172 O2 sensor lean code

[jballard81]

Replaced my fuel injectors and many of the old vacuum hoses recently.
Afterwards I'm getting code 172 which is indicative of a vacuum leak. (I just replaced both O2 sensors)

With engine on I went around and sprayed all my hoses and where the intake meets with carb cleaner and didn't hear any engine changes.

Kept digging around where I was working and found that this tiny plastic hard line was broken

That T leads over to the air box so that could account for the leak (maybe?).

I'm going to cap the T for now, but what is that little reservoir looking thing on top of the AC box? I need to know what it does so that I can prioritize it's replacement

As always, thanks!

 

[jballard81]

So capped off that T and went for a ride. Check engine light came on again, after about 5ish minutes of drive time, same code.

In terms of trouble shooting, I have a vacuum gauge I believe. I've never used it before but it makes sense to me to figure that out and if it's within the correct range maybe that means my O2 sensor already went bad?

 

[jballard81]

Found this thread with a similar sounding issue:

Questions on fuel pressure and smoke test results. Need help figuring out OBD-1 code 172 on 94 Mazda B4000.

94 Mazda B4000, truck started throwing a 172 code (lean passenger side bank) I haven't been able to get rid of yet. Code does not pop up until I have been driving for awhile which seems consistent for this type of lean code. What I have tried: 1.) Sprayed around engine with carb cleaner...

www.therangerstation.com

I can check the intake and exhaust torq. Ultimately I can redo the intake work and check everything again. Would prefer to not do that if possible.

 

[jballard81]

Went through all the vacuum hoses again, no real changes but drove it again and didn't get a code. Went for a longer drive and it through a code for just a second and then went away.

Maybe the gasket is settling in or the PCM is relearning or who knows but it seems the code is going away.

 

[SenorNoob]

I have the same intermittent code. I highly suspect mine is from an exhaust leak at the flange to the catalytic converter. It only happens when I idle or drive with low rpm for several minutes. I didn't have problems until I cut one of the bolts out of that flange.

 

[jballard81]

I have the same intermittent code. I highly suspect mine is from an exhaust leak at the flange to the catalytic converter. It only happens when I idle or drive with low rpm for several minutes. I didn't have problems until I cut one of the bolts out of that flange.

I'm going to rig up a smoke tester today I think. I haven't messed with the exhaust of this truck at all, but i wouldn't be surprised given the neglected state that I found it that it could have an exhaust leak