I’ve got the “check engine” light on and it shows code 172 – fuel too rich. When I reset it, it comes back after a few miles (I think usually when the car idles for a while). Other than the annoying light and a little higher than normal gas mileage, there are no other symptoms. This is a 1.6 Protégé 99. Has anyone experienced this? Where to begin with troubleshooting?
Thanks for any hints!

 

You most probably have contaminated sensing wires in the Mass Air Flow sensor. Has been a huge problem for many years. Mazda has extended the warranty on this part for 1999-2000 Proteges with 1.6 engine for 7 years or 70,000 miles on non-California emission vehicle's. If you are still within that period and mileage then Mazda dealer will diagnose and replace free of charge.