I just filled my CRX up and it only got 25 mpg. It's 100% stock besides header, test pipe, 2.5 inch cat back and intake. No CEL but does have a vicious idle, when I start it cold the car has a honda idle from 2000 rpm to 2200 rpm and when it warms up it idles from 1200 rpm to 1500 rpm. I cleaned out the IACV and did a coolant flush/fill and changed the air filter last night.

 

Fixing that idle issue will help. You could also do a tune up. When's the last time you changed your plugs, cap and rotor? How old is your o2 sensor?

 

x2 try this, my hatch gets around 30 and its not an hf and its not dual point either

 

Well I just messed with the idle screw and it calmly idles at 900 rpm'd now , and I am unaware on how old the cap, rotor and plugs are being that I got the car about a month ago, I was thinking of getting a fuel filter as well?

 

all good ideas fuel filter with todays crap gasoline i do one once a year

 

which idle adjusting screw are you talking about? The top one or the bottom one? the one on the bottom of the TB adjusts the base idle.

I had the same problem and my base idle was way off. You should not be idling that high when you start up. When I start up my hf in cold weather it goes up to about 1900 and almost immediately starts going down.

ohh maybe you are doing your math wrong. I have never heard of an hf getting that low of mileage. my hf routinely gets 45 in the city and one time on the freeway i got 64.1 mpg.

 

Your idle should be around 700rpms (off the top of my head).

Check your ignition and timing. Cleaning the fuel filters and fuel injectors is always a good thing!

Adjust your valve lash to HF spec.

If it's still bad do a compression test.

 

I adjusted the top one but it seems to be running fine, I've put 25 miles on it and it hasn't done that goofy idle once.

 

o2 sensor is my guess. i got low 30's when mine went. The engine light didn't come on right away either.

 

Would it cause the car to sputter occasionally?

 

I just filled it up last night and got 30 MPG, do you guys think it just might be too big of an exhaust?

 

well did you do a proper tune up yet? cap, rotor, spark plugs/wires, because sputtering can be missfire solution proper tune up.

 

Stuck thermometer can kill mileage too. sputtering can mean different things... does it do it consistently or randomly? Consistently is often a timing issue, randomly is often a distributor or electrical issue, like cap & rotor or plug wires.

 

Well I pulled the plug wires and cap off, and the wires are all corroded to hell as well as the cap. So I'm going to put a cap, rotor, plugs and wires and see if that helps(I'm sure it will.)

The thermostat seems to be working fine, It very randomly sputters, but isn't terrible.

 

I did a tune up(plugs, wires, cap and rotor) and changed the air filter. It's still getting 25 MPG. The O2 sensor has 10,000 miles on it. I have NEVER seen a check engine light.

EDIT: I just replaced the fuel filter.

 

does the check engine light work when you first turn on the key?? before you start the car? it may be a bad bulb. also check the LED on the ECU

 

Yeah it comes on when I key it up.

 

i thought i already posted this but perhaps you have too much of a flowing exhaust on the car? as in it has no back pressure so you're having to stomp on the gas to go any where?

 

After I did the tune up, the pedal feel has dramatically changed, now I just touch the pedal and it will scoot easily, Could it just be the exhaust? The cat-back is a glass pack to a 2.5 inch straight pipe.

 

I just filled up and got 36 MPG after the fuel filter change, I'm starting to think it's just the high flowing exhaust.