Baka.sti Posted February 3, 2021 Share Posted February 3, 2021 Hello everyone I was wondering if I could have a helping hand so here is the story I was driving my Sti was waiting at a red light when the light turned green I accelerated once I reached about 20 mph the car seemed like it wasn’t giving me power and seemed like it was bogging and when trying to accelerate or go past around 20 mph it shut off completely I pulled over and my check engine came on I read it with a scanner and it said p0304 which is a misfire in cylinder 4 so would it be best to change the spark plugs first? Quote Link to comment Share on other sites More sharing options...
heartless Posted February 3, 2021 Share Posted February 3, 2021 not necessarily you can certainly pull the plug and check its condition, but misfires are more commonly caused by either plug wire or coil problems, sometimes by fouled plugs - you need to do a bit of investigation to learn more about what is causing the misfire. Quote Link to comment Share on other sites More sharing options...
Baka.sti Posted February 3, 2021 Author Share Posted February 3, 2021 Thank you I appreciate it I will check the plugs tomorrow and I might be concerned or I honestly don’t know if this information is useful but before the check engine came on I would sometimes get a strong exhaust smell or I would get a rough idle but the car would then idle normally and would only happen probably once a week. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted February 3, 2021 Share Posted February 3, 2021 more info on car please. kinda seems like it may have gone into 'limp' mode. maybe you've had a valve sticking or ???? proceed carefully and check everything including timing. Quote Link to comment Share on other sites More sharing options...
heartless Posted February 3, 2021 Share Posted February 3, 2021 Agree with 1LT - we need more info on the car, and as much background info as possible need year, specific model, mileage, etc... any modifications to the car? how long have you had it? side note.. please update your profile with just city & state - not the street address. Quote Link to comment Share on other sites More sharing options...
Baka.sti Posted February 4, 2021 Author Share Posted February 4, 2021 Hey guys I haven’t pulled the plugs yet but yes my car did go into limp mode and shut off but then turned on but would try and turn off but barley sputtered to stay on Quote Link to comment Share on other sites More sharing options...
Baka.sti Posted February 4, 2021 Author Share Posted February 4, 2021 My car is a 2011 Subaru Sti hatchback the only mods are a Cobb intake and a straight pipe both from previous owner I barley got the car a month ago from a dealer Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted February 4, 2021 Share Posted February 4, 2021 (edited) clear the ECU, try to start, scan for codes. How old are the plugs? are they NGK appropriate for the car? inspect the cyl4 plug for sure. Look for signs of oil in the plug's tube/on the boot/plug. you could swap cyl 4 coil for cyl 2 to test coil, etc. If you need a mechanic, in a new thread, ask for recommendation of a soob-friendly shop near your city. Edited February 4, 2021 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
Baka.sti Posted February 4, 2021 Author Share Posted February 4, 2021 Sounds good I’m actually going to swap out all plugs on Monday and check them all and I’m not sure what plugs are in right now or how old I bought this car from the dealer last month they said they had done a service on it and a check in the engine but I’ll check the plugs Monday I appreciate all your guy’s help Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 4, 2021 Share Posted February 4, 2021 (edited) If it has a COBB intake it MUST be tuned for it. Does it have a COBB Access Port? Make sure it has the correct map loaded for the COBB SF intake. The fact that it now has a cylinder 4 misfire, and has at times ran rough, AND the car came from a used car lot...... it's very possible that it does not have a proper map loaded or possibly hasn't been tuned at all for the intake if someone unmarried the AP and traded the car in..... without the map for that intake loaded the car will run very lean and with a lot more timing than it should have. Cylinder 4 is often the first cylinder to break a ring land in those circumstances and it's quite possible that you will need to install some new Forged Pistons, get an Access Port, and a PROPER dyno tune. Expect that to cost around $5,000-6,000. It is highly unlikely to be a spark plug. They come with laser Iridium plugs and they really don't fail. GD Edited February 4, 2021 by GeneralDisorder 1 Quote Link to comment Share on other sites More sharing options...
Numbchux Posted February 4, 2021 Share Posted February 4, 2021 The factory service manual has a several page diagnostic chart for P030x codes. Tune-up is definitely the place to start, but it could be any one of about a dozen things. Ranging from a loose hose to a blown engine and everything in between. Quote Link to comment Share on other sites More sharing options...
