Engine acts like theres a vacuum leak, but no boost leaks?

[NightRider97]

I've had several threads over one ECMlink for a couple weeks asking about what could cause my issue but no one ever responds, if they do its something completely unrelated to my question or problem.
Like the title says I have an issue with my engine it started to become obvious about 2 weeks ago, barely stays running on a cold start if I try to give it gas it coughs out and dies. It can be seen in my logs as the wideband goes from full rich to full lean then dies. It just seems like an issue I've had before with a carburated engine that had a blown power valve that was leaking vacuum. Except according to my boost gauge at cold idle I'm seeing almost 25inhg vacuum. So I'm at a loss. I've done several boost leak tests and cant find a single leak so what would cause these symptoms and if its a vacuum leak as I thought, what would cause a vacuum leak that wouldn't cause a boost leak?

 

[96awd16g]

Vaccum leak is highly unlikely IMO. Typical vaccum at idle is 18-20, I've never heard of anyone seeing 25. If you had any leak at all I'd expect 16 or lower.

 

[Mitch41]

Was there absolutely no boost leaks? How long did it take to run down?

How is your spark? Have you checked it at the coil pack, and at the plugs?
Have you checked the plugs out?

Are you running rich on one cylinder? Is there moisture one one of the exhaust cylinders on your manifold when left running for a while? If you feel the injectors while the car is running can you feel all four firing the same?

And best of all... What all has changed since the car last ran properly?

 

[NightRider97]

This engine has never ran "properly" its always been a problem. I bought it from a professional DSM mechanic and it was not as it was sold to me as being. But I've done my best to make what I have work, until now, it just doesn't want to let me find whats causing this issue. I can't move on in my tuning with it running like this either.

On warm idle it will run at 15-16inhg, but cold idle its all the way up to 25inhg.

I suspected an ignition issue as well so I pulled the COP setup I had on it and installed the stock coil pack and some NGK wires, that did nothing for the problem at hand. So I had an extra ignitor laying around, so I installed that, did nothing for the issue at hand. Plugs honestly look clean when I pulled them.

As far as the boost leak testing, I have no intake stream leaks, at all. However if I open the valve cover all the boost leaks out in a matter of less than a second. I removed the PCV from the system after this and tested again, still get the same amount of air coming out of the valve cover. So I'm guessing I have rings not sealing anymore or possibly bad turbo seals, but this is a GT3076R so I don't know how its possible for that much to leak through one of those ball bearing turbos.

The guys on ecmlink have said to remove the PCV all together and plug the port on the intake manifold and run a catch can. I plan on doing this but I don't think its going to help.

 

[Colt4G63 also]

If you do a boost leak test pressure should not build up in the valve cover. Any pressure in there should flow out of the crankcase breather. If your boost leak test all leaks out in a matter of less than a second, I would call the test a fail.

 

[NightRider97]

Even if the only place its leaking out of is the valve cover? Basically if I don't plug the valve cover breather port it just constantly leaks out of there and if I shut the air source off its just gone in less than a second. If I plug the hole it will hold boost but as soon as I open the valve cover to atmosphere it all leaks out.

 

[Mitch41]

Mine takes over a minute to lose pressure from 15-20 psi, and that's with a beaten motor and a non-rebuilt turbo...

Something is wrong if you are getting that much pressure coming out the valve cover breather. Even when my PCV valve was toast (I could blow through it with my mouth), it still was a small leak.

 

[NightRider97]

Found what was causing this today, plus more.
The EGR blockoff plate appears to have warped and is leaking quite fast. I also discovered that when I boost leak test from the throttle body I get no sign of crank case pressure like I do when I test at the compressor housing of the turbo. So I'd say there's something wrong with that turbo.

 

[Mitch41]

"You will get some blowby in the crankcase while doing a boost leak test. Your turbo seals seal with oil pressure, so when your doing a boost leak test the air is escaping throught those seals and leaking through the oil return line up to your crankcase. You will also have some blowby through your rings."
Copied and pasted from a thread on the same issue on dsm talk.

Testing with the tester on the turbo is a much better method as it tests your hot pipes, intercooler, cold pipes, and blow off valve too.

 

[Colt4G63 also]

Some will leak past the turbo seals during a BLT, but it shouldn't lose all the air instantly. Sounds like the blockoff plate was the real problem maybe. If the car doesn't smoke, I would say the turbo seals are probably ok.

 

[NightRider97]

No I've been told for some time that it smokes blue on acceleration. But I always thought my blue smoke and crank case pressure issues were from bad rings in the engine, but my compression test came up perfect so I'm back to thinking for some reason the turbo seals are not sealing.