I didn’t find any cap pieces . . .

Okay. If the coolant was up to the level of the cap, then the part of the first photo (post #3187 above) that I red-circled might just be a reflection in the coolant. I asked because there's a fair number cases here of the black fitting on the cap (second red-circled photo) breaking off and dropping into the upper radiator tank. That black piece is somewhat unique to the Subaru H6 radiator cap.

. . . exhaust fumes are going into the coolant . .

Will have to leave the question of fumes causing the coffee brown state of the coolant to those with more experience. I've only seen coolant that was rust colored, and even at that, still fluid, whereas yours looks to be quite thick. That said, the mixing of coolants made with different base materials has been cited as causing the development of thiick "gunk" which has been found blocking the heater core and causing overheating or poor heating in the cabin.

 

@2005Subi
Those cats are done. You can get away with just replacing the 2 front cats and leave the 3rd in place. Good chance that the 3rd one will not affect setting a P0420 after 2 new front are in. Its not working at the moment because it's being overloaded since the 2 front are toast. Besides that, you won't find a weld in for the 3rd cat.

 

Thanks! I will look at replacing those and getting back to you on the readings. I assume that means the rest of the engine is running generally well?

I looked at the Amazon CATS you sent and had some questions by the way. What is the longevity of those cheap cats generally, should I expect to replace them every other year or every 25000 miles? Is it worth getting a magnaflow cat if it means long term less replacement? And will non CARB parts trip the engine light? I assume the O2 sensors are dialed for CARB components but its suprisingly little information out there on this car I assume cause its a 1/1 in terms of outback weirdness.

 

@2005Subi

Good aftermarket cats will last a lot of miles.

The computer sees feedback from the sensors to determine cat effectiveness. The CARB setup is not the substrate type as much as it is there's 3 cats instead of of 2 for the same size engine that is FED/50 STATE. One cat for 2 cylinders per side then the 3rd is kin to the 2nd in FED.

One of my customers here has had an aftermarket cat on one bank of his CARB car for 5 years and about 60k miles and it still works fine w/o popping a fault. (Welded in)

 

Hi Cardoc, I'm still battling the P0420 from a couple of months ago. Here are a few recent RR files that show the cat is able to do the job when power level (engine load) is above idle, but rear O2 drops when throttle is closed. I've checked many things, ran a bottle of Berryman's B12 Chemtool fed into intake, checked plugs (ref posts 3146-3149, 3152-3152). The new cat is a Walker (from Rockauto) and only has around 7,000 miles on it. I'm going to try returning it since everything else seems to check out (and the car burns very little oil). Do you see anything else that still might be an issue besides faulty cat? (note: coolant temp is in deg C in these...)
Dropbox

Dropbox

Dropbox

 

I'll post back later. I have to get my laptop from the shop to see it clearly.

 

@MikeC5

Closed throttle the fuel is cut, the front AF sensor will show lean, either 20.xx stoichiometric, or 1.3x Lambda, and the rear O2 will show 0.01 to 0.05. This is normal with fuel cut deceleration.

Your logs look okay with exception to a few places where the fuel trim acts up and the rear O2 reflects it. The throttle is remaining steady, so its not an on throttle, off throttle situation. You either have bad grounding or the front sensor is failing, giving incorrect feedback to the ECM.

 

Thanks Cardoc. I’ll check when I installed the front sensor. It could be time for a new one. I have checked the grounds, unbolted and cleaned them. I just checked and AF sensor (Denso) was replaced only around 15K miles ago while the downstream O2 sensor (Denso) was replaced 25K miles ago. I guess a bum AF sensor is possible with low miles. Do you see that sometimes? I'll take a look at the connector and see if anything looks amiss. Do you know which ground point the AF sensor uses? Maybe I missed cleaning it.. I'm also thinking to record a run fully warmed up at idle for a few minutes to better see what it's doing.

 

If the sensor has 15k miles on it, it would be odd that its acting up.

So maybe an exhaust leak, the grounds from the heads to the frame, poor conductance through the main ground and other satellite grounds. I cannot see any reason for the ECM to add fuel like its doing in the logs when the throttle remains constant.

 

Thank you Cardoc for all of your knowledge and help.
You are so helpful to us do it your selfers here.

 

Yes, Indeed! Would an exhaust leak be more likely to cause problems at no/low load vs. under load (as far as rear O2 behavior)?

 

Yes

 

Thanks, Cardoc. I will focus on a potential exhaust leak.

