SO i went to an autoparts store yesterday and the guy tells me i need new spark plugs because my cylinders were misfiring. I bought new spark plugs today and installed all six of them them. I also filled up my gas tank to its fullest. So here's where i get really pissed. After i replaced the plugs and filled the tank which was around 3 o clock pm, i probably drove about 15-20 miles... by 2 in the morning, the needle in the gas guage was literally at its halfway point. Wtf?! And I'm not even exaggerating one bit. So i'm guessing there's something else wrong with the car. I'm planning on bringing the car to the shop to have it checked out. Anyone here know what the problem might be?? Seriously, i freakin hate paying $4/gallon.

 

How did you determine misfire? was that based codes you got from the car computer?
A code of multiple cylinder misfire is often 1 coil is dead, and fooling the sensors-
into saying its 3 or 4 of them. One coil cost about 50 bucks
Were any of the old plugs black and wet?- or were they grey to tan color and dry

What exact spark plugs did you install-??
the correct ones are just under 7 bucks each, the TL WONT run on 2 dollar plugs at all~ the special hi energy ignition fries regular plugs
Please answer the above questions for more diagnosis help

NGK Iridium IX used by many, its the upgraded version of the NGK Platinums that came in the car. Technology has advanced so you can get better than stock now

If you had CEL check engine light- you need to reset the ECU by pulling the clock fuse in passenger footwell- remove and reinsert- forces a computer reset/relearn
Just new plugs isnt likely to fix a misfire- so assuming coil prob- you will need to reset the ECU after each cylinder you try the new coil on- until it runs better! then you are done

Dont fill the gas tank to its fullest! If it warms up- like from the exhaust pipes or sun/daytime temps- it can actually push gas into the charcoal cannister emission control- which makes for other problems!!!~
Stop filling at the first auto shut off of the nozzle, that leaves the expansion room as designed into the system.


If you hate 4 bucks a gallon just wait a few months---- enough world and national events-weather, are happening to upset the oil supply again-
Just the threat of a disruption sends gas up 50 cents, what will happen when there is a real emergency?????????? 5 bucks a gallon will be a fond memory.
Some of us remember the original oil shortage in the 70s, when there was 10 gallon limit on purchase, and even -odd license plate- 3 days of the week you could even BUY gas!!! right here- in America!!!!

 

reading your post again: I see drove 20 miles after fillup - I am guessing it still read full when you parked, then at 2 am you went outside and started the car- it read 1/2 tank
IS that correct?

You MAY have a bad gas float level in the tank or guage, and its readings are off-
refill the tank, if it takes 1 gallon now- you used 20 miles worth of gas.
OR
You have a gas thief in the neighborhood- get a locking gas cap- that metal cover door is no match for a screwdriver~
OR
You have a serious gas leak- which you would smell from 10 feet away!
Lift hood and sniff around- same thing for gas tank
Check the rubber seal for the gas cap- no cracks or tears?

Some gas thieves are punching a hole in the tank- then slide a drain pan under the car and grab a few gallons.
Depending on where they made the hole, it could only leak out when above 1/2 full

 

What plugs did you get? Did you gap them? How did you determine that your misfire was sparkplugs? Most times out of 10 on our car a misfire is a coilpack.