P0420 code and issue with oil

[amtrack]

I have a 2007 subaru outback. 203k miles. Timing belt was changed in dec 2013. since April we have had issues with the oil. Right before due for an oil change around 2k the oil would just disappear and the check engine light would come on showing P0026 and p0028. We would change oil filter and oil and itd do fine act normal light went off until abt 2k again changed it again used better oil and filter lasted 3k before light came on. This last oil change we threw in some lucas suppliment oil also. Now check engine light is reading same codes and P0420. Catalyst below threshold. any idea to whats wrong? it holds this oil til tht very last moment then its gone.

[Gloyale]

I doubt the codes are related to your oil changes.

 

Check engine light does not monitor oil level.

[idosubaru]

P0420 is benign or simply and artifact of the poor running engine.  definitely ignore that for now, you can drive a car for 100,000 miles with that code, no big deal.

 

oil loss and P0026/P0028 could be serious issues - you may have oiling issues which can essentially render an engine useless very quickly.  i would look into this quick.

 

all we have is words, choose them carefully as we aren't as fortunate as a local shop to see the vehicle.

 

describe exactly what's happening:
 

1. you say "disappearing", this would mean no oil at all, that's impossible as the engine would lock up, so let's guess what you mean...

 

2. i assume you mean it is exactly up the full line at 1,999 miles and then doesn't register on the dipstick at 2,000 miles?

this also sounds nearly impossible. 

(when there's no oil on the dipstick, that is alarming but there's still oil in the engine).

if it literally goes from ***completely full*** on the top mark of the dipstick to not registering at all between 1,999 and 2,000 miles then you have a very sick person who doesn't like you that's tampering with your engine.  lol, just kidding.  that is alarming and needs to get diagnosed immediately.

 

3.  if you're loosing a lot of oil - quarts at a time, multiple times - then it has to be going somewhere noticeable.

 

A.  look under the vehicle for oil leaks.  if the undercover is on - it needs to come off.

B.  look at the rear of the engine - back where it mates to the transmission.

C.  pull the spark plugs and check condition - for severe fouling or oil in the spark plug tubes (caused by spark plug tube gasket leak).

[amtrack]

Sorry I should have described disappearing better. What I meant was we check it at least once a week if not more and within that week It will go from five quarts to close to none at all. we can not see any visible leaks and there is no oil in the exhaust pipe.

[1 Lucky Texan]

well, it isn't clear the oil level is being checked correctly or on any type of schedule so, make certain the car is level, if it was just running, wait 5 minutes or more,  pull the stick and wipe it, wait a minute, insert the stick fully, then check, look at both sides of the stick. Do that again to see what the reading is on average.

 

Consider changing the PCV valve. Whent the timing belt was doen, was the engine removed from the car or any other work done?

 

Has the oil pan been dented?

 

what brand and weight oil is being used?

[idosubaru]

Sorry I should have described disappearing better. What I meant was we check it at least once a week if not more and within that week It will go from five quarts to close to none at all. we can not see any visible leaks and there is no oil in the exhaust pipe.

 

if you're loosing 2 quarts of oil it's simply external or internal. 

 

1. inspect carefully - it should be leaking it externally somewhere. 

*** Have you checked EVERYWHERE - removed any undercovers if it has one - to check? 

 

2.  it's leaking internally - in that case you need to do a leak down test, pressurize the cylinders and finding out where it's going.  fairly rare for this engine to do this so hard to say what would be likely.  piston rings or valve stem seals are "standard" internal oil loss areas.

 

the dipstick doesn't go to the bottom of the pan, so when there's no oil on the dipstick there's still tons of oil in the pan.  when the oil is not showing on the dipstick - you can add oil and see how many quarts it takes to get back to full - that's how much it's low.

[Fairtax4me]

P0026 and P0028 codes are for the variable camshaft timing solenoids. Specifically these codes are for the low oil pressure switches located on the solenoids. If the oil level gets low enough these codes may trigger because of a lack of oil.

The difference between "Full" on the dipstick, and not showing at all is about 2 quarts. I would guess you're losing closer to 3 quarts of oil based on the codes above.

 

2 quarts in 2,000 miles could easily be from a bad PCV valve or clogged PCV hoses. You may be losing more due to external leaks such as the separator plate or valve cover gaskets.

 

P0420 can be caused by a clogged PCV valve or hoses since this causes excessive amounts of oil to be forced into the combustion chambers and burned off as you drive. Oil affects the burn rate of the fuel/air mixure and can damage the catalytic converters.

[Gloyale]

2006+ engines also have the weird triangular basin oil pan......

 

Wonder if the shape of the pan could make a steady rate of oil loss appear to accelerate as the level drops.

 

At the top of the pan.....a loss of say half a quart, would be only a slight drop.....but as the level drops more......the pan is smaller towards the bottom.......so that same 1/2 quart loss, shows as a bigger "drop" on the stick.

 

Just a guess....

 

I'm thinkin you might want to have the screens behind those solenoids cleaned/replaced.....