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Registered
2004 Forester XT
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29 Posts
Discussion Starter #1
A'hoy

First I want to say thanks for all the insight this place has given me over the years. I'm finally starting to mess with engine modifications and immediately running in to issues. Car is bone stock other than wheels/swift springs.

I just bought a used V2 Accessport for my '04 XT automatic. I updated it with Accessport manager and flashed the latest stage 1 91 octane OTS map from Cobb's site. I am using Washington state 92 octane gas from shell.

I took it out today and it seems to be running fine at low load/RPM but when I gradually bring it to about %75 throttle, the car sputters, loses power. I was watching the feedback knock at this time and it went from a solid 0 to -12 (bad, right?). The car loses almost all power and needs to let that even back out before normal operation. This happened twice before I could get the car home.

I ran a diagnosis on it and it gave me misfire in cylinder 1 and 4 and PFFFE and PFFFF.

I flashed it back to stock and it runs fine at WOT. Plugs are not new but never any issues until now.

Not really sure where to start. Is the tune bringing out an underlying issue? Does the car just need a few miles before it figures itself out? Is there a different tune I should use? Am I safe to flash it back to stage one to datalog or are those knock readings too dangerous?

Any help would be appreciated!
 

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Registered
2007 2.5XT Limited 4EAT
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311 Posts
Hey there, I had a similar issue with my 07 when I first started tuning with my Accessport. I had a stumble right around 3000-3500 RPM along with hitting fuel cut anytime I tried to pass someone. The problem was exacerbated by every increase in either boost or timing. After consulting an E tuner and doing some data logging, the problem turned out to be a lazy boost control solenoid (the stock OEM unit). After swapping out the faulty BCS everything was right as rain. Not sure if this is where to look in your case but, it's somewhere to start. Also, if you haven't already, it would also be a good plan to replace the plugs and coils, MAP sensor and, the O2 sensors. Check for any possible air/vacuum leaks as well. Trying to diagnose a drivability issue without having checked those items off the list is futile.

You will want to consult with a tuner and do some logging. Should be a pretty easy problem to solve with the proper help. Data logging may also help track down some of these issues. There are a few folks here on the forum that can help. While I was trying to sort out my issues a forum member proactively reached out to me and offered to help. Super nice guy and, a Subaru whiz. A few dollars and a handful of emails and everything is right with the world. You can try to send him a PM or, perhaps he will chime in. His forum handle is @MikeDrives1


Good luck!
 

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2004 Forester XT
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29 Posts
Discussion Starter #3
Thanks for the info!

Sounds like this is going to be pretty involved for just stage 1 considering it appears to run just fine stock. Other than the fear of damage, my main concern was whether or not it might just be something the ECU would learn away after 25 miles or whatever.

I'll probably throw it back to stock again and just add plugs/coils to my stage two buying list so I can do them all at once and then dial it in from there. I'd rather not just throw parts at it without being somewhat sure it needs them. The car isn't one of our dailies so I'm trying not to go to crazy spending on it and I have the time to work through it.

Cheers!
 

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Registered
2004 Forester XT
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29 Posts
Discussion Starter #4
Update. Experienced the same loss of power at about 4000 RPM today while using the Cobb stage 0 map so I uninstalled the entire AP and now it is back to running fine.

I suspect a boost issue still but I really don't know. Weighing whether it is worth it to start digging in to it to open that can of worms or if Ishould just keep it stock like we have for the last 150k carefree miles.
 

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2001 Forester STi 6spd with MapDCCD
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4,642 Posts
well, without boring you to sleep on the fine details, more and more its becoming apparent as these sub-08 models age, they seem to experience more reported issues with using strict shelf maps. This has been happening so much so that COBB has now removed a LOT of the downloadable OTS maps for a lot of the sub-2008 models off their site, with the notice posted that you should seek a protune for these years. Im just a PM away if you would like to chat back and forth and do some troubleshooting if you every want to install that AP again.

Also, thank you @Snow3d for the kind words! Always happy to help!
 

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Registered
2004 Forester XT
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29 Posts
Discussion Starter #6
Thanks Mike! I'll keep you in mind if I need some serious help.

I contacted Cobb and a rep reached out to help troubleshoot. I reinstalled the stage 0 map and am sending him some idle logs and going from there. I'll keep this updated if anything comes of it.

