Boost leak test leak out the breather

[caseclipsegst]

Recently I've had either fuel cut or bad bag bogging at wot so I decided to do a blt. I did the blt through the turbo and air was coming out the VC and breather. I boosted up to 15psi and the air would leak out within 10 secs. I pulled the pcv and I blew through it both ways and air came out from both sides. So I plugged the hose coming from the intake to the pcv and no more air to the VC or breather so I guess bad pcv but could this have caused the fuel cut/bogging effect?

 

[boost97gst]

It could have caused a problem. Replace the PCV, get a 3/8" kynar check valve and put that in-line with the pcv. No boost will make its way into your crank case from THAT area anymore. Then as long as you dont have terrible rings or somehow blowing air past a turbo seal in to the drain, you should not have a crankcase pressure problem anymore.

Edit: Woooooops, you said breather. smh. i hate those things. Yes, in that case, you were blowing metered air right through the valve cover and out through that "cool" breather filter. You were running very rich. Put the new pcv and kynar valve or just the kynar valve alone and you wont have the problem anymore.

 

[caseclipsegst]

Could this have caused the fuel cut/bog symptoms

 

[kenamond]

Could this have caused the fuel cut/bog symptoms

If you have the stock VC breather setup, then it shouldn't affect air metering. The VC breather is supposed to let excess pressure in the crank case escape back into the intake tract *post metering* (after the MAS) when you're under load (boosting) and the PCV valve is closed (only other way out of the crank case with closed PCV is VC breather or dipstick tube). If you have altered your VC breather setup such that it doesn't re-route *all* vented gas back into your intake *after* your MAS, then you'll lose metered air, so your ECU thinks more air is going into the motor than actually is. If it's really bad, your ECU will "fuel cut" which is based on too much air going through the motor than your injectors can support.

If you fix your PCV valve (agree with the check valve upgrade) such that the PCV doesn't leak (unscrew the PCV valve from the VC, leave the rubber line on it, do the BLT and see if air comes out of the bronze nipple end of the PCV valve) at 15psi (I do 30psi BLT and I'm only at 15psi boost), then that part of the puzzle is fixed. This assumes you have a sealed connection between the PCV valve and the IM. Then see if you still leak out the VC breather in a BLT with the PCV reinstalled. If so, it's bad compression (ring blow-by), leaking intake valve stem seals, or maybe a leak past your turbo compressor seal (past the seal, into the CHRA, through the turbo oil return tube, and back to the crankcase at the oil pan (you'd probably hear a lot of bubbling during the BLT if this is the case...a bit of bubbling...one or two "bloops" per second...is normal).

Low compression could help with VC breather BLT leak identification. Bad intake valve stem seals seem to be the final culprit if all else is okay.

I type too much.

EDIT: re-reading your original post. If it took 10 seconds to leak down, I doubt this could account for fuel cut or bogging. However, either get an OEM PCV valve (AutoZone/CarQuest valves don't hold back the boost) or get a check valve as recommended and get your intake to hold (I hold 30psi with no noticeable boost drop over 30 seconds). Boost leaks aren't going to help anything. Then see if your problem is fixed or not. Go from there at least knowing it's not a boost leak.

 

[boost97gst]

I think what we really need to know is if the port on the side of your valve cover has a little filter on it or is it the stock hose that recirculates back into the intake pipe pre turbo.

If you have the neat little filter thing then yes, running super rich on boost could cause missing which may feel like a fuel cut. I really dont know, never had it happen.

If you have the stock hose that routes back into the intake then your problems lie elsewhere. Most likely. In any case you need to fix the pcv first then report back. You have a known problem. As soon as you get one thing taken care of we can follow you down the troubleshooting path.

EDIT: Let me be perfectly clear: Get rid of the filter if you have one and route it with a hose back to the intake pipe. Heres why. Even when you fix your crankcase pressure problem(which is no doubt the pcv) you will have unmetered air entering the system when youre NOT in boost. Causing you to possibly run a tad lean. Not a big deal but also not ideal.

 

[kenamond]

I think what we really need to know is if the port on the side of your valve cover has a little filter on it or is it the stock hose that recirculates back into the intake pipe pre turbo.

