The sensors that the computer chip relies upon (O2 sensor, MAS, etc.) can
age and cause declining gas mileage. Connecting a diagnostic test
inistrument to the car will read the fault codes to determine if an
emissions component has failed or is failing. You might also consider
changing the air filter if it's been awhile, even if it does look fine.
To avoid replacement of recent plugs and oil, ask the dealer to pull the
fault codes to see if an emissions component has failed. If it has, there's
The things that matter most are the air filter, front oxygen sensor, and the
mass airflow meter. If the oxygen sensor has over 50,000 miles, change it.
Also, an incorrect reading from a coolant temp sensor can cause a rich mixture.
These things can all be observed and compared to benchmark readings on a
425 White Horse Pike
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.