littlegrn,

Welcome to the site. You must have missed it, but in the top of the Problems & Maint. forum, there is a post that lists all the OBD trouble codes:
http://www.subaruoutback.org/forums/showthread.php?s=&threadid=4908

Anyway P0172: Fuel trim malfunction (A/F too rich)

From the symptoms you mention, it sounds like it's running WAY too rich. I doubt you sucked anything in there, but it might be worth checking your air intake/filter to make sure there's not a plastic bag in front of it or anything. Failing that, my money is on the MAP sensor.

Are you sure there were no other codes on the OBD?

 

Hi littlegrn and welcome!
DTC P0172 - FUEL TRIM MALFUNCTION (A/F TOO RICH)
DTC DETECTING CONDITION:
* Two consecutive driving cycles with fault
TROUBLE SYMPTOM:
* Erroneous idling
* Engine stalls.
* Poor driving performance

Are there holes or loose bolts on exhaust system?

Are there holes, loose bolts or disconnection of hose on air intake system?

Could be fuel pressure regulator issues and/or plugged return line to tank:
* Is fuel pressure between 284 and 314 kPa (2.9 - 3.2 kg/Sq.cm, 41 - 46 psi) at idle in neutral with fuel pressure regulator vacuum hose disconnected?

* Is fuel pressure between 206 and 235 kPa (2.1 - 2.4 kg/Sq.cm, 30 - 34 psi) at idle in neutral with fuel pressure regulator vacuum hose connected?

Engine coolant temp sensor could be faulty
MAP could be faulty
Intake air temp sensor could be faulty

 

No other codes being thrown.
where is the MAP sensor located on an 02 outback anyone know?
Also I changed out my air filter and when i did, I noticed that the air box hadn't been seated properly and had about a half inch gap that anything could have gotten in. I took a look at the butterfly valve on the throttle body and is was caked in oily dirt. knowing that, I am thinking this could be a contributing factor, any suggestions for cleaning out the inside?

also is the MAP the same as the upstream O2 sensor or is it something completely different?

 

MAP is manifold absolute pressure. It is not the same as the O2 sensor. The MAP is located on the throttle body. It says you have to remove the IACV to get at it. It appears to be on the throttle body right in line with where the throttle cables connect. The MAP and IACV have gaskets that should be replaced if it is removed.

You can decoke the throttle plate by removing the throttle body, or I just block the throttle wide open by manually turning the thingy with the throttle cable and using a pair of vise grips to loosely clamp it open. Then spray something like valvoline throttle body cleaner (shouldn't use anything that says only carb cleaner). I use a soft brush to scrub it, but that's at your own risk since some automakers say not to use a brush because it could damage some coating on the throttle butterfly (though I don't think Subaru says that).

Then when starting, hold the pedal down about 1/4" way to let some air in there to get out the cleaner. Otherwise it will take some cranking to get it started.

 

One other thing I didn't think of before, but you might have a loose vacuum hose somewhere. Doesn't hurt to check...

It might be time to bring this one in to the dealer to diagnose.

 

Thoroughly cleaning the throttle body and IACV would be a good place to start on this one, especially considering the black crap on the throttle plate. I would just take the throttle body off and clean it by hand. Just spraying the cleaner in doesn't seem to be a very thorough way to do it - it misses the whole back side of the plate and much of the internal walls. It also won't clean the IACV and air bypass very well. This has been a big factor in similar issues with my car and cleaning it has helped immensely.

 

So I finally got a chance to work on the subby. took the throttle body off and cleaned it and the intake manifold as well as I could. BIG improvement, not sure if I am ready to call it fixed yet because I didn't get much of a chance to test it out yesterday, but from the little bit of testing I did last night it isn't surging, hesitating and has its usual pickup back. Thanks for all your help and I will post again if the problem isn't fixed. Thanks again.

 

Well it worked fine for about a day, now its right back to doing it again. Any more ideas?

 

Any more ideas?

Yes, the info in my first post in this thread is troubleshooting info right out of the factory service manual. I suggest checking those items. The basic things the FSM lists, in this order, are:

1. exhaust leak and/or loose exhaust bolts
2. fuel pressure regulator and/or blocked fuel return line to tank (need to check fuel pressure under two conditions)
3. Engine coolant temp sensor could be faulty - I have seen these go bad
4. MAP could be faulty
5. Intake air temp sensor could be faulty

 

So i broke down and took it to a dealership here in germany. turned out to be the engine was cruded up inside, the 02 sensor was faulty and the auto parts store sent me the wrong spark plugs. Thank to everyone for the help