I decided it was time to replace spark plugs on my daughter's 2001 Tribute LX. All went fine in pulling the intake manifold and getting everything back together. The car started up and has runs well. However, after a few days the Check Engine light came on. The code indicates Bank 1 is running lean. A web search leads me to check the Mass Air Flow sensor and vacuum lines. I sprayed the MAS with contact cleaner, as instructed. All vacuum lines looked good. I sprayed car cleaner around the vacuum connections and manifold ports, but there was no change in idle. Doesn't appear to be any leaks.

Before I spend over $100 on a new MAF sensor, I'm checking if anyone has any other suggestions.

Thanks in advance.

 

The MAF services both bank 1 and bank 2. It would kick a code for lean bank 1 and bank 2 if it were the MAF. It knows no difference between banks.