Civic VX 26 MPG!!!

[nwrubicon]

Alright it won't let me upload a pic from my phone but the temp gauge needle gets to just below the temp symbol and holds steady

[slownugly]

plugged air filter? sounds silly but ive seen it throw rich codes on obd2. too much fuel not enough air.

did you reset the ecu after fixing the coolant wiring? i always pull the 7.5 amp fuse (in the underhood fuse block) for 10 seconds after making any changes or fixing somthing on my hondas. especially if the engine light was on.

[nwrubicon]

I'm actually running no air filter lol, I'm fully aware that that's a bad idea but it still wouldn't make it run really rich, and yes the ecu should've reset when I pulled it out and took the cover off to inspect it for things like broken solders or water damage, neither of which are present

[nwrubicon]

ok pretty sure my cat has gone bye bye. Correct me if I'm wrong but a cat has "honeycomb" shaped cells in it or a sort of lattice right? mine is completely hollow. I pulled the o2 sensor out and looked inside with a flashlight and all I see is a big empty cat, I can see the walls of the cat and the exit hole on the bottom, its not like its been hollowed out, the walls are completely smooth, it seems like its just completely depleted everything inside of it.

Also, I checked resistance on all 4 injectors and they all measure either 12.1 or 12.2 ohms. although they could potentially still be leaking

would not having any backpressure from the cat being hollow cause a false reading from the o2 sensor causing the ecu to dump more fuel?

[slownugly]

my cat has been gutted for 30k miles on mine and its returning 50 mpg.

however if it did come apart it might have gone into the exhaust and plugged it somewhere.

since there is no air filter is there any other modifications that are done to this car that are not brought to our attention?

[California98Civic]

Originally Posted by slownugly

since there is no air filter is there any other modifications that are done to this car that are not brought to our attention?

Ditto that. And would removing an airfilter from this car have any or all of these possible consequences? (1) increased airflow (2) colder air (3) changes in the MAP sensor readings (4) changes in AFR (5) increased pumping losses??? Couldn't this mod at least be part of the problem?

[nwrubicon]

alright so just filled up again and got 35mpg that tank, does anyone know if not having the white connector(shift light connector) plugged into the back of the gauge cluster does anything? because It wasn't plugged in until about half way through this tank and suddenly I'm getting almost 10mpg more...

[E.Roy]

Did you check the MAP sensor out?

[bikepilot]

I'd put that air filter back in asap. Only takes a tiny bit of dirt to trash the valves/valve seats and accelerate wear of the rings/bore. Running without one is an astoundingly bad idea (and probably hurting your mpg).

Did you replace the rotor with the cap? They wear together and should be replaced as a set. I also always replace the plug wires at the same time with OEM honda, which seem to be the best quality available.

FWIW in 220k miles the worst mpg our VX has ever done was 37 I think. That was just all city in hot weather with the AC cranking.

[BrickHouseVX]

OK HERE IS THE SOLUTION.!!!
My vx was getting max highway about 48, average about 43 hwy, and city was about 33mpg.

I did all the other things everyone else did and still no improvement until I did the following:

Check the fuel pressure like the honda service manual says. My testing found it to be below spec.
I replaced the fuel filter and the pressure went up a little on one test but was still low on the other test(having to do with the vacuum line on the fuel regulator).
The test said that I should test the regulator, and if that was working it was the Fuel pump that was the problem. Which was what I did.

I replaced the Fuel Pump and the two pressure tests passed!
It ran amazingly different, but still had a tiny "miss" it seemed like, which was reduce quite a bit from what it was doing.

I decided to replace the Fuel Pressure Regulator just to make sure. (ebay $15)
The MPG went up dramatically with these fixes.

But, it was still feeling like the motor was off a little. So I checked the timing and it was off quite a few degrees! Must be the new pump and stuff affected the way it was firing and timing.

After setting the timing it ran perfect! No "missing", no hesitation, lots of power, smoother, quicker, 70 and even 80MPG on the highway on certain straight stretches.

I drove from Lake Charles LA to Tallahassee Florida and with the MPGUINO calibrated I got 61 MPG going 55-63MPH. That was a tank average after about 474 miles. The fillup said I got 59.7MPG

So Recap;
New O2 Sensor(NTK), new ntk plugs or E3 plugs, new cap/rotor, distributor, wires, cat convertor never got it above the 48-52mpg average for hwy.

BUT
A new fuel pump and screen, fuel filter, and fuel regulator, then re-setting the timing to proper 16 Deg BTDC(?) fixed all the problems of:
poor fuel economy, poor acceleration, poor power, poor smooth idling when it got hot, poor morning starts requiring me to try starting the car twice before it fired.

I can not tell you how freaking awesome this car runs now! It really amazing. It runs like it was brand new.

Oh, also add MotorKote to the engine oil to reduce friction. This product is amazing. It makes the surface tension of the metal tighter thereby reducing friction. Other additives dont do this, except a product called Militec(?).

Key words: How to get better MPG from honda civic VX?
My vx MPG sucks.
My civic vx wont start the first time, but will the second time i try to start.
My civic vx is missing at highway speeds.
My civic vx is not getting good mileage mpg need to increase.
My civic vx has poor acceleration weak power poor idle wont idle good.

I hope this helps people. It took me a few years and no one on the forums had solutions for any VX owners with these problems that solved it. This one works!!

Let me know if it helps you.