Nebraska
(Member)
09/06/17 10:02 PM
Boost leak test results

Did a boost leak test and noticed all the air from the test was coming out of the valve cover.

In addition the car idles fine, drives fine until boost. Seems to lean out and misfire terribly. When I say misfire, it feels like I'm entering boost and then all power is lost. Thing stutters hard all over itself like (who would've guessed) a huge boost leak!

Compression results yield about 120 psi on all 4. Service limit is 121 I believe so I know I'm cutting it close but at the same time I'm not burning oil and a drop of oil never helped my test so maybe my rings aren't bad. Engine has 155k on it.

This leads me to the head. I have yet to do a leakdown although I suspect guides and seals could be bad, guides in particular. Car Does not smoke. Also I plan on looking at mechanical timing of the 4g as it could have possibly slipped a couple teeth. Anyone experienced a slipped belt?

Any insight would be very helpful, may try new plugs and wires just to see as hopeless as it sounds. Something is not right, I Could log but no
CEL. I'm a confused.


transparentdsm
(I have to say something dumb Member)
09/07/17 08:14 AM
Re: Boost leak test results

check your PCV

Nebraska
(Member)
09/07/17 11:04 AM
Re: Boost leak test results

Pcv and injector seals are the first boost leaks I fixed on this car.

transparentdsm
(I have to say something dumb Member)
09/07/17 03:43 PM
Re: Boost leak test results

if it wasn't an OEM one, pull it out and check. i have had brand new ones leak from the local auto store. it takes 5 minutes to check and its the only port i can think of that goes back into the engine. if it is leaking, just add a 1 way check valve that has a PSi that coincides with your boost levels.

edit: im sure if i looked through my bins i probably have 1 or 2 brand new aftermarket ones that are leaking.


Nebraska
(Member)
09/07/17 04:36 PM
Re: Boost leak test results

Funny you mention that...bought an autozone one; failed. Bought OEM; failed. Now I'm rocking the RTM plastic check valve.

Has anyone experienced boost bleeding out the valve cover?


transparentdsm
(I have to say something dumb Member)
09/07/17 04:52 PM
Re: Boost leak test results

well shit, you got all those bases covered then. last thing i can think of before you start to get into serious parts is valve stem seals.

Nebraska
(Member)
09/07/17 07:25 PM
Re: Boost leak test results

Hey I try man(:

Are seals a real possibility? I know I mentioned them in my first post but I'm unsure of the symtoms.


mooserage
(New Title)
09/07/17 09:12 PM
Re: Boost leak test results

For me, bad valve stem seals are evident when I pull vacuum for a decent amount of time (like 30-60+ seconds) idling and taking off I can see a small cloud of blue smoke (oil) that got pulled in past the seals during vacuum and burned up. It won't burn oil otherwise in my case, but specifically after idling it will. Now, that may just be the extreme end of the worn seal spectrum too, not saying its the only way to know you have bad stem seals. But, if you have had that, then it might also point to the stem seals.

kumfasa
(Member)
09/09/17 04:19 AM
Re: Boost leak test results

You said " all the air" are you sure its all the air.
When I boost leak test I get some coming from the breather hose from the valve cover. This is whatever gets past any open valves and the rings. (I dont bother to put the car at TDC cyl 1) I normally jst clamp this hose so I can hear actual boost leaks.

Your low compression numbers would likely mean that more air is getting past you rings into the crankcase and then out of the valve cover.

Try setting the car at TDC Cyl 1 (I believe all intake valves should be closed at that position.) This will limit the air getting to the cylinders and past the rings.


Nebraska
(Member)
09/09/17 08:19 PM
Re: Boost leak test results

I generally clamp that hose as well.
I will look at it some more tomorrow and get back here with some info.



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