 

@cardoc just wondering I have an intermittent P0420 that Ive been kind of chasing lazily lol, but recently I can hear that I have an exhaust leak and I havent pinpointed exact location but it sounds like its post CATS closer to the muffler. I didn't think that would trigger it but wanted your expert opinion. Thanks!

 

An exhaust leak that far removed from the rear O2 sensor will not affect the sensor feedback or cat function.

 

Hello everyone, I'm new to the forum, to the Subaru world, and also to this beautiful country. I moved to the US from Europe last year and recently managed to buy a Subaru lemon – so far so good!

The car in question is a 2010 Subaru Outback 2.5i CVT with 242k miles on the clock. I bought it from the original owner, and while it has multiple issues, I’m trying to tackle them by priority.

Pulled codes with a Gearwrench GWSMARTBT and found an intermittent P0420. Surprised it’s not permanent since the exhaust smells like a catless car. Funny thing is, the I/M readiness shows the cat passing. Before throwing a new cat at it, I’d like to rule out bigger engine issues.

Service history shows:

• Cat replaced at 200k
• Water pump + radiator at 217k
• Heads redone at 220k after overheating

Since I bought it, I’ve driven about 700 miles. No coolant loss, but a little oil drop. Valve cover gaskets are shot and leaking into the plug wells. Maybe is worth mentioning that the car had ran only with conventional oil. Exhaust has some smoke, but not oil or coolant smell – more like a generator/catless setup.

Attached some scan data for reference. Any thoughts on what I should check before blaming the cat?

edit: I haven't included the coolant temp since it stays pretty much constant

 

Hello everyone, I'm new to the forum, to the Subaru world, and also to this beautiful country. I moved to the US from Europe last year and recently managed to buy a Subaru lemon – so far so good!

The car in question is a 2010 Subaru Outback 2.5i CVT with 242k miles on the clock. I bought it from the original owner, and while it has multiple issues, I’m trying to tackle them by priority.

Pulled codes with a Gearwrench GWSMARTBT and found an intermittent P0420. Surprised it’s not permanent since the exhaust smells like a catless car. Funny thing is, the I/M readiness shows the cat passing. Before throwing a new cat at it, I’d like to rule out bigger engine issues.

Service history shows:

• Cat replaced at 200k
• Water pump + radiator at 217k
• Heads redone at 220k after overheating

Since I bought it, I’ve driven about 700 miles. No coolant loss, but a little oil drop. Valve cover gaskets are shot and leaking into the plug wells. Maybe is worth mentioning that the car had ran only with conventional oil. Exhaust has some smoke, but not oil or coolant smell – more like a generator/catless setup.

Attached some scan data for reference. Any thoughts on what I should check before blaming the cat?

edit: I haven't included the coolant temp since it stays pretty much constant

From what you've posted, the cat isn't working. The rear O2 sensor is reacting seen by the voltage output at higher rpm in the 4th graph; it goes high and stays there when the ECM is running richer fueling and comes back down when it switches to normal fueling.

If there was a head gasket problem previously and coolant was being burned it will affect the cat.

What color is the smoke? Black is unburned fuel. Blue is oil. White is water//coolant.

Have you checked the spark plugs?

How old is the battery? Are the grounds good?

Are you using good gas? No Walmart, no Sam's club, no mom/pop stations that tend to have slow tank turn over.
I'm not seeing in the data you posted any issues with the front sensor.

The Cat Monitor setting just means that the ECM has run its tests on the cat function and the monitor is ready. The pending fault is after the monitor set.

Try this - get a bottle of Berryman's B12 Chemtool and poor it in the gas tank and drive it. As long as the tank is 1/2 full or more, it's good. After running the tank to a low level and filling again, look at the data again to see if it changes.

 

Thank you for your reply!

I've attached a picture with one of the spark plug. From what I've seen, is not the right one for the car. I will replace all 4 and the cover gasket.
The gas is from Mobil gas station. The smoke I would describe it as grey. I don't know how old is the battery.
I will try what you've suggested and post back!

 

Hey cardoc, I have an issue and I was wondering if I could possibly get some advice. I have a 2012 impreza that is throwing the P0420 code. It has been driving okay until yesterday. I just replaced both o2 sensors (both of the old ones were chalky white), but the car is still idling rough and almost sounds like a train chugging like it can't breathe. I am assuming the cat is clogged and needs replaced but I'm not sure if there could be another fix im unaware of.