I recently experience about a 15% drop in fuel economy. Because of a chain of events, I'm not sure what the problem is. Any suggestions would be appreciated.

1. Moved from Illinois to Texas ==> Lots more AC usage (Ran for 2 months without noticing drop in fuel economy.)
2. Cleaned EGR port. It was plugged. DTC P0401. I did not replace the EGR valve or install new kit, just cleaned it.
3. Scheduled oil change.
4. Replaced failed alternator.

All of the above happened at least 2 weeks ago and over the course of 2 months. I just noticed the drop this past week.


1999 EX V6, ~90K miles. No noticable driving issues.

Thanks.

 

Almost forgot.

5. Replace PCV valve (aftermarket part.)

 

may be time for a new O2 sensor(s)