If you have the neat little filter thing then yes, running super rich on boost could cause missing which may feel like a fuel cut. I really dont know, never had it happen.

If you have the stock hose that routes back into the intake then your problems lie elsewhere. Most likely. In any case you need to fix the pcv first then report back. You have a known problem. As soon as you get one thing taken care of we can follow you down the troubleshooting path.

EDIT: Let me be perfectly clear: Get rid of the filter if you have one and route it with a hose back to the intake pipe. Heres why. Even when you fix your crankcase pressure problem(which is no doubt the pcv) you will have unmetered air entering the system when youre NOT in boost. Causing you to possibly run a tad lean. Not a big deal but also not ideal.

An *in-line* *closed* filter in your VC breather line is okay as long as it's not clogged (I run a cheap NAPA GM fuel filter in-line). If it has any opening such that air can escape, that's not good (some catch can setups are like this and are inappropriate). All air from the VC breather goes through the filter and back to your intake pipe...otherwise it's not set up correctly. But you can remove the in-line stuff and route it back to your intake pipe just to see if it fixes your problem. If so, the in-line filter is leaking metered air and needs replaced/removed. If not, you might keep the filter. I like the filter because it keeps oil vapor from recirculating from the VC back to the intake pipe, into your intercooler, etc. coating everything in oil.

 

[boost97gst]

yea, that goes without saying. Sorry if i confused the OP. Ken is correct. Filters, catchcans, etc are ok as long as point A goes to point B with no way for air to enter/escape. As long as its in line, all good. Whats very common to see however, is guys running a pcv system like normal and then putting this little filter on the side of the valve cover to vent pressure. Instead of routing it to the intake pipe(via catchcan,filter or nothing at all) Thats not an "ideal" setup.

 

[caseclipsegst]

Yea I have the cool little filter.. so looks like ill be routing it back to its original way

Kenamond I'm running the maft setup does it matter if I have the line comin off the VC to the intake as it will be before the maft sensor

 

[kenamond]

Yea I have the cool little filter.. so looks like ill be routing it back to its original way

Kenamond I'm running the maft setup does it matter if I have the line comin off the VC to the intake as it will be before the maft sensor

I'm not MAFT-knowledgeable, but I'd imagine that if the air was metered on its way to the IM and then it's lost out the VC, it has still been metered and the ECU will inject too much fuel. But let the MAFT experts tell you the real deal.

 

[boost97gst]

You still need to recirculate it. If you're worried about oiling up your turbo inducer/IC piping then get a catch can and put that in line. As Ken said, you're still losing metered air with that filter venting to atmosphere. Also you're sucking in UNmetered air while idling or cruising. You can pick up a cheap catch can, cut it apart and "upgrade" it with some better baffling.

TBH? Once i put in my check valve I didnt have to use a catch can. Ive not seen any excessive oil at all on the inducer or any of the IC piping ive checked. It just wasnt blowing that much oil out.

You have a plan now so youre good to go. Easy fix bud. Bet your driving issues on boost go away too!

 

[caseclipsegst]

Thanks so much guys!!! ill get started on the little fixes and report back with results..

 

[kenamond]

Thanks so much guys!!! ill get started on the little fixes and report back with results..

No problemo.

The simplest solution on the VC breather end is to just run a vaccuum tube from VC breather to intake pipe. An in-line filter can be added later once you fix all of your problems.

On the PCV end, your local autoparts store's PCV doesn't effectively shut off airflow from the intake manifold when you're boosting.

