blew_by_u

The short question is,

are there any OTHER causes to a POSITIVE pressure when I remove the oil cap (pressure you can feel with your hand) than rings or valves?
This might be a stretch: could the 2.0L, 16V have maybe a bizzarre EGR issue? Something with the air-bypass valve maybe? I know these SHOULD be completely separate of the crank case.

The LONG HISTORY as I know it:
I go the car 2 year ago, it passed smog - and 8 miles later the check engine light came on. I thought the problem went away, but actually only the bulb burned out.

Now, 75,000 miles later (a lot of driving/Uber), I looked in the FSM someone was nice enough to post. P0421 - something about cat inefficiency. Could be bad O2 sensors, Or the cat. There is trouble shooting method to differentiate.

Not having the skills to measure the voltage across each sensor to diagnose the sensor or the cat, I opted to replace the O2 sensors since I'm lead to believe they are expendables anyway.

That didn't make the code go away. I then learned even if that had been the problem, the code has to be physically cleared and doesn't just go away after x number of cycles without the problem being present. So I cleared the codes. The sensors weren't the problem: the code is still there. [I can't say I like or believe the smog guy who asked 'what kind of sensors?' Bosch. Can't believe Bosch would make junk if its the right sensors.]

I did have the pipe off the manifold some time ago to replace that gasket that was burned out to the side. I think I remember the element in the cat being all white? Don't recall if I could see openings in the element or all sealed?
I think I've since learned: bad O2 sensors can make the PCM try adjust - until the cat is damaged? Either way, I guess NOW the only thing left for that code is.. try a new cat?

But I don't want to stick a new cat on.. an engine that is shot? That pressure out the crank case..
The engine isn't burning any oil. I'm not going to bother with a leak-down test b/c if it needs rings or valves - I'm done with it (the car has a salvage title making it ok to drive, just not to make major investments in).
And its a California car: that is one expensive exhaust manifold/cat.

If the cat is plugged..
could that contribute to the gasket on the exit from the manifold/cat blowing out? Could it contribute to the pressure in the crank case?
I like the car and can only imagine how fun it would be if it ran well - though I did just get 33mpg on a road trip this weekend.

ADDITIONAL FUN FACTS:
I've been through 3 sets of motor mounts in my 75k miles. There has always been a vibration present, more so immediately as the rpm increases off idle.
Now that I discovered the possible compression blow-by, that vibration feels connected.

Also, at one point when the idle was rough to the point of stalling when I put the car in park, after changing plugs, I cleaned the airflow sensor and throttle body with the appropriate cleaners. The idle smoothed out to the point that, immediately after that (but only occasionally and for a brief time) I'd come to a light and the idle would be so smooth and quiet, I'd swear it must have stalled (it didn't).
As I said, that didn't last long. Mainly it feels like I'm driving a Mitsubishi diesel delivery truck. Not fun. But the point of this is, the condition seems to be transient, not permanent like a bent crank would be.

I tried unplugging two seperate connections on the throttle body, thinking one might be the air by-pass vavle if that changed anything (no change). To my amazement and surprise, the car even runs (not sure how long it would run) - with the connection to the throttle body unplugged???

And I've never changed the timing belt. It looks ok, though I'm told it can stretch slightly throwing the timing off slightly?

Any thought/advice from those more knowledgeable would be greatly appreciated.

CrAnSwIcK

iTrader: (5)

thanks for keeping it short...

the short answer is, check your PCV valve is working, positive crank case pressure is normal, and is dealt with via the PCV valve, make sure there are no other exhaust leaks...your blown out gasket would be an exhaust leak, which could throw codes for cat efficiency. which oxygen sensors did you replace?

have you check the compression, how have you come to the conclusion that your motor has excessive blow-by? Also a faulty evaporative emissions purge solenoid can cause the engine to stall at idle, and make it difficult to start on a full tank of gas. ANY other vacuum leak can and will cause issues with idle and stalling. So also check for any vacuum leaks. do you have a scanner? have a look at the live stream data, and make sure you IAT and MAF readings are normal.

OZR_Lancer

iTrader: (2)

if you have P0421... since you have changed the o2 ( one thats on the header ? ) more than likely its the cat thats built into our oem header... i went thro the same damm thing as you and it was the header that was bad...

more than likely you will have to replace the header on your car cause the cat is built into it and is fried... that part alone is $500 for a carb legal one since we are in cali..

i replaced mine last year ....

blew_by_u

Thank you both for the replies!

Ok I am now amending my thoughts: some blow-by in the crank case is normal.
the pcv valve rattled when I took it out. I sprayed throttle body cleaner, shook it rinsed it, it rattles even better. And pulls vacum when connected. So I'll assume it works?

And the blown out gasket.. I'm thinking it's burned out again. I get this little birdie chirping sound, and it looks like gases may be leaking where the manfold and pipe meet. For whatever my visual opinion is worth.
I replace both the up and downstream sensors. So probably a new cat (will solve the gasket problem too) will be the answer.

Never had a problem starting, so I hope that means the evap system and canister are ok. But I will check carefully for vacum leaks.

Live scanner, IAT and MAF readings are not in my skill set yet. Unfortinately not even the time to figure those out.

Thanks again!

CrAnSwIcK

iTrader: (5)

too bad you live in California, those cats are expensive...

blew_by_u

To end this story, it was the cat. It was all white (additives in the gas I'm told by the Bosch tech people). I found the exact, California cat new, the complete kit (hardware/gasskets) for I think $325 on Amazon. The card in the box said mitsubishipartscentral.com. My guess was possibly inventory from a dealer when the financial crisis hit and dealerships closed?
But it was identical to the factory piece, the codes are gone, and I passed SMOG!

'California catalytic converter'
'California exhaust manifold'
'California cat/manifold'

If anyone knows how to add useful tags to a post - I'm happy to learn.

beetle_orange

iTrader: (58)

I have this code on a 2006 lancer.

While browsing Craigslist I saw a 2002 with headers, owner said it was from magnaflow.

Is this something I can use instead of going back to OEM? Would anyone know where to get this headers?

CrAnSwIcK

iTrader: (5)

You will get the same issues with headers, unless you either space the oxygen sensor, or disable it.