So before I made a thread complaining about my 20mpg now i'm BARELY getting 15mpg driving very very conservatively and NO a/c. Of course a lot of things happened to my car in between my 20mpg and 15mpg. I think there was a sharp dropoff in mpg when i changed my sparkplugs from the original copper ones to ngk iridiums. My car felt a lot better after the iridiums went in though so I dont know. Any suggestions? could it be a clogged cat? or fuel filter? My car still pulls pretty hard so i dont think it's o2 or ks, but i'll check anyway. anything else i shoudl check?

cliffs -> 20mpg drops to 15mpg
possibilities
spark plugs? somehow changed incorrectly
old fuel filter?
clogged cat?
o2/ks?

 

im gettin around that, i average around 22mpg and thats about the best ive been able to get on my auto. check for codes, wouldnt be surrpised if the KS and 02 needed replacing.

 

i just went out and got 0505 which is all clear would my stuff need replacing even though it didnt trip a code?

 

Well check the obvious like the air filter and tire inflation. I found the cap of the positve battery cable conector in the bottom of my airbox....

 

i think my plugs were improperly gapped idle is stable so its not a vacuum leak air filter was changed with my plugs. I might change my fuel filter if i have time i'll do the plugs first. Whats the "proper way" to gap plugs? sorry i'm a noobie

 

grr my car runs smoothly so it shouudnlt be improperly gapped plugs. would an o2 sensor not working not throw a code at all?

 

if you have iridums you do not gap them, you will most likley break the electrode in the center. but if it is ngk it should be from .040 -.044 in which will run fine, and is where it needs to be. .044 +-.004

 

An o2 sensor can be working and seen by the ECU as being just fine when in fact the information it's giving the ECU is wrong.

If your car is "in tune" and your still getting poor gas mileage, change both front o2's even if the ECU isn't reporting errors.

 

okay thanks i'll change my fuel filter and both from o2s moeny money money

 

can i use bosch universal's or should i get bosch o.e. types?

 

mmmmm sound like KS

 

wouldnt my car feel sluggish if it were ks

 

10% ethanol?

 

Get the oem type so you don't have to bother splicing wires together.

Try the following too, if you haven't already:
- Clean throttle body
- Clean / replace air filter
- Replace fuel filter
- Replace PCV valve
- A bottle of Techron fuel injector cleaner
- Check your brakes - make sure calipers, pins, and ebrake cable are not stuck

 

do you think this is most likely my problem?

tire pressure is fine
engine runs smooth
air filter was changed
idle is fine
car still pulls hard

rawr everythign seems fine...

 

It's really hard to say.
I would try some of the cheaper alternatives I suggested first though.

 

uhm how would i make sure they're not stuck my car groans from a stop sometimes so that could be it too. I'll probably replace fuel filter + clean throttle body today what does the pcv valve do

 

PCV = Positive Crankcase Ventallation

http://www.misterfixit.com/pcvvalve.htm

 

probably not the knock sensor if its that bad, i had a knock sensor code for a long time and still was able to get 22-24 mpg

 

For the brakes:
- the caliper pistons should compress easily (front). turn easily (rears)
- the the grease on the caliper slider pins sometimes dry up and need to be cleaned and regreased. water sometimes gets in there too and causes them to rust.
- also dirt in the brake pad brackets can cause them to get stuck
- I'm not familiar with how to diagnose the ebrake, but I've heard it's been an issue with some people here.

If you're not familiar with the brakes, see if an org member nearby can come help one day. Check the regional forums.

The PCV valve is a little $5 plastic part from the dealer. Very easy to replace. I believe it diverts harmful gases from the crankcase back into the intake manifold to be burned in the engine.

 

I gapped my Densos, which have the finest elctrode tip on the market, and they were fine. You just have to be careful.

The NGKs I now have were cake.