How To: Recognize and repair a vacuum leak

jollib · **Joined:** Mon Jan 09, 2012 12:42 pm **Posts:** 10

Whats the parameter called on romraider? It actually measures the manifold pressure?

Also it should stay pressurized at 20PSI if im actually sending 20psi into the system am i correct and should stay pressurized unless I disconnect the compressor?

02rexwi · **Joined:** Wed Jul 16, 2008 7:32 pm **Posts:** 324

That all depends on the flow of your air source. Typically I leave the pressure regulator on my air line at around 90 psi so that I get maximum air volume, and shut off pressure when I see 20 psi. on the gauge. In Romraider you'll be looking for the parameter called "Manifold relative pressure- corrected*"
Once you get up to 20 psi shut off the air and see how long it takes the pressure to drop to 10 psi.
If it is sealed up well it should take 5 seconds or more.
It will depend a lot on where you are feeding pressure into when you do the test. The stock turbo inlet does not like to hold pressure very well, because it is not designed to see positive pressure. If you do pressurize the stock turbo inlet make sure you cap off the correct fittings on it.

jollib · **Joined:** Mon Jan 09, 2012 12:42 pm **Posts:** 10

my DYI pressure tester will only fit on the turbo inlet. which fittings should I cap off?

02rexwi · **Joined:** Wed Jul 16, 2008 7:32 pm **Posts:** 324

There are many writeups on boost leak testing WRX/STI's... I don't want to clutter up this thread any more with talking back and forth. This thread should help:
http://forums.nasioc.com/forums/showthr ... ?t=2205161
PM me if you need more information.

-Mark

dj-phoenixx · **Posted:** Mon Jun 25, 2012 3:27 pm

Hi,
a few days ago I had an closed Downpipe cat. I've removed them and now I think I've an boost or vacuum leak. Maybe it is an trouble in Exhaust. The AF Correction at idle is at 3,9% and If I run 2000 RPM it goes from -10% up to 9%. 4 weeks ago I've had an bad injector. In last year I've changed the two O2 Sensors.

Look my log. Maybe you guys have an idea.

Car Specs. USDM Legacy GT 05

Engine:
4 Zyl. Boxer Turbo EJ255
JDM SpecB Twinscroll Turbo (TD04HLA-19T)
Cosworth Headgasked
ARP Headscrews
EcuTek
K&N Panel Filter

Transmission:
EDM 6 Speed STi Gearbox with DCCD
EDM STi Diff R180
SpecB Propeller Shaft
EDM SpecB Drive Shaft front
Drive Shaft rear
HPI Clutch
STi Flywheel

Exhaust:
JDM SpecB Equal Length Header
JDM SpecB Up-/Downpipe
JDM SpecB Mid Muffler
EDM Prodrive End Muffler
Cutted Downpipe

Suspension:
Tein Flex Shock Absorber with EDFC
Cusco Stabilisatoren front and rear
Cusco H-Brace

Brakes:
STi 17‘‘ Brembo Brake Front and Rear
Dixel Brake Disk Front with Ferrodo DS 2500 Pad's
DBA Brake Disk Rear with STi Pink Pad's

Wheels:
Prodrive 8J18 ET51
Autec Zenit 7J17 ET40

Interieur:
2009 DVD Touchscreen Navi
JL Audio HD600/4 Amplifer
MB Quart QM 218.61 Q Speaker Front
MB Quart PVF 216 Speaker Rear
Blitz FATT DC Turbo Timer

Exterieur:
Black Mirror tinted Window
EDM Headlights
EDM Taillights

P.S. I'vnt make any Map changes yet after I've removed the cat in Downpipe.

Greets Marcel

02rexwi · **Joined:** Wed Jul 16, 2008 7:32 pm **Posts:** 324

Do a boost leak test. That simple.

dj-phoenixx · **Posted:** Tue Jun 26, 2012 1:00 pm

Hi,
I've doing it with my laptop and break caliper cleaner. No changes. After it I've cleaned my MAF and changed the front AFR Sensor with the old one. The only think is that the AF Correction make an higher amplitude.

Greets
Marcel

02rexwi · **Joined:** Wed Jul 16, 2008 7:32 pm **Posts:** 324

You should check out the link above, it describes how to do a boost leak test.

You must be doing something different if you're using brake cleaner. A boost leak test involves you pressurizing the intake system and checking for leaks.
Do it with a cold engine and spray everything down with soapy water and look for bubbles.

-Mark

dj-phoenixx · **Posted:** Tue Jun 26, 2012 3:09 pm

Soap water sounds interesting. I've do it only with break cleaner. If the engine runs out of any gear with 2000RPM or more you can hear how the AF corretion work. And If the engine goes back to idle you can hear light backfiring.
For info my AF Learning
1A is -0,70
1B is -0,70
1C is 0,00
1D is +10,5

IAM is 1

and no knock correction

Greets
Marcel

MikeCL · **Joined:** Fri Nov 07, 2014 8:31 pm **Posts:** 21

NSFW wrote:

What is a vacuum leak?

If you have the symptoms above, but you absolutely cannot find a vacuum leak, there next things to consider are in the tune:

* Injector latency too low - this will also cause a high AF Learning #1 A, with little or no impact on the cruising AF Learning (usually the "C" range).

* MAF scaling too low - bad MAF scaling can cause AF Learning values to range all over the place.

* Injector scaling too large - this can cause large AF Learning values, but typically (if the MAF scaling is good) it will cause all AF Learning values to increase together.

I think I'm having this issue here... it's bad enough I have some huge exhaust leaks around the DP and exhaust manifold but I checked all my hoses (did not try with propane yet) but I saw no disconnected hoses.. I have however been running without a front o2 sensor due to a issue with the last owner and a cross threaded bolt he stuck where the stock one goes.. I got a new RH header just waiting for the gaskets tomorrow.. I used to get -22-23inHg at idle now it's like -10 it has to be the injector I have it right now set to 1.5ms at 14V I'm guessing 1.8 might help..

RomRaider

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How To: Recognize and repair a vacuum leak

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