[BewareTheHooks]

Hey all, ever since going catless I have been experiencing blue smoke whenever I have been idling for an extended period of time. At a stoplight, it will take about a minute before it will consistently spew moderate amounts of smoke from the exhaust. I don't know what the issue can be since it doesn't occur while driving normally, so I am wondering if anyone would be able to offer any knowledge or expertise on this situation.

Mods
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Invidia Catless DP
Invidia N1 Catback
Stage 2 Tune by TorquedPerformance

 

[a5m]

Not having a cat will not make a car burn oil, which is indicated by blue smoke. That's unrelated. Maybe the freer flowing exhaust is making it more visible now.

What car and year? Have you replaced or checked the PCV Valve? Have you done a compression and leak down test? Have you monitored how much oil it burns?

 

[BewareTheHooks]

Thank you for the response. I have a 2014 wrx and I have not replaced the pcv valve or lines. I have actually been planning to do a comp and leakdown test, but I’ve been pretty busy lately so I haven’t been able to find a time to take it in for the tests. So far oil consumption has been about 1 quart for 3,000 miles but I have no clue on what’s considered normal.

 

[a5m]

No worries. I think 1qt/3k miles is just outside what Subaru considers normal oil consumption. I personally feel that's excessive. I'd look into replacing the PCV Valve and any lines that are hard or brittle, which will probably be all of them if they've never been touched. These often get overlooked and can be the cause. Good chance your PCV Valve is original and need of replacement.

I'd probably get the compression and leakdown test first just to see where things stand. Avoid throwing good money after bad.

 

[BewareTheHooks]

Okay, I will. I actually forgot to mention that I had the engine rebuilt less than a year ago which makes it an even weirder situation. I believe that they did mention that the PCV system was getting a little hard at that time so your advice seems to line up with that. It’s just a thing that kinda slipped past me since I have been working on replacing wearing suspension components. I definitely appreciate your input on this.

 

[zax]

When it comes to oil consumption, a leakdown test provides more useful information than a compression test. You should sweep each cylinder over TDC during the leakdown test and watch the pressure output - this will tell you if the rings are unseating when the piston changes direction. Another classic trick to separate valve failure from piston/piston ring wear is to do a compression test dry, then squirt some oil in the cylinders and see if the compression increases.

If leakdown is good, check valve guides and then suspect turbo seals.

Is there oil in the intercooler?

 

[killerbmotorspo]

I would start with replacing the PCV Valve. It's cheap and easy. Then move on to the hoses and then any and all vacuum lines for being in good condition of free from clogs.

Compression and leak-down test is more of a commitment, but will give some good info in regard to the health of the engine. If it's fairly new, it should be good.

Turbo seals are least likely but are still known to cause issues on higher mileage cars.

 

[BewareTheHooks]

When it comes to oil consumption, a leakdown test provides more useful information than a compression test. You should sweep each cylinder over TDC during the leakdown test and watch the pressure output - this will tell you if the rings are unseating when the piston changes direction. Another classic trick to separate valve failure from piston/piston ring wear is to do a compression test dry, then squirt some oil in the cylinders and see if the compression increases.

If leakdown is good, check valve guides and then suspect turbo seals.

Is there oil in the intercooler?

Hi zax, I remember you helping with one of my last posts. I have considered doing the leakdown test myself but I have never done it before and I feel a bit intimidated by it. I have looked around and they are asking around $300 for both a comp and leakdown test, but I just haven't had the time to bring it in. The last time that I took the intercooler and throttle body hose off I did notice some residue. I just assumed that it was standard blowby as I have not installed an AOS yet. I will include some pictures once I get home to give an idea of how it is looking as that would probably mean more than a rough description.

 

[BewareTheHooks]

I would start with replacing the PCV Valve. It's cheap and easy. Then move on to the hoses and then any and all vacuum lines for being in good condition of free from clogs.

Compression and leak-down test is more of a commitment, but will give some good info in regard to the health of the engine. If it's fairly new, it should be good.

Turbo seals are least likely but are still known to cause issues on higher mileage cars.

True, I was planning on doing the valve itself this week since it is a pretty simple and cheap procedure to do myself. I have not been running the engine rough or neglecting the maintenance so I'd hope that it is in good condition.

 

[BewareTheHooks]

Hi zax, I remember you helping with one of my last posts. I have considered doing the leakdown test myself but I have never done it before and I feel a bit intimidated by it. I have looked around and they are asking around $300 for both a comp and leakdown test, but I just haven't had the time to bring it in. The last time that I took the intercooler and throttle body hose off I did notice some residue. I just assumed that it was standard blowby as I have not installed an AOS yet. I will include some pictures once I get home to give an idea of how it is looking as that would probably mean more than a rough description.

 

[killerbmotorspo]

Those pics look pretty normal for a car with some mileage. Usually if you put the intercooler on end, and oil drips out, there is likely an issue.

Make sure you are replacing gaskets when you re-install

 

[zax]

Agreed. Looks fine.

 

[BewareTheHooks]

Those pics look pretty normal for a car with some mileage. Usually if you put the intercooler on end, and oil drips out, there is likely an issue.

Make sure you are replacing gaskets when you re-install

Okay, that’s the response I was hoping for lol. I’m hoping to swap out the PCV Valve today or tomorrow so I will give an update afterwards. Also yessir on the gasket thing, I’ve made it a habit to replace any gaskets that I mess with or take off.

 

[mjtct]

Yes on the PCV but could it somehow be your turbo leaking oil? Did your cat show any signs of oil? Im not sure but seems the cat removal will impact back pressure.