Boost leaks gone. Now no more then 5psi. help

[winnipegguy2236]

Alright well my buddy is about to blow this thing up. After installing the boost gauge (knowing about boost leaks) the car would go strong up to 9psi. Brought it back in the garage today and changed the TB seals and fuel filter. Boost leak tested it to 20 psi with very little and slow leaking. Take it for a spin and she pulls hard and builds to 5psi with ease. Once she hits 5psi it stays there (no spiking) and the car holds the 5 psi to redline and that's it.
Only mods to the car is new O2 housing and full turbo back exhaust system on his 91 Talon TSI FWD.
Oh and also once you cold start it, it'll show 12 Vac until the idle settles to about 800 rpms and immediately the vac goes to 0 and idles a little rough.
Thanks everyone
P.S. you think putting in the MBC in would be a bad idea at this point?

 

[winnipegguy2236]

Anybody have some knowledge about this? Thank you

 

[ddavisaf]

You still have a boost leak, or a bad o2 sensor, or a bad coolant temp sensor, or a bad tps, or a bad isc, or a bad CAS.

With that said.... Check the turbo for shaft play.

 

[mitsuboy]

Also check for vac leaks.

 

[projctWraith]

Try all the above and then then also consider the age and condition of your gaskets around your turbo.( Exhaust manifold o2 housing etc...)

 

[winnipegguy2236]

You still have a boost leak, or a bad o2 sensor, or a bad coolant temp sensor, or a bad tps, or a bad isc, or a bad CAS.

With that said.... Check the turbo for shaft play.

O2 sensro is brand new, ISC is also new. What is CAS? the TPS might be bad because it did get water inside it. Anyone know if the MAF and maybe the tps would work from a none turbo 92? Any idea how much (length) i would need of vaccum line i should get in order to replace all the old lines. I'm taking the ones that all go to the throttle body.
Thanks
Would a boost test show vac leaks as well or is there a different proceedure?

 

[ddavisaf]

MAF would not work from a n/t. I'm not sure on the tps. I don't think so though.

CAS - http://members.shaw.ca/dsm.1000q/Engineprimer/1G/cas.htm

Vacuum leaks don't get checked with a boost leak test. Usually you can visually inspect them and you will see whether or not they're bad.
Vacuum hose is cheap, but I don't know how much you will need to replace all the lines.

 

[olmytsi]

I had this problem for the past month after dropping the 6 bolt in. Swapped throttle bodies, leak tested it, nothing. I said what the hell, ill disconnect the boost controller and see what happens...infinite boost
Turns out my manual boost controller just went bad sitting around in my trunk while i was swapping the motors

 

[ddavisaf]

When you do a boost leak test you're supposed to disconnect a boost controller btw.

Did you have a vacuum line connected to your wastegate olmytsi?

 

[olmytsi]

I dunno why ## asking that but my boost controller was hooked up the to the wastegate and boost source (the right way since it worked for the past 2 years).

When i couldnt figure out why my car was stuck at like 2-3 psi and i wasnt hearing my wastegate open, I went out one night, took the boost controller completely off the car...no source, no line to the wastegate and it boosted. So the problem was the boost controller. Got another the next day from a friend for free with no lines, hooked it up to my car with the same lines and the same exact way my old one was (to eliminate the fact that maybe a vacum hose was ripped and leaking), and its working today still

Its something to try and it takes 2 minutes...if that.

 

[ddavisaf]

went out one night, took the boost controller completely off the car...no source, no line to the wastegate and it boosted

I don't recommend this unless you're very careful.
You'll cause some damage if it gets away from you because it's telling the wastegate to stay closed and to never open. Pay attention to your psi if you try this method.

 

[olmytsi]

Obviously! This was done as a troubleshooting test and i didnt floor it til i got another boost controller the next day (having a fairly big turbo, it wasnt hard to stay out or on low boost).

 

[ddavisaf]

Obviously! This was done as a troubleshooting test and i didnt floor it til i got another boost controller the next day (having a fairly big turbo, it wasnt hard to stay out or on low boost).

Not critcizing you, just remember there are people that read these posts that may not know to stay off the pedal without the vacuum hooked up.

 

[winnipegguy2236]

Well i spent my night replacing all the vaccum hoses. Start it up. Starts idling at about 2k rpms and has a nice steady 14 hgs of vac. idle slowly drops as the car warms up (smooth feeling idle) as it continues to drop the Vac stays at 14 hgs. 1000rpms and still steady, at 900-800 rpms vac drop immediately and car starts to idle like crap. I'm ready to cry

 

[winnipegguy2236]

Would the idle suddenly act like this if the turbo wasn't spinning at idle?