P0172, P1137 and P0301-304- Baby Steps Please

[SteveKoz]

Hi.. Looking for some direction. Took my son's 2002 Outback for a ride to the store. CE light was on but the car ran fine. Got half way there before she stared acting up. Almost didn't make it. I stoped at the autoparts. It had 6 codes.. P0301 - 304 -Cylinder misfire on all 4 cylinders.. Followed by P0172-System to rich Bank and then P1137-Front Oxygen sensor. I'm thinking I can rule out the P0301 - P0304 as a bi-problem to the P0172 or P1137. I've searched on here and read a lot about thhe P0172 but I'm still lost. Need some baby steps type of help. Where do I get started? Check for vacuum leaks? How? If I had a leak I would think the engine would run bad all the time. How can I find out where to find the front oxygen sensor? Is it cleanable? Can someone point to the oxygen sensor in this picture? Is it even in this picture..

Any help is appreciate.

Thanks!

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[feint05]

more information on the car and condition please? mileage, recent repairs etc

a bad front 02 sensor can cause tons of problems, it tells the engine how much fuel to put in so that can cause misfires and running rich, take it out give it a lookover, check all the wiring attached etc, a new front one will run you 100+

[RaceFaceXC]

And to answer the rest of your question, the front O2 sensor can be found on the exhaust manifold or the catalytic converter pipe, which is located just aft of the exhaust manifold. It will be before the cat, in terms of exhaust flow. There will probably be a rear O2 AFTER the catalytic converter and it should not cause these problems so I wouldn't even touch it.

The front O2 sensor is not cleanable. Although many have tried very few have had any good results.

www.subarugenuineparts.com will be amongst the cheapest prices for oem parts. A dealer will charge 200+ with parts to replace the front O2.

[SteveKoz]

Thanks for the replys. It's a 2002 Outback with 80,000 miles on the odometer. It's has a replacement motor. It's not a new motor but a replacement with about the same miles. We haven't done any mods to it in the last 7500 miles and it was running great. According to my son the first codes he saw was the misfires on all cyls.. When I pulled the codes I saw the P0172 and P1137. I called the local auto parts and they sell an O2 sensor for $66. Is that the first place/part to change? I'm wondering if all cyls misfired would it be more likely a coil pack? With the misfires I could see the O2 sensor tripping a code. Not sure how the P0172-System to rich Bank code would get thrown. Fuel not burnt because of the misfire maybe? Mechanic said to check the plugs but again, ALL cyls are tripping codes and it seems unlikely that all would go bad at the same time. I don't want to just throw money at parts without a logical reason. So what would be the first logical part?

Thanks!

[RaceFaceXC]

the 02 sensor basically dictates how much fuel will be injected when operating in "closed loop" mode. If the sensor goes bad and causes too much fuel to be injected resulting in a super rich condition, it can cause a misfire. (and usually sluggish performance until 3k rpm or so when you floor it from a slow speed)

There is a range of fuel to air ratios that are flammable. outside that range, the mixture will not support even, rapid combustion. And only 1 parcel of fuel will burn for every 14 parcels of air, so if there is too much fuel and not enough air (O2 to be more accurate) then once the O2 is all used up the extra will go out the exhaust valve and into the exhaust. All 4 cylinders are getting fuel from the injectors which are all controlled by the ECU (engine computer). If one injects too much fuel, they all will. Individual cylinder fuel management is only on very new, super low emissions and high performance vehicles right now.