Baka.sti Posted February 4, 2021 Author Share Posted February 4, 2021 The car never felt out of power or would ever go into limp mode before this and it would idle rough for only a couple seconds then jump back into rhythm I have warranty on the car but I have oil in the car I checked all fluids there’s isn’t anything leaking they were all filled so I’m hoping it’s just the spark plug but when they arrive on Monday I’ll know for sure if it was just the spark plug or see the real problem I honestly don’t know if it had an accessory before but I’m planing to get one after a AOS Quote Link to comment Share on other sites More sharing options...
Baka.sti Posted February 4, 2021 Author Share Posted February 4, 2021 Access port *** Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 4, 2021 Share Posted February 4, 2021 You don't need an AOS. Worst idea ever. Get an Access Port and a proper tune. That vehicle CANNOT BE DRIVEN SAFELY without a tune using the COBB SF Intake. Is that clear enough? GD Quote Link to comment Share on other sites More sharing options...
Baka.sti Posted February 4, 2021 Author Share Posted February 4, 2021 Yes sounds good but isn’t the AOS necessary since it helps prevent ring land failure but I will buy the access port first Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 5, 2021 Share Posted February 5, 2021 (edited) 3 hours ago, Baka.sti said: Yes sounds good but isn’t the AOS necessary since it helps prevent ring land failure but I will buy the access port first The AOS does nothing useful. It doesn't prevent anything. Don't believe everything you read on the internet. Are you burning oil? If you are then your engine or turbo is blown. An AOS isn't going to help it is just a band-aid for a blown or poorly built engine. On cars that don't have excessive oil consumption the AOS is really an "Air Liquid Separator" and just captures a bunch of condensation which mixes with crankcase gasses and turns into a thick white milkshake like substance that coats the inside of all the breather hoses, and AOS or catch can, etc since the engine cannot burn off the acidic gasses and condensation from cold starts. This just fouls everything. The Subaru crankcase design already incorporates an AOS - it's built directly into the back of the engine block casting and is covered on the back side by the Separator Plate (see the irony?) this box inside the engine block is safely located where it will be heated by engine block heat and thus will not create problems with condensation. If Subaru thought it would be a good idea to put that component external to the block they would have done so. Same goes for the "cylinder 4 cooling mod". If the hundreds of engineers that spent thousands of hours designing and testing the EJ platform for the last 40+ years had found this $5 fitting and hose package would make a measurable difference in combustion chamber temps then it would have been included in the factory design architecture. The reality is that *even if* (and it's arguable) it resulted in 3 or 5 degrees of difference in the coolant jacket temperature - this would make no measurable difference to the 2000 degree combustion temps when the engine is at WOT full boost. 3 degrees in the cooling jacket, if that were to translate 100% into combustion temps (it doesn't) would be a change of 0.15% - likely not measurable and definitely not going to make any difference in detonation or piston longevity. PROPER TUNING is what prevents pistons from breaking. And that's hard to come by. Our tuner has 18 years of Subaru tuning experience and has the 3rd COBB Pro license ever issued back in 2003. He was one of their beta testers for the AP version 1 and COBB offered to buy his maps for inclusion on the AP (off the shelf maps). He drew the line at that and to this day his maps are only available through him at my shop. GD Edited February 5, 2021 by GeneralDisorder Quote Link to comment Share on other sites More sharing options...
Baka.sti Posted February 5, 2021 Author Share Posted February 5, 2021 Honestly this is why I appreciate people like you because honestly I was going to buy an AOS just because of what people say on YouTube and how it helps the engine but I’m glad there are people like you that are knowledgeable with Subaru and their engines where is your shop located if you don’t mind me asking and the next thing I will get will be the Cobb access port and I appreciate you guys a lot for all the input and help/knowledge Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted February 5, 2021 Share Posted February 5, 2021 I learn so much from GD. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 5, 2021 Share Posted February 5, 2021 12 hours ago, Baka.sti said: Honestly this is why I appreciate people like you because honestly I was going to buy an AOS just because of what people say on YouTube and how it helps the engine but I’m glad there are people like you that are knowledgeable with Subaru and their engines where is your shop located if you don’t mind me asking and the next thing I will get will be the Cobb access port and I appreciate you guys a lot for all the input and help/knowledge We are located in Portland, OR. Yes you need an AP to apply a safe tune for the SF intake. In the meantime it's only safe to drive if you STAY COMPLETELY OUT of boost. Drive it like there's an egg between your foot and the accelerator pedal. If you have a scan tool check the fuel trims. GD Quote Link to comment Share on other sites More sharing options...
