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2004 Forester XT 5 speed
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17 Posts
Discussion Starter · #1 ·
Hi all, noob to the forum and Subarus here. I recently purchased a used 2004 Forester XT from craigslist. It ran great for the most part only having to bring it to a shop for some simple repairs. I recently picked up a new Cobb AP v3 and the SF Airbox/Filter assembly. I installed the stage 1 93 oct. and filter 2 days ago and they seemed to work fine on my way to get gas. Turns out that my local gas stations don't carry 93 oct. I filled up with 91 but I didn't change the map. It drove home fine and I changed the map. The next morning on my way to school I was accelerating fairly aggressive, but not WOT, and the car started to jerk back and fourth. I initially thought it was just me not letting off the clutch smoothly so I kept on. It happened again in the next gear so I pulled over the next chance I got. The car idled horrible and my AP said it had p0303, pfffff, and pffffe codes. I turned the car off but it didn't help. I then crawled to school and worried about it ALL DAY!

The problem was still there and I had to drive home. I noticed that it only started to jerk around 3500 rpm and it idles horribly. I got home and started to research the problem. I tried cleaning the MAF and tightening the SF but to no avail.

I have already emailed Cobb and I'm waiting for a response. I just hope its only a coil or spark plug and my engine didn't detonate. I am low on car funds now because I picked up the AP and SF. I would be very upset if it turns out to be a major problem. If any of you could help it would be greatly appreciated.

:shake: :shrug:
 

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2014 Forester xt prem Cvt
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161 Posts
Put the stock parts back on and retune to stock(uninstall)AP. If it goes away, it either your intake issue or you tuned it wrong. Last I remember, your supposed to real time flash over your base, not reflash the base tune. I'm leaning toward the intake issue. And remember your car needs time to relearn corrections and timing after a flash. Like 20 miles of various driving should get your dam to max
 

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2004 Forester XT 5 speed
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17 Posts
Discussion Starter · #4 ·
Put the stock parts back on and retune to stock(uninstall)AP. If it goes away, it either your intake issue or you tuned it wrong. Last I remember, your supposed to real time flash over your base, not reflash the base tune. I'm leaning toward the intake issue. And remember your car needs time to relearn corrections and timing after a flash. Like 20 miles of various driving should get your dam to max
Thanks I've already uninstalled the AP completely and I'll try to uninstall the SF sometime this weekend. While I have that out I will also swap the coils and check injectors. Anything else I could do while that is off?
 

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Premium Member
2017 VW Golf SportWagen 5MT
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10,784 Posts
Do one thing at a time to keep it simple. Put the stock airbox back on and report back, shorties aren't the best choice for intakes on this car.

If you want, change the oil and look for metal flakes in oil that came out, if something broke internally you'll see it.

Stan
 

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2004 Forester XT 5 speed
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17 Posts
Discussion Starter · #7 ·
I uninstalled the SF and it didnt seem to work at first. I decided to bring it to my local dealer. On the 50 mile journey to the dealer. The car slowly started to get better. By the time I got to town, the car was running like nothing ever happened. The CEL is still on and the cruise is blinking. Should I still bring it in to see if any damage occured?
 

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2004 Forester XT 5 speed
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17 Posts
Discussion Starter · #8 ·
Saturday afternoon I used the uninstalled AP to Reset the ECU. The CEL never came back on and I started to drive home. The car seemed fine until the light blinked for a while and the car seemed to jerk again. I turned myself around and dropped it off at the dealer.

Today they called and said the only thing they could find wrong was a bad rear wiper blade, some interior bulbs that were out, and the airbag light was on. They say that they can not replicate the behavior I was experiencing... I told the woman on the phone that I may have spilled some coolant on the coil... (Forgot to mention it) and she said that could have definitely been the issue.

Anyone else think all this could have resulted from a little coolant?
 

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Smooshed FOTY 2011
2005 Lifted 2.5 XT 5-Speed MT Dual-Range
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5,732 Posts
What "blinked" for a little while????? The Check Engine light?!

If you EVER see the check engine light actually flashing, that is your cue to pull over IMMEDIAETLY and shut off the car. A Flashing CEL means that potential damage is currently occuring to the engine (meaning hard misfires, detonation, etc.)

