Hello Folks, At 156K miles I got PO171, PO174 and Lexus code P1130 (bad air fuel sensor) I replaced the sensor and P1130 code is gone but the others remain. I have cleaned the MAF sensor and visually checked the vacuum lines, finding none loose cracked or disconnected. I checked the Vacuum at the take off on the intake manifold and it is reading 16 Hg, which is a bit low. I am suspecting a small vacuum leak or a bad vsv valve but I don't know how test for either of these. Or if you have any other ideas. Thanks ahead of time for any help you may have to offer. SB

 

I have always used carb cleaner sprayed in the area of the suspected leak (see if the idle speed changes) to test for vacuum leaks.

 

I have tried leak testing with propane but found no suspicious areas. While inspecting the vsv valves I tried removing the various vacuum hoses and blowing through them and found one on each that allows air to pass, I was reading on a forum that these are normally open valves so I think this is normal. Can anyone confirm this? Also down low on the passenger side below the radiator there is a cylindrical shaped can with a vsv valve on the bottom front for it and a vacuum line going into it. What is it? There are three vacuum lines coming from up above an one of them is blanked off, when I blow through that one I can hear air escaping from the above mentioned can. Any Ideas? Thanks SB

 

Low leaks are very hard to trace. Large ones and specially the ones near intake can be found out by spraying carb cleaner. Once I had a situation where the leak would spring up when the engine tilted as it torqued when stepping on gas.

If you know the plumbing, one can do sectional block and test. Shops can do smoke test.

It took me 6months to find a slow leak on sons bmw and it was around the canister and all it took was gas tank repair epoxy.

Good luck in tracing it. It might be worth your while to pay $$$ to get it traced and fixed.

Salim

 

Very common mistake, are you sure you cleaned the MAF correctly? Did you spray the long pin or the 2 hot wires? Your issue would be a dirty MAF sensor , a plugged fuel filter or fuel pump related.

 

GS4_Fiend was correct. I had cleaned the wrong part of the mass airflow sensor. Turned out that it was too bad to be cleaned and I had to replace it. Thank you again for your help. SB