind of hoping some kind of code was thrown so I can at least look at some freeze frame...

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    Good news, everyone! xxxxxxxAnub1s's Avatar
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    Quote Originally Posted by EvoEatr View Post
    That was my second thought actually, I do datalog however Im in the process of trying to recover my "modified" ecu definitions from my old laptop, I am kind of hoping some kind of code was thrown so I can at least look at some freeze frame...
    Ah, gotcha. Well if you are stumped with the logs on what the issue could be, post them up and let us have a look. I'll try my best to help but I know that Ron or others could help if I can't.
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    Registered User EvoEatr's Avatar
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    Quote Originally Posted by Anub1s View Post
    Ah, gotcha. Well if you are stumped with the logs on what the issue could be, post them up and let us have a look. I'll try my best to help but I know that Ron or others could help if I can't.

    Thanks man, appreciate it......I'm hoping its the plugs or even a coil, something somewhat inexpensive and easy haha..

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    Registered User EvoEatr's Avatar
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    Ok, took her into work today and pulled the cyl #1 plug out, after scanning to make sure there where no codes, the spark plug looked pretty bad, white and a tad ashy, looks like I will be replacing the plugs and seeing what we have, For some odd reason I called 5 different auto parts stores and also checked the parts dept at work and no one had them in stock, NGK Iridium, amazing haha

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    Registered User EvoEatr's Avatar
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    Ok, I have read extensively on how to choose spark plugs/ heat ranges etc etc etc...I am soley looking for peoples opinions/ stories here....The stock NGK's in my WRX are a heat range of 6, When I pulled my plug out the other day it has a heat range of 9...thats three steps colder, I have read and read on this and apparently the most relevant thing I can seem to find is that a rule of thumb is for every 75-100 HP gain in engine power you should go a step colder ( yes I do realize there are also other factors involved)...My best bet at this point is my motor is making close to 600 HP, thats quite a step up from the stock 227 HP. so if you go by this logic than three steps colder doesnt seem to farfetched... Anyone have any input on this topic?

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    The Fruit mangostick's Avatar
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    A spark plug thats white and ashy is usually sign of running lean brother.. Thatsanogood.. have you checked your fuel pressure at wot? how do the rest of the plugs look? I'm wondering if your fuel pump is fading at higher demand levels.

    Since you're running water injection though.. Its also possible the white ashy stuff is deposit burning off in the combustion process.. which will eventually weaken the spark (enough to cause top end misfire or misfire under boost over time). Can you get us a good close pic of the plugs? That will help out a lot.

    Another thought.. if they're that much cooler than the factory plug.. could cause fouling because they aren't in the right heat range.... I've run into this on other force fed engines, I imagine its not impossible with the boxer config.

    Check fuel pressure under load, change the plugs for the correct heat range.. and get us pics of old plugs!
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    Quote Originally Posted by mangostick View Post
    A spark plug thats white and ashy is usually sign of running lean brother.. Thatsanogood.. have you checked your fuel pressure at wot? how do the rest of the plugs look? I'm wondering if your fuel pump is fading at higher demand levels.

    Since you're running water injection though.. Its also possible the white ashy stuff is deposit burning off in the combustion process.. which will eventually weaken the spark (enough to cause top end misfire or misfire under boost over time). Can you get us a good close pic of the plugs? That will help out a lot.

    Another thought.. if they're that much cooler than the factory plug.. could cause fouling because they aren't in the right heat range.... I've run into this on other force fed engines, I imagine its not impossible with the boxer config.

