Contour Enthusiasts Group Archives Forums General Troubleshooting CEL code 1151 and vacuum leaks

This seems to be a popular topic here.
I have a CEL code 1151 -Upstream Oxyg Sensor lean thanks to the Codes from Common Problems Section
and read alot in this forum about vacuum leaks causing this CEL code.

I am suspecting a vacuum leak from the fitting at the top of the upper intake manifold, there is intermittent
hissing around one of the black elbows (EGR to Upper Intake Manifold line - at the manifold end).
Looks like the elbow is loose in the fitting, is that normal? how easy should the elbow slip out of the fitting?

Is there a way to verify a vacuum leak before working on the sensor?

Spray a small amount of carb cleaner at the suspected leak. The engine idle changes, youâ??ve found it.

jeff

The 1151 code is for bank 2. (front 3 cylinders) If you have a large vacuum leak from that far back on the intake you would typically be lean in both banks. It's always good to confirm any possible leaks, but your O2 sensor for that bank may also be fading, especially if you have over 60K miles on it.

Ok i'm sorry but i don't mean to cut in on ur post but i am having the same problems with my 95 se mtx. I am getting code 176 bank 2 running lean. I have sprayed tb cleaner around possible leak area's and nada. I suspect i also have a vaccum leak.

A few months back i did a motor swap and a few days back i have discovered there is a vaccum line pluged coming off the PCV valve and it does not connect to anything. I tried to check and see if there was something i can connect to but there was nothing? Could that be my problem. And by the way both o2 sensors are brand new less then 5 k on them. They are motorcraft. Please help thanks