rice is nice

So my 98 civic is getting horrible gas mileage. I had a cat efficiency code about a month ago, but after having it for a week it went away.

I'm thinking either I have a bad or multiple bad injectors, bad front or rear o2 or bad cat.

I don't want to replace the cat unless that's the problem, i've heard that a bad o2 can give a false cat code. How do I test each of these things without just buying parts and throwing money at it?

russlan44

take ur cat out and look at it, i burned my cat in one week cuz my o2 sensor was bad. also i could be spark plugs, wires, distrubitor cap, gas cap, o2 sensor

Former User

Do you also have low power? If so, the cat might be clogged.

Otherwise, also check the spark timing with a timing gun and whether the PCV valve is working.

rice is nice

How do I check the pcv?

Guess I never thought of the spark, Probably wouldn't hurt to change the cap, rotor, plugs, wires. It does have 187,000 on it.

And no, it doesn't appear to have low power, pulls pretty good.

what mileage should a ek ex sedan be getting? Also, there are a few small holes in the muffler, can this contribute to bad mileage, or does that have no effect cuz its post cat and o2?

OH, this is a manual by the way, and it doesn't matter if I beat on it or drive it like a grandma, gets 23mpg city.


Modified by rice is nice at 11:03 PM 7/9/2008

Former User

Clean the PCV valve off. You should be able to blow air freely through it in one direction (to IM) but not all in the other direction.

Yeah, a basic tune up won't hurt, but also check the ignition timing.

The holes in the muffler should not cause a problem unless debris is restricting exhaust flow.

My 97 D16Y7 5-speed gets about 30 mpg from a mix of freeway and city (mostly) driving.

Any CEL codes?


Modified by RonJ@HT at 12:41 AM 7/10/2008

p10hlm

be sure to use all oem parts when doing the tune up

rice is nice

Nope no CELs.

Vindicator9000

Don't know about a sedan, but when I still had a d16y8, my EX coupe consistently got 36-38 combined mpg, often 41-42 highway depending on how I drove it.

IMO there's something wrong with your car. Without a CEL, it could be a lot of things... my vote's O2 sensor, but I'm just guessing.

98_EX_sleeper

im having the same exact problem with my EK coupe but i have a bad IACV and a crapped out knock sensor im getting maybe 15 miles to the gallon

EL Vap133

Maintenance is key, if you don't keep your car up to par it will do that especially with higher mileage.

rpared01

DAM! you getting really bad mpg's. a tune up never hurts. i would just replace o2 and the cat. My h22 gets me a 22-26 mpg of mix city and highway

rice is nice

****, i'm gunna try the o2's and the injectors, also take out my cat and see what that looks like, see if that cures it.