Chasing some P0174 and P0171 codes and looking for possible vacuum leaks. My plan is to build one of the DIY smoke testers and pressurize the system to see if I can find anything.

In the mean time I'd like to ask the collective hear what and where are some of the more common points of failure that cause upper air leaks. A few that come to mind would be brake booster line, air injection lines, fuel injector o-rings and manifold gasket. Can you name any others.?

 

Just throwing it out there but it could be a MAF problem too.
Do a smoke test and/or 'carefully' spray carb cleaner around the vacuum lines and solenoids to find leaks.

 

You will find out with a good smoke tester
i also smoked tested the exhaust via the muffler
catalytic converters tend to leak causing o2 sensors codes
replace your purge valve as they will also throw o2 codes

 

If you're getting a lean code on both banks, it's not going to be a fuel injector. That would be too far downstream.

Pretty much any plastic or rubber hose back of the MAF will be suspect, including the joint between the MAF and the intake, which is supposed to have an O ring but often doesn't. There's also the PCV hoses, the IACV hose, and the throttle body gasket.

 

Plenty of vacuum hoses around the SAI, if you have that.

 

Check the 6 bolts holding the upper intake on. Sometimes they get loose & cause leaks.

 

Thanks for the feedback everyone. Im going to go down the check list and will report back what I find once I get a chance to work on it.

 

This is good news. I really was not looking forward to removing the whole upper manifold.

 

The upper intake is 6 bolts, and very quick and easy to remove.

 

Just following up with where I am with all of these codes.

After extensive searching for a upper air leak to no avail I came back to the forums and was doing more research. I read a post where someone said to disconnect my mass air flow sensor and see what happens. As soon as I removed the MAF connector the car immediately ran better and was no longer stumbling at idle. I cleared the codes and drove it for sometime and all seems well. No more P0174 and P0171 codes. After a restart I did get MAF related codes from it being unplugged. Im guessing that my 2 year old (BOSCH) MAF is failing. Ive already tried to clean it with no results. Ill have to buy a new one I guess or try and see how to test the current one.

In the mean time will I be OK to drive the car with the MAF disconnected? Will I do permanent damage? Seems to be running better than it has in a long time.