Mike104 Posted February 5, 2021 Share Posted February 5, 2021 My oldest child (totally useless with technical things) was going to relocate to Portland and I was hopeful that they would at least be able to get car work done at your shop. Alas it's now Seattle. As I will be across the country I will no longer be in a position to help when car issues arise. Hopefully AAA will be able to get the car to you Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 5, 2021 Share Posted February 5, 2021 If it's any kind of large job, it's usually cheaper to tow it to me than to pay the higher rates plus sales tax in Seattle. No sales tax down here so that can be a significant advantage. I have a lot of customers north of the border. GD Quote Link to comment Share on other sites More sharing options...
lmdew Posted February 6, 2021 Share Posted February 6, 2021 1+ on GD's shop. I told Friends in Bellingham, WA well north of Seattle to head down! Quote Link to comment Share on other sites More sharing options...
Baka.sti Posted February 6, 2021 Author Share Posted February 6, 2021 Okay sounds good well I’m going to pull the plugs tomorrow they came in early so I will see if it is just the plug and if not I will asses from there but next to get is definitely the AP thanks GD I appreciate you and also would the AP also be beneficial since I’m pretty sure the previous owner removed or gutted the cat pipe so it’s loud or would I have to get a proper tune Quote Link to comment Share on other sites More sharing options...
heartless Posted February 6, 2021 Share Posted February 6, 2021 21 hours ago, GeneralDisorder said: We are located in Portland, OR. Yes you need an AP to apply a safe tune for the SF intake. In the meantime it's only safe to drive if you STAY COMPLETELY OUT of boost. Drive it like there's an egg between your foot and the accelerator pedal. If you have a scan tool check the fuel trims. GD 8 hours ago, Baka.sti said: Okay sounds good well I’m going to pull the plugs tomorrow they came in early so I will see if it is just the plug and if not I will asses from there but next to get is definitely the AP thanks GD I appreciate you and also would the AP also be beneficial since I’m pretty sure the previous owner removed or gutted the cat pipe so it’s loud or would I have to get a proper tune umm, seems to me that question has already been answered.. just getting the AP is not enough, you need to have it properly tuned as well. Perhaps you should reread GD's FIRST reply to you about this - lots of good info in it. On 2/4/2021 at 1:16 PM, GeneralDisorder said: If it has a COBB intake it MUST be tuned for it. Does it have a COBB Access Port? Make sure it has the correct map loaded for the COBB SF intake. The fact that it now has a cylinder 4 misfire, and has at times ran rough, AND the car came from a used car lot...... it's very possible that it does not have a proper map loaded or possibly hasn't been tuned at all for the intake if someone unmarried the AP and traded the car in..... without the map for that intake loaded the car will run very lean and with a lot more timing than it should have. Cylinder 4 is often the first cylinder to break a ring land in those circumstances and it's quite possible that you will need to install some new Forged Pistons, get an Access Port, and a PROPER dyno tune. Expect that to cost around $5,000-6,000. It is highly unlikely to be a spark plug. They come with laser Iridium plugs and they really don't fail. GD Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 6, 2021 Share Posted February 6, 2021 (edited) 10 hours ago, Baka.sti said: Okay sounds good well I’m going to pull the plugs tomorrow they came in early so I will see if it is just the plug and if not I will asses from there but next to get is definitely the AP thanks GD I appreciate you and also would the AP also be beneficial since I’m pretty sure the previous owner removed or gutted the cat pipe so it’s loud or would I have to get a proper tune The AP comes with maps that are already setup for the COBB SF intake. They also come with a map for the SF intake and the COBB downpipe. Those maps are pre-loaded on the AP and can be used as soon as you install it without custom tuning. They DO NOT have a map to delete the converter entirely - the COBB downpipe has a high-flow converter, as do most other good name brand downpipes. Other companies do sell downpipes without the converter (usually sold as a "test pipe" or off-road only pipe) but no shop will install them since it's a $10,000 fine if you get caught doing that. There is also basically ZERO benefit to removing the converter. The high flow converters included on performance downpipes are not restrictive. GD Edited February 6, 2021 by GeneralDisorder Quote Link to comment Share on other sites More sharing options...
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