ODB 1 trouble - check engine light on today

[johnj92131]

Took a long trip up to the high desert today (160 miles each way) to pick up a 4.2 long block.  On the way back home near Rainbow I noticed the "check engine" light come on.  It stayed on for the next 50 miles till I filled up the gas tank at Costco (22.65 gal and 400.1 miles).  When I restarted the car the light was gone and I made it home with out incident.

 

Just looked up this post in the DIY section:  Followed the procedure and I get a 51 code.  Most likely cause O2 sensor detects lean mixture check for vac. leak Now this was after 250 miles of 75-85 mph driving on a hot day.  So I will see if the problem happens again.

 

Now another small issue on the trip was the cold air stopped coming out the vents several times while I was trying to accelerate up a grade.  Is this normal?  Or am I loosing vacuum somewhere and the flapper valve moves to cut off the air flow?  As soon as I back off the throttle, the cold air flow returns to normal (till next time).

 

Taken together, do I have a vacuum leak I need to find?  What say you folks.

 

Thanks,

 

 

 

 

[HOrnbrod]

Check the plastic vacuum hose going to the reservoir behind the right side front bumper, especially where it passes through the front bulkhead near the battery.