Vacuum leak problem
 

Hi everyone. I’m having this vacuum leak problem that I can’t seem to shake. I did a smoke test and I have already changed the Disa valve, intake manifold gasket and the ccv valve. I also changed the gasket on the throttle body and the hoses going to the disa valve, and any hose that I could identify that may cause a problem. The vanos solenoids where checked and they are ok. What could be causing the suv to idle rough and the leak vacuum leak code to stay on? Any ideas or suggestions will be greatly appreciated. Thanks

Need some helpful info like which engine though disa means 3.0 and which exact codes you are getting and details like when does it come on? Instantly after reset, after second run cycle etc.


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Hi Andrewwynn:
Thanks for responding. The SUV has a 3.0l engine as you suspected. The code that I am getting is P0174 (system too lean -bank 2). I came upon the problem because the service engine light came on. I used my code scanner and got the P0174 code (vacuum leak). I smoked it and found smoke coming out of the disa valve so I replaced it along with throttle body gasket and intake manifold gasket. The code stayed on. I removed it and it came back on within minutes.

The most common cause of that code is the intake boot. The small part of the hose in the back will crack in the folds. Smoke is reverse pressure it could easily push the crack together. Basically the crack can act like a heart valve letting air in but not out.

You can spray carb cleaner near the area and watch the O2 sensor readings but just poke with your finger. Once you can no longer see part of your finger (because it's inside the boot) you've found the leak.

I had three invisible 1" wide tears in my intake boot by the time I got the same code.

No idea how it ends up on one bank maybe the IAC vents into bank 2.

Thanks Andrewwynn.
I checked the boot several times as this was said to be a common problem. It doesn’t have any leaks and there was no smoke coming from that area when I did the smoke test. However, just to be on the safe side I will replace it since it is not an expensive item.

There are a couple hoses connected to the boot. Cut the boot to get it off.

Also check the hose that goes from the ccv to the dipstick. Also a common problem. It's pretty buried and can be difficult to see smoke coming from it during a smoke test.

Shops use propane to find vacuum leaks. Monitor the O2 for rich indication.


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