all of a sudden bad gas milage
Thread Starter
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1st Gear
Joined: Oct 2008
Posts: 311
From: Morris, Illinois
all of a sudden bad gas milage
ok so i got my 1.8t about 2 months ago and i have been getting about 20-21 mpg. now im about half way into my tank and it says im averageing 18.5mpg im glad its doing it now that gas is $1.96 where i am and not the $4.40 it was when i got my car but does anyone know why this is happening btw i do have a code for my secondary air injection for incorrect flow that i havent fixed if that would do it or not?
Site Moderator
Joined: Sep 2005
Posts: 13,664
The secondary airflow fault isn't very important. You have a pump that shoots fresh air into the cylinder head on a cold start for emissions purposes. It shuts off after about 1 minute, if that. I'm guessing your car has ~100k on it for its age. If there are no other faults, start with replacing your plugs, air filter, and 02 sensor. Even if you dont have an 02 related fault, they get very lazy with age and are slow to correct A/F ratios and hurt mpg. Don't believe the mpg that your display shows either. Do the math old school style to be sure.
3rd Gear
Joined: Oct 2007
Posts: 2,158
From: CT
hah you said but plugs.
im not sure if you just said you did change your plugs or you were asking something, but as long as your MAF is new, change out the spark plugs and primary O2 sensor. the secondary one isnt necessary to change unless you have a CEL for it.
im not sure if you just said you did change your plugs or you were asking something, but as long as your MAF is new, change out the spark plugs and primary O2 sensor. the secondary one isnt necessary to change unless you have a CEL for it.
2nd Gear
Joined: Apr 2007
Posts: 1,161
From: Minnesota
If you live in the cold climate, your gas mileage isnt gonna be as good either, especially if you let your car idle for a while to warm up it was quite a bit warmer 2 months ago. Id hafta check the numbers but my gas mileage falls by at least 2 mpg when it gets cold id say.
Thread Starter
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1st Gear
Joined: Oct 2008
Posts: 311
From: Morris, Illinois
haha i ment what not but my bad. and i do have a CEL for the SAI should i fix it right away or is it not that important
Site Moderator
Joined: Sep 2005
Posts: 13,664
Hello? McFly? Anyone home? WTF I get your car towed all the way to your house and all you got for me is light beer?!