    Check fuel pressure under load, change the plugs for the correct heat range.. and get us pics of old plugs!
    Alright man thanks, I do have an inline fuel psi gauge under the hood, the entire fuel system is redone so Idk im kind of finding it hard to believe I have a fuel psi issue, my first thought as soon as it happened was the plugs, I'm thinking of stepping back one heat range so I would only be two colder than stock...Any opinion here? When I pull the plugs out again I will be sure to get a decent pic... Actually let me ask you another question, Whats the fuel pressure regulator good up until, I mean I do know what it does and how it works, I'm just curious as to what level is the stock unit good until? I have modded stock 800cc injectors, Aeromotive fuel rails, large fuel lines on top of the manifold, fuel pressure gauge, and an in tank Walbro 255...all with the stock fuel pressure regulator..Thanks for all the info. man...

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    Moderator Donkey's Avatar
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    The stock regualtor generally works fine up to around 30 psi boost I believe. There is no conrete numbers,just going by what people are running out there. The stock FPR is a rising rate of 1:1 so for every 1psi of boost the fuel pressure rises 1 psi to counteract the manifold pressure against the injector nozzle. I would maybe look at a bad coil pack or fuel pump. Have you cleaned the MAF recently?
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    Quote Originally Posted by Donkey View Post
    The stock regualtor generally works fine up to around 30 psi boost I believe. There is no conrete numbers,just going by what people are running out there. The stock FPR is a rising rate of 1:1 so for every 1psi of boost the fuel pressure rises 1 psi to counteract the manifold pressure against the injector nozzle. I would maybe look at a bad coil pack or fuel pump. Have you cleaned the MAF recently?

    Yea, I was kind of thinking that, I dont think I have ever seen a problem with a Subaru FPR even on modded WRX's, just a thought ...I have some time off on Thursday and I will be changing the plugs, changing the air filter, cleaning the MAF, and taking a peek at fuel pressure, Thanks for the tips man...

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    The Fruit mangostick's Avatar
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    agree'd on all points.. I've had a walbro hp255lph fail on me before.. granted in a ford application but a fuel pump is a fuel pump. It is possible. Mine failed in a odd way too, there's a brass retainer on top of the outlet nipple that holds the pressure nozzle in place. Mine had come off and wedged in the fuel line. Car fell flat on its face but ran fine from 3500rpm on down. Idled great. Finally had to tape a fuel pressure gauge to the windshield so I could keep a eye on it when into boost.

    While this may not be your issue.. it never hurts to check.

    I'm with you on the plugs and heat range. Too cool will allow deposits to form. Turbo cars are notoriously picky about plugs.. very well could fix the issue with a good set of new plugs.
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    Quote Originally Posted by mangostick View Post
    agree'd on all points.. I've had a walbro hp255lph fail on me before.. granted in a ford application but a fuel pump is a fuel pump. It is possible. Mine failed in a odd way too, there's a brass retainer on top of the outlet nipple that holds the pressure nozzle in place. Mine had come off and wedged in the fuel line. Car fell flat on its face but ran fine from 3500rpm on down. Idled great. Finally had to tape a fuel pressure gauge to the windshield so I could keep a eye on it when into boost.

    While this may not be your issue.. it never hurts to check.

    I'm with you on the plugs and heat range. Too cool will allow deposits to form. Turbo cars are notoriously picky about plugs.. very well could fix the issue with a good set of new plugs.

    Thanks man, I have no problem whatsoever understanding cars in general however the high performance world can sometimes be tricky , appreciate all the tips and input

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    The Fruit mangostick's Avatar
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    Quote Originally Posted by EvoEatr View Post
    Thanks man, I have no problem whatsoever understanding cars in general however the high performance world can sometimes be tricky , appreciate all the tips and input
    No worries, you're barkin up the right tree Sometimes helps to hear it from other people to put the worry to rest though. btdt.. many many times.
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    Registered User EvoEatr's Avatar
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    So I replaced the plugs today at work, also pulled the front bumper and replaced the air filter and cleaned the MAF, the MAF had a oil on it, I also installed my new stainless steel brake lines and rotated the tires, anyways I have yet been able to duplicate my problem, my bet is that it was a combo of the almost completely clogged air filter and a dirty, oily MAF...All good Thanks for the tips guys

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