I honestly am ok with living without stage 1 and would definitely porotune if I went further so hoping it is an easy fix and I don't have to make that decision soon.

Thanks!
 

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2004 Forester XT
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29 Posts
Discussion Starter #7
OK,

So I contacted Cobb to see what they thought. Super helpful people. They took a look at my car at idle on their stage 0 map and then a couple of half pulls and said everything looked fine. They looked at a log of a power loss event and didn't seem concerned. After about 15 miles on the stage 0 tune, all the hiccups and power loss was gone, even through strong pulls. I never could get the full WOT in third pulls that Cobb wanted (city livin'...) but I figured I'd give stage 1 a try again and stick with it longer.

I flashed it over and it was running poorly. Engine sounds fine (through all of this it sounds just fine) but it stalled, hiccuped, lost power terribly for the first 8 miles or so. After driving it about 15 miles it was running much better and I had no issues for about 5 more miles before I got home. I never really pushed it but it seemed like it was learning out the issues.

Took it out again today with high hopes and it died pulling away from a stop light. It would turn but not start so I had to leave it OFF for about 15 seconds before it would actually start. I then drove it 5 more easy miles and it seemed just fine.

I am logging with limited knowledge. DAM goes straight to 1, almost zero roughness and going down, a/f was all over the place at first but has stabilized, no knock readings after the first few miles, boost appears to be building well but I have yet to get above 4500 rpm or so.

So, at this point I am wondering if I freaking out over nothing and just need to let the car get used to it (25+ miles though??). I am leaning towards plugs/MAF/sensors all being old just causing the car to take longer to figure it all out?

At least I am somewhat sure the engine isn't being damaged, I think...
 

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Administrator
2007 Forester Sports XT 4EAT
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37,605 Posts
My '07 FSXT didn't like the COBB OTS maps. After contacting COBB, I was referred to a local tuner. That was 10 years ago & I'm still VERY happy when my COBB Surgeline "stock", Stage 1+ dyno protune.

I have all the parts, all brand new, to move on to Stage 2+, but never felt I needed to. Perhaps some day...

Here's a link to my write up in my Member Journal. I requested the tuner to shoot for maximum tq, over maximum hp. The engine is VERY responsive & the pickup is impressive!

COBB Tuning Surgeline dyno protune - Stage 1+
 

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2004 Forester XT
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29 Posts
Discussion Starter #9
Thanks Bobby. Your posts have been super helpful and downright interesting in the years we have owned this car and lurked this forum.

I'd like to make it to stage 2 if I am going to pay for a good tune. Your numbers are great but this isn't my daily so the used cobb AP and the ots stage 1 is about as expensive as I am going to go before I decide to really MOD it or just keep it stock.

Sounds like you might have some parts you wouldn't mind letting go for cheap though;)

I'll probably drive this a couple of days of easy driving, if it doesn't get better I'll pull it off and wait for a good deal on a DP and UP. I can install those myself and throw in some plugs along the way and then pay the pros for a tune.
 

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2004 Forester XT
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29 Posts
Discussion Starter #10 (Edited)
Continuing down the rabbit hole on this..

So I started to suspect a vacuum leak. The car was going real lean right when it was having an event and it was usually just when you stepped on the gas.

I looked through the engine and nothing seemed out of place except the intake tube (stock) was slightly askew behind the MAF. I reseated and tightened it up and the issues completely disappeared for about 10 miles. I'm now running stage one with no issues. I even reset the ECU to make sure it hadn't just learned around the issue.

I felt pretty dumb but was glad it was such a minor issue. I logged it and everything seemed to be in order. Car ran great untill..

The car died on my wife at about mile 20 and started throwing a P0340 (bad cam sensor, bank 1). This is a new code for this car. She says it happened after turning on the radio for the first time. The battery is pretty old, never had issues but I think I am going to replace it just to get that checked off.

Other than that, seems like I either knocked some wiring loose some how, the sensor just failed extremely coincidentally or maybe all the dying of the engine caused the timing belt to skip?? 160k on the engine, we changed the belt at the 105k service.

Still troubleshooting this today. Any ideas would be great. Fun times in fozzy land....
 
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