This is the first thing I would do. Clean the MAF with actual MAF sensor cleaner. Not only the bulb, but there are two VERY fine wires up in the tube of the MAF sensor. DO NOT touch these with the spray nozel, but rather spray the cleaner up there. Let the MAF air dry completely. Reset the ECU using the Cobb Accessport. When you key off the car after resetting the ECU, leave it off for more than 15 seconds, then start it back up. It should crank for a few seconds before starting. If it starts right up, it did NOT reset the ECU correctly.

Drive it around, and see if it continues to throw a code. Again, if the check engine light comes on and flashes, IMMEDIATELY get off the gas, put the car in neutral, pull over and shut it off.

If you keep getting a misfire code on the same cylinder, check the actual injector connector (should be gray) for that cylinder. Mine somehow wiggled itself loose and was just barely connected and was causing my misfire issues. Just check all the connections and check for any broken or loose hoses with the intake system.

You can also "fairly" easily swap coil packs from another cylinder to see if the misfire follows (just to test the $80/each coil packs before just up and replacing them).

If you can't find faults with any of that, I would do a compression check on the cylinder that is thowing the code first, followed by the rest of the cylinders. This is also a good time to check the spark plugs for abnormalities. If all cylinders are all within 7-10% of eachother, you are fine (and I would change the spark plugs and not put the old ones back in), but if you find out you have a compression leak, then you would perform a leak down to find where the compression leak is coming from (valves, rings or gasket). The below videos will show you how to perform said tests if it comes to it. Good luck.


 

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2004 Forester XT 5 speed
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17 Posts
Discussion Starter · #10 ·
What "blinked" for a little while????? The Check Engine light?!

If you EVER see the check engine light actually flashing, that is your cue to pull over IMMEDIAETLY and shut off the car. A Flashing CEL means that potential damage is currently occuring to the engine (meaning hard misfires, detonation, etc.)
Yes, it blinked for a while, sometimes going solid. I cleaned the MAF sensor with QD Sensitive electronic cleaner (read somewhere on this forum its the same as the MAF Cleaner). I uninstalled the Cobb stuff and the car started to return to normal. I drove it to the Subaru Dealer and they are doing a full inspection. I talked to them and they said they didnt find anything wrong, no code or CEL. Do they overlook the inside of the engine? Could they tell if any internal damage occurred? :confused:
 

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2005 Forester 2.5XS 5MT
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143 Posts
They likely won't be able to tell that any actual internal damage occurred without pulling the motor apart and inspecting it. I've not seen any mention of any codes being read. You should get a list of the codes it logged and post them in this thread as well as punching them into the search engine on the forum. That is what the dealer techs will be doing instead of pulling your motor and tearing it down. That should always be your first step when trying to diagnose why a check engine light came on.

Also, did you check to see that the tune you used was compatible with the intake? My understanding (from researching this sort of stuff for my WRX over on NASIOC) is that the Cobb off the shelf tunes support various different intakes, but you have to be sure that the intake you are using is on the list or you run the risk of the tune not being able to get the AFR correct (which can lead to things like the check engine light flashing).
 

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2007 XT Sport 5MT
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24,014 Posts
Your situation sounds like when my cylinder 3 coil pack crapped out. Drove normal until under boost during hard acceleration, then she'd buck and throw the codes you experienced.
Definitely double check everything on cylinder 3. Injector, plug, coil, all connections, and try to rule things out.
Cleaning the MAF was a fix the dealership tried on mine, but it was only temporary.
 

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2004 Forester XT 5 speed
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Discussion Starter · #13 ·
They likely won't be able to tell that any actual internal damage occurred without pulling the motor apart and inspecting it. I've not seen any mention of any codes being read. You should get a list of the codes it logged and post them in this thread as well as punching them into the search engine on the forum. That is what the dealer techs will be doing instead of pulling your motor and tearing it down. That should always be your first step when trying to diagnose why a check engine light came on.

Also, did you check to see that the tune you used was compatible with the intake? My understanding (from researching this sort of stuff for my WRX over on NASIOC) is that the Cobb off the shelf tunes support various different intakes, but you have to be sure that the intake you are using is on the list or you run the risk of the tune not being able to get the AFR correct (which can lead to things like the check engine light flashing).
I have the Cobb Intake and box. The codes that came up on the AP were p0303, pffff, and pfffe. The problem slowly went away after I uninstalled AP, intake, and Reset the ecu, with the CEL only coming on when I hit was under boost.
 
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