My 95 Civic LX automagic has dropped down to 23mpg. When i was doing long highway trips when i first got the car (@ 99k miles, now has 105k), i was averaging 28mpg. I was ok with 28, but 23 is pushin it

I have already replaced the PVC valve and fuel filter, and checked the plugs and wires. Should I go ahead an buy a new Denso O2 sensor? Is there any cheap way to confirm that it's the problem (no CEL) ? Would it be worth the effort to pick up an O2 sensor from a junkyard, or just drop the $60 on a new Denso unit? Also, is this a fairly easy job? I've read they get stuck pretty easily, so i'll be prepared with a good wrench + extension and some PB blaster.

Thanks!!

 

way back when i had a 97 lx auto, i never got more than 29mpg.... its the tranny i think

 

It could have something to do with O2 sensor. Also check for clogged cat conv. Run some Fuel Injector cleaner maybe? There are prob more things I am forgetting. I do remember a few threads on how to improve gas mileage recently... take a look for them and they prob will help give you ideas.

 

I did run fuel injector cleaner also on my last tank. How can I check for a clogged cat? My main issue is just whether or not to spend the $60 right away, or screw around trying to pinpoint the issue.

Thanks!

 

sounds like i have the same problem as you. the only thing i didnt do was new plugs, but i did fuel filter, plugs, new cap and rotor, fuel injector cleaner, pcv valve (but i used a cheap autozone one) thats all i can remember from the top of my head.

anyway i havent checked for a clogged cat (how do you check that) and im not sure about my O2 sensor either. i have no CEL's

it seems that if i drive it like a normal citizen most of the tank, or drive how i like to drive, being in vtec often i get the same mileage range about 25-26mpg

anyway im interested so SUBSCRIBED

to the solution to our problem

 

Does sound very similar, except that I've been driving like a granny to get 23mpg. I'd also like to know how to check for a clogged cat.

Do you have a 5spd or auto? Does anybody know at what rpm the auto should be shifting? At normal acceleration it's usually about 3100rpm for 1st -> 2nd.

Thanks

 

i think all cars are different when it comes to gas mileage cuz there are too many factors. i currently have a 99 SI, but before i this, i had a 95 LX 4 door auto, i used to get around 33mpg with it i believe, then the tranny went out on it and i was getting like 25.

im getting 25-26 on my SI and i know there are some people with SI's in the 30's and some that are turbo'd get better mpg than i do

 

What were signs that the tranny was going out?

 

On my 93 Lx, I was getting roughly the same or little lower than you. I was getting ready for my smog test again, so I did some maintainence which included: (just for my case of passing smog w/o going back multiple times)
- Changed cat conv. (Kragen $90, bolt-on too, no welding)
- Got another O2 sensor from junkyard (I got to choose the one I wanted, I chose the one that looked in better condition. Also I noticed changing the O2 fixed my idle problem.)
- Changed spark plugs, wires, and cap
- Oil change/flush
- Used carb cleaner in the manifold
- Cleaned air filter (Used the K&N charge kit)
- Bought that garaunteed to pass smog test injector cleaner at pepboys. (I forgot what brand, but it's the one everyone posts about on these boards)
- Re-tuned my timing ( I actually retarded it like 1-2 degrees)
- Made sure tire pressure was where it should be.

And I passed smog no problem, and I was back in the low 30's for mpg. I hope my experiences help you in getting better mpg back.


Modified by Sasebonian at 11:32 PM 10/13/2005

 

hmm well my dad brought it to this gas station cuz it was overheating. well the owner of the shop does good work, however the guy that worked on my car i had a bad feeling about (found out he's fired now) but i didnt think he knew what he was doing. anyway when i got it back, the car felt like it had no power. the guy that worked on my car prolly fucked around with it. but above 3,000 rpm's the rpm's would just soar and the mph would stay the same. a lot like a clutch slipping

 

maybe its winter driving? since you need to warm up, and theres more wind, rain or snow, that affects the mileage cause its more drag. i get about 40 mpg in summer and about 35 in winter on my dx.

 

They change gas formulations for winter climates (don't know if they already did it yet) so that can affect mileage.

Have you checked non-engine stuff? Alignment, dragging brakes, tire pressure and lead blocks in the trunk can do stuff to your mileage. Check and see if you have enough auto tranny fluid in there too.