Bad Boost leak...HELP!!

skatershawn · Dec 13, 2009

I'll start with, my car drives fine unless im under boost.. under boost its just running super rich and fills like im only running 2 psi if that!!
no stalling, no funky idle!!

I did a boost leak test... OR Tried.. and it will not hold boost and i cant hear anywhere its would be letting out air!!

I try to fill it with air and sit there for a good min filling then pull it off to see where its leaking and i hear nothing.. so i get my pressure gauge and check to see if there is any pressure in the piping and nothing.. 0psi so i tried it again and filled it (or thought i was) and for a good min trying to fill then take it of and quickly check the pressure with the gauge and 0psi ZERO.... What could be leaking soooo bad but not miss my idle that much... my car drive Perfect unless i drive under boost??

PLEASE someone help!!

tunethis · Dec 13, 2009

I think if the valves are not it the right position, all the air will escape out of the exhaust. If this happens, just blip the starter and try again. The valves should sit in the right position to perform the test. As far as your low boost problem... when did this start to happen? Have you done anything to the car before this problem started? Make sure all your vac hoses are attached and not leaking and check all of your couplers and clamps too.

wondersb · Dec 13, 2009

Whenever I do a leak test I set my pressure regulator at the highest psi that the boost will be and have a quick coupler on the leak tester, so if there is a leak i have more time to find it. and if it is going threw the valves you will hear air coming out the exhaust or valve cover.

doubleclutch99 · Dec 13, 2009

When we do boost leak test on the diesels at my shop, we use soapy water to spray all couplers and piping connections. you'll know when you find a leak they bubble up pretty good.

skatershawn · Dec 14, 2009

i did that... and i ead the vfaq on how to do a boost leak test and says nothing about setting the vavles...

it simple just doesn't pressurize...

BUT i let my car idle lastnight i noticed a hissing noice as it idled... ive heard it before but i thought it was just cause the nipples on the TB had caps on them it was hissing through there... but i noticed it cause its been getting louder.. its actually pretty noticeable now... its either my intake manifold gasket or my injectors arent sitting right or something...
im thinking its my intake mani gasket because the fact that when i first got my engine back from the dude (he did the swap... well the engine) that rebuilt it i noticed a few bolts were loose in the back!! and i might not have found them all!!

Calan · Dec 14, 2009

Setting the motor to TDC (closing the valves) when you do the BLT ensures that air will not leak into the cylinders and past the rings. If you don't set it at TDC, you'll hear some air escaping from the VC or dipstick, but it shouldn't be much.

If you can't build any pressure at all, you have a pretty big leak somewhere. Start looking for couplers with holes or rips in them, and make sure they are tight (after checking that IM).

When you are out of boost and in open loop, the ECU will use the o2 sensor to keep the AFR around 14.7:1. Depending where the leak is and your intake configuration, you could be drawing in unmetered air but the ECU is masking the problem somewhat with the LTFT's. At WOT the ECU is just injecting the fuel it thinks you need based on the airflow, so you run pig rich.

skatershawn · Dec 14, 2009

ok.. well the vfaq thread didn't say anything about TDC... and how to i set it TDC without taking all my stuff apart and stuff?

i just get a wrench and turn the crankshaft pulley??

Calan · Dec 14, 2009

skatershawn said:
ok.. well the vfaq thread didn't say anything about TDC... and how to i set it TDC without taking all my stuff apart and stuff?

i just get a wrench and turn the crankshaft pulley??

You don't HAVE to put the motor at TDC for a BLT...but it definitely helps prevent leakage through the crankcase. Make sure the motor is warm also.

To put the motor at TDC, you can get close by just turning the crank with a socket (clockwise only!) until your cam gear marks are lined up and the dowels are straight up. The mark on your crank pulley (harmonic balancer) will also line up with the mark on the timing cover. Make sure the car is out of gear and put the parking brake on first though.

BTW - You also want to temporarily bypass the boost source going to the MBC if you have one, and may need to bypass the PCV valve as well, if it is leaking badly. Otherwise all your intake pressure is just bleeding out through the PCV valve and out the VC breather port, or through the bleeder hole in the MBC.

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Bad Boost leak...HELP!!

skatershawn

tunethis

wondersb

doubleclutch99

skatershawn

Calan

skatershawn

Calan

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