About a week ago I changed my oil and did a sea foam treatment with the car at 50k miles. I did all 3 steps of sea foam, but I dont think I did the intake procedure correctly. I slurpped in 1/3 bottle, let it sit for 5-10 minutes, then did about 4 0-60 pulls. My gas mileage went from 25mpg city to 15mpg. If I did not burn out the sea foam would that cause a huge buildup inside killing the gas mileage? I even did the intake again and really made sure to burn it, reving at idle, lots of runs.

I read to change spark plugs and did those today. NGK's. Idle is so much smoother but gas mileage still crap.

I did change oil weight from 5-20 to 5-30. Would that cause that big of a difference? Im stumped. And it didnt happen until i did those two things so i know its not the gas mixture or tire pressure.

Could I have clogged the fuel filter? Thanks ahead of time. You guys rock

 

Maybe your injectors are still dirty. hope ur pumping Shell or Chevron, none of the cheap gas. And when u say 0-60, do u do that with half throttle or full throttle? Make sure u full throttle past 5k rpm when test driving.

seafoaming a TL
http://www.youtube.com/watch?v=gAH3Q0vNZro

 

thanks for the reply. I did do full throttle, past 5 k rpms. repeated all sea foam again. replaced spark plugs (thought it wouldnt hurt at 52k miles anyways) car idles starts and runs smoother but gas seems to only be affected when im driving in the city or uphill. Literally 12-13mpg. But highway is still around 30mpg.

Anybody think o2 sensor? Or do I need to wait for a code? My other question is maybe the fuel filter. Is there a test to check the flow of fuel etc?

 

have you checked your air filter? hows your alignment? shouldnt be an o2 sensor if there's no check engine light. also try resetting your ECU. search on the forum how to do that. it literally takes 5 minutes