About 3 tanks of gas ago i noticed a major drop in fuel economy. i ust to get just under 20 on the hwy and about 15.5 in town.

Averaged out for the last 2 tanks i get about 14.5 on the hwy and 11 in town.

Any ideas guys?

The last mod i did was the TB bypass about a month and a half ago.

 

Clean your air filter lately? Change oil?

 

Cleaned my K&N about 5000 miles ago. Oil cahnge every 1500- 2500 miles.

 

Check for an Over oiled K&N filter. The oil could have formed a residue on the mass airflow sensor. If you suspect this, get some electronics cleaner and spray the sensors clean.

 

I kinda ignored cleaning the MAF for the longest while and when i finally did it made a big difference, especially since i had a habit of overoiling my K&N...

 

I checked there is no oil residue on it.

 

Clean it anyway. I use rubbing alcohol and a cotton swab. Also, you might think about getting new upstream O2 sensors as they directly effect mileage when they start to go bad or get dirty.

 

cotton swab? do u actually touch the sensors on the MAF? i'm kind of in the same possition and i've sprayed mine with electric cleaner though now i'm questioning if i cleaned it good enough.

 

Yes, but make sure you don't leave a single strand of cotton fiber or it will burn on the hot wire. Mine got some baked on oil on it and mileage went from 15 around town average down to 12. Cleaned the MAF and it's back to where it should be.

 

so just some elecrical cleaner? and maybe check the upstream o2s? how would i check them? just replace them or is there a way?