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Old 01-27-2014, 02:04 AM   #1 (permalink)
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94 Civic VX California noob

Hi all,

I picked up a clean 1994 Honda Civic VX clean title first owner 188000 miles for a fair price.
No a/c but where I live I don't really need it, thanks to the ocean breeze of Pismo Beach. I have done a few research and did a few mods to the car since. The car is the Caifornia emission version.

- 44 psi on oem 13" tires
- car lowered 2 inches
- mud flaps are on....yea I know this won't help

First few tanks I was getting average of 38 mpg. I had check engine light of EGR insuffecient flow. I decided to clean the egr valve and cleaned the ports, still nothing changed. Still averaging the same mpg.

I later did a few tune ups with all oem parts, timing belt, water pump, spark plugs, oil change, trans fluid change. Did notice better idling and smoother throttle response but still same mpg. The best I had was 40mpg.

I bought a mpguino and converted it to Federal emission version with five wire oxygen sensor and ecu and wiring. I was averaging better at 45 mpg per tank. Best mpg was at 46.

Do note that most of the driving are at night and early mornings which averages at 55-60 degrees...not sure if this played a part in it getting less gas mileage. Oh and its a 80% hwy and 20% street driving. On the mpguino it will usually show an current mpg at 43-48 mpg when driving during night and morning. Then when driving during day time of 70-80 degree weather I see an average current mpg 48-54 on the mpguino.

I haven't try driving during the day to get an average on the tank but would colder weather play a big part in my mpg.?

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Old 01-27-2014, 08:37 AM   #2 (permalink)
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Originally Posted by greenVX View Post

I haven't try driving during the day to get an average on the tank but would colder weather play a big part in my mpg.?

Temperature definitely plays a part in fuel economy.

1. Make sure your thermostat is working correctly.
2. A grill block will aid in warm up and reduce drag created by air flow through the engine compartment.
3. Some have had success with warm air intakes

Diesel Dave finding's
40 deg F change results in about a 20% change in mileage. So mileage changes 1% for every 2 deg change. That's pretty significant.
From thread below

Use your search much Honda specific information on the site.

And remember to start a garage entry for you vehicle.

Last edited by nemo; 01-27-2014 at 08:52 AM..
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Old 02-04-2014, 12:45 PM   #3 (permalink)
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This is what I have done with good results so far.

My adjustable WAI / HAI build thread

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Old 02-10-2014, 08:56 PM   #4 (permalink)
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Thanks. I saw that thread, I will try something like that in the future.
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Old 02-10-2014, 09:12 PM   #5 (permalink)
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Old OE thermostats on Japanese cars will fail open. Before they fail they get lazy about getting up to operating temp. I think on the VX the gauge should read just below halfway, and it should get to that temp in less than two miles.

Idle speed should be 550 RPM.

Low operating temp will make the car run richer to compensate for colder temp. Before you buy the cheapest, check the OEM (read dealer but search the net for better price) and make sure the difference in price justifies the cost in mileage and possibly having to change the stat more than once.

Best ever mileage on my 94 was 68 MPG all highway at 60-64 MPH, 4.637 gallons of fuel for 300 miles. Many here did not believe it. The car was absolutely original everything, even tires made in 1993 and that mileage was from June 2008, on 15 year old tires. When I finally replaced them with Michelin X (on sale) myaverage MPG dropped by 7.

My 94 was a time capsule, bought it in March of 08, it had been totalled in 1995-6 then stored in an insurance training center for 15 years and used to train adjusters.

It had 27,492 miles on the odometer when I got it and it was original down to the wiper blades.

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Old 02-10-2014, 09:16 PM   #6 (permalink)
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Electrical drain from the heater and lights is part of it. this is especially true at lower rpms where the electrical load detector (ELD) commands full alternator power. A higher ELD signal to the ecu will also raise you idle speed.
The other is the slower time to get up to temp (especially if running the heater). Lean burn (LB) is engine temp limited in the lower gears (ie: too cold, won't LB).

Plus the whole minor difference in air density (air drag and pumping losses), but again, its minor.

Shooting for 600 miles of range at 65-70 mph out of a vx.

Last edited by Superfuelgero; 02-10-2014 at 09:28 PM..
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