Think about it; your intake manifold under boost is very high pressure (roughly boost pressure) while the inside of the valve cover is at crank case pressure - roughly 0psi gauge pressure (i.e. relative to "outside"), so air wants to flow through the PCV valve into the valve cover. The PCV valve *should* close when this happens; otherwise, your turbo is "boosting your crankcase" which is bad; your crankcase isn't supposed to be overly-pressurized. You stated that the PCV valve flowed both ways. It should be one-way: *into* the valve cover. Assume that you're idling or just started the car and are ready to haul ass to work. Also, let's say that your motor is cold so the piston rings haven't expanded, and your rings have a big gap. Then you've got a lot of blow-by, and this "leak" past the cold piston rings raises your crankcase pressure. In that case, the intake manifold is under vaccuum (at idle or during a shift, the throttle is closed and the engine is "sucking on a brick wall") but you have blow-by gases leaking past the piston rings into the crank case increasing the crankcase pressure and dumping fuel-air mix and exhaust fumes into the crank-case, thus contaminating your oil. Then, you want the PCV valve to open and let the blow-by gases get sucked out of the crankcase (the part of the motor down by the oil pan or under the pistons is directly connected to the top of the motor, under the valve cover via oil galleys. This gas is (normally) sucked out through the PCV, back into the intake manifold, and into the motor to be re-burned). So under load, the PCV is closed and the VC breather deals with crank case pressure (all excess is run back through the motor...including excess oxygen the ECU thought it was going to burn. Under idle or during shifts, the throttle body shuts, the IM goes to vaccuum, the PCV valve opens, and gasoline- and exhaust-gas-ridden fumes get sucked out of the crankcase via the VC breather. So the PCV (Positive Crankcase Ventilation) system deals with excessive crankcase pressure while also cleaning out the nasty fumes from the crankcase.

You have two options for your PCV valve: (1) get an OEM PCV valve from your local Mitsu dealership (the OEM PCV valve properly closes and seals under boost, the local carparts store's version does not) or (2) put an in-line check-valve between the intake mani and the PCV valve (and then you can use the cheap autoparts store PCV valve, because the check valve takes up the role of blocking boosting your crankcase).

I still type too much. Not the first time I explained PCV but it's been a while, so it was fun! OP better have at least read it!! Also, I was too lazy to re-find and paste the article that goes into this (somewhere under the tech articles section, by a mamma's-boy-wiseman named something like Calan )

EDIT: Everything you ever wanted to know about the DSM PCV system:
http://www.dsmtuners.com/forums/articles-engine-fuel/366890-4g63t-pcv-system.html

 

[caseclipsegst]

I read the whole thing kenamond thanks for the info

 

[caseclipsegst]

Well today I did another boost leak and found the back side of the turbo housing leaking(16g).. Does this mean rebuild?

 

[my dreamt dsm]

I'm having the same problem. I think my rings are bad. I have a new mitsu pcv valve followed with a check valve but air is still getting in causing me to run hecka rich. But I'm also getting knock like crazy via evoscan.

 

[boost97gst]

If you had rings so bad they were letting enough air past to cause a noticeably rich condition on boost im not sure the thing would even run. Whats your comp numbers look like?

I'm having the same problem. I think my rings are bad. I have a new mitsu pcv valve followed with a check valve but air is still getting in causing me to run hecka rich. But I'm also getting knock like crazy via evoscan.

To OP:

The backside? meaning the turbine side? Or is it blowing through to your oil pan?
You have to remember that the turbo has no oil pressure on it so a little air leaking past the seals is normal. When normal oil pressure is running through the center housing it may not be leaking at all. How about running a BLT past the turbo. Like the next connection past it, if possible. How fast is the air escaping?
If its leaking really bad right out your hot side then there may be a problem. In/;out or side/side play?
Sorry for the numerous questions but it will help myself and others answer you more efficiently and accurately

 

[caseclipsegst]

The back side where the c clip is at... And it's not leaking horribly but enough to hear it.. Mind you the blt was done on a cold engine, my check valve and oem pcv have been orders but won't be here till next week but as of right now my only boost leaks are the housing,the first gasket on the tb, and the little adjusting screw on my Ngr bov.. My bov flange was leaking really bad but jb welded from the inside and outside and that sealed it up pretty good!

 

[boost97gst]

I wouldnt worry too much about it personally. Unless it was very excessive. Sounds like you're on you're way to a leak free ride dude. Awesome. Your leaks arent that bad at all and you will have them fixed easily.
Post up after the check valve is in and let us know if it fixes the problem you first described when on boost. Bet ya it will

 

[caseclipsegst]

Will do bro!! I'm a dsmer in a little town full of v8 owners so working on this car I've learned all my knowledge through this and other forums and I appreciate y'all helpin out