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Discussion Starter · #1 ·
Newbie here. Great site! Thanks to all who contribute.

I thought I would share my story of woe in hope that someone may be able to shed light on the cause of my problem.

Car: 2006 Outback XT (turbo)
State of tune: Car is 100% stock
Miles: 66k
Type of miles: Local ( rural / non-highway) miles
Driver: single driver / middle aged mellow.

The short story:

The car started running a rough at low idle. OK on start and higher RPM. Shortly thereafter, it threw the CEL and flashing cruise light.

I did the trip meter / headlight dance to to pull the codes from the dash. Came up with the following:

P0302 - Cyl 2 misfire
P0000 - ?
P2096 - Post Cat fuel trim system too lean bank 1

Since the car was overdue for the 60k tune, I hoped the fix would be simple. Dealer checked plugs, boots, coils, etc. - no luck. Performed a compression test and saw low compression on Cyl 2. Leakdown test pointed to valves.

Took car for second opinion - same result.

Had a local independent pull the heads and they passed them on to a car racing engine shop. I called the shop direct to get the story from the guy working on the heads. Here are some of his comments:

“The valve seats were beat up.” Intake valves were OK but the exhaust valves were beat. Problem is likely heat from the turbo.
“1 valve was the problem child but all exhaust valves were beat to heck!” If we had only fixed the one valve, the car would have been back in the shop soon.
Looks like the exhaust temps are too high. Maybe the fueling is too lean?
You may want to check with a Dealer to see if there have been any updated to fuel mapping. Maybe find tuners that can bump the fueling a point or two. That would probably fix your problem.

OK. Besides making me feel great about my car (which I have babied), he made me consider how this could have happened.
Questions:
1) How can a stock car be running lean? Don't most OEM cars run rich for lower cyl temps and better reliability?
2) Have there been any updates to the ECU fuel mapping since 2006?
3) I don't know if the turbo is considered a performance engine or not but is it possible that not driving the car hard enough could cause damage? This damage?
4) I see from an old thead on a similar subject that "Seabass" mentioned the following:

"I've never heard of it happening with a stock tune. Something is not right because the stock tune is ridiculously rich and this shouldn't happen. Make sure the mechanic double checks all of the vacuum lines when putting it back together. There is a vacuum line that is known to pop off if bumped while you're working in there. It will make the car run very lean and possibly wreck your engine. Could be what happened in your case."

Can anyone provide additional information on this vacuum line that can pop off?

Thanks
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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I doubt I'll have much to offer but;

was any work/mods done before the problem began?

do you run premium fuel?

did anyone look at FreezeFrame data? (STFT etc.)
 

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Discussion Starter · #3 ·
Lucky Tex,

No mods of any kind.

Yes, I run premium fuel. May have seen a total of a half a dozen tanks of midgrade over its life.

No freeze frame data that I know of - not really sure what that is.

The rebuild is underway so all I am really trying to do is understand why she is running so hot - if that is indeed the problem...

Thanks.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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the FF data can be retrieved with some scanners when a code is set. Soob dealers and mechanics (and some enthusiasts) have other tools that read the same and more info about Short Term Fuel Trims and other data. Might tell us if the ECU was trying to pull fuel or deal with other issues that might help diagnose the car.

There's a good chance that just repairing the heads will not address the 'causative' problem.
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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Fuel mapping is programmed to keep the fuel/air at stoichiometric, 14.7:1. Turbo or non turbo engines use sensors to calculate the amount of air coming in to the engine so the fuel injector pulse can match the air flow to reach stoich. On yours, its a MAF, mass air flow sensor. The "map" in the ECM is preset to add or reduce fuel delivery based on the information from the MAF. At the same time, the ECM varies the fuel trim slightly from rich/lean to control the temperature of the CAT. It verifies the mix using data from the AF sensors and will make adjustments based on the AF data.

When air enters the engine anywhere after the MAF, it throws the math off. Lets say at 2k rpm, the MAF is reporting 2lbs of air entering the system. The ECM calculates the fuel mix according to the 2lb. But if there is a leak and more air is coming in than what the ECM sees, its lean. The amount lean is dependent on how large the leak is.

Valve damage indicates a large leak or running lean over a long period of time. On turbos, it can be difficult to find a leak without pressurizing or smoking the intake system because the turbo forces air into the intake. The leak can be anywhere in the intake circuit from the MAF to the heads. On systems that return the bypass air back into the intake system, the bypass tube/hoses need to be checked for leaks.

Another thing to look at is a slow or stuck AF sensor. If the computer is getting "rich" data from the AF sensor, it will reduce the fuel delivery to get down to stoich.

Fuel delivery is another possibility. If the fuel pump can't keep up with demand, the engine runs lean even though the ECM is running the injectors properly.

There may be an issue with fuel delivery. I say MAY be an issue because cylinder 2 is on the end of the fuel circuit before the fuel returns to the tank. So flow of fuel runs in order 3,1,4 then 2. If flow is down, 2 suffers the most and will run lean.

Repairing the valves is necessary, but unless the issue causing lean is found, it will damage the valves again.
 

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01 Outback LL Bean
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Most likly your issue is this issue which affects the 2004 - 2008 2.5i Turbo motors. Weak fuel injector problem is the culprit. I would have all injector's professionally cleaned and flow tested. I like whitchhunter injector cleaning. They will bench flow them before cleaning. I bet injector #2 will stick out.

Rear more here.
Subaru Repair Seattle, Subaru Service Seattle - Seattle Subaru Repair
 

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Discussion Starter · #7 ·
Tex -

Thanks for the info. I agree that repairing the heads is step one. I definitely need to get down to the root cause of the problem.

Cardoc -

Very help information - thank you for the education.

So it looks like I need to check / do the following:

- Clean MAF
- Clean injectors
- Check air intake system for leaks
- Check fuel pump

Does this look like a good list to start with? Any other suggestions?

Thanks again for all your help!
 

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2014 Outback 2.5i SAP Carbide Gray
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valkyrie03 - I have EXACTLY the same issue now on my 2006 outback xt. Rough engine at idle and a check engine light - code is for Cyl2 misfire. Dealer recommends a valve adjustment but just took it to a very well respected subaru tuner for a second opinion and he said the valve adjustment most likely won't fix the underlying problem. Any resolution to your issue?

Thanks!
 

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Newbie here. Was searching and trying to do some research for my 06 OB XT. Same exact problem as you were talking about - albeit many years ago. It's a shot in the dark but did anyone find a resolution to the problem?
 

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Fresh Out of Outbacks!
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It's a less common way for an XT to die, but it does happen.

From my own research, the car is built right but the ECU programming wasn't the best. This problem can be cured by a tuner. Have them create a new fueling map and it won't get you again.
 
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