new to me 92 Civic VX mpg ?'s/mods

[coletrain777]

Hey all,
I just purchased a 92 Civic VX and I really like the way it drives. The car has it's problems (some rust and wear), but seems to be a great driver. The only real problem is that it needs a new o2 sensor (stock one caused dead pedal at steady cruising speed, had to mash the accelerator to get it to rev again). So to get it to drive normally I simply unplugged the o2 sensor and it drives great.

I drove it 200 miles over the weekend and got 38 mpg (mostly hwy at around 70mph, but probably 25-30 tough stop and go miles as well), which I didn't think was too bad. Tires are currently aired up to 58 psi. Also, I live in rural Missouri where it is physically impossible to obtain gas without 10% ethanol, and they are trying to pass legislation to increase that number to 15%. I simply say this because ethanol supposedly has and adverse effect on mpg.

Now that everyone is up to date on the details, I have a few questions:

1. If I drive sensibly but still maintain 65-70 mph on the highway, and I don't EOC or P&G, what type of mileage would you expect to see from this car with a functioning o2 sensor?

2. What other mod's (mechanical mods) are proven helpers for both mpg and performance?

3. Any other tips or tricks about this car?

Thanks in advance for the replies, it's nice to be a part of such a knowledgeable and helpful community.

Cole

[coletrain777]

Nobody???
I promise that I searched before asking any questions... does that help?

I know several of you have these cars and are possess a wealth of knowledge about them, any tips are appreciated.

Do I need to know the secret handshake ?

[Daox]

The "dead pedal" you describe is called lean burn mode. Its what makes your car more efficient than most. Reconnect the O2 sensor and learn to try and keep it in that mode. You'll get way better mileage that way. I'd expect mid 40s from the car.

Other than that, I'd do a grill block and warm air intake. Or, just look at our 100+ mods list.

[Ryland]

Depending on how bad it is, that dead pedal feel could be lean burn but I would say it's the o2 sensor and without the o2 sensor your engine is in limp mode running on a safe default setting, not getting good mileage.
as for other mods to make? I'm a big fan of the stock drive train, with sythetic oils, be sure to change you tranny fluid as it should be done every other year and is a good chance it's been 10 years, good motor oil is all it needs.
Keep your exhaust stock and your engine will run best, I've pulled some weird exhaust systems off my vx's and always saw an improvement, if mufflers rust out quickly for you then go to a honda dealer for the parts, install them your self, not much higher price the an auto part store, they fit perfect and they have a warranty for as long as you own it.

[coletrain777]

Thanks for the replies guys,

Daox - I don't think the dead pedal is lean burn mode, it will immediately go into this when I ease off of the throttle, but takes 2-3 seconds of mashing the pedal to the floor to get the engine to react at all (no revs). This is a big deal when just trying to get up my driveway (1/10 of a mile uphill), because unless I am giving it hard throttle it will go into this "dead pedal" mode and almost come to a stop. If this is normal for lean burn let me know, but I can't believe Honda would devise a system like this, it would be very dangerous for the average driver.

Ryland - Yes when I unplug the O2 sensor it runs perfectly normal. I know that I need to get one back in there, but man are the HIGH priced. I have read the reviews about the aftermarket ones, but the reviews seem mixed about how well they work. I will be keeping the stock exhaust and also will be switching over to good quality (low friction) oil in the engine and drivetrain.



Not to start controversy, but does anyone have a suggestion on the best place to purchase my 02 sensor. I would love to hear your experience with aftermarket sensors or otherwise.

[comptiger5000]

For most cars, the safest bet is an O2 sensor from the dealer. I know Jeeps in particular do weird stuff with aftermarket sensors.

[tim3058]

I was gonna replace the O2 in my DX/VX, I had sticker shock at the local Advance Auto ($340 if i remember right). A couple folks on here said go with a cheapo ebay O2, and replace it if need be in a few years. I paid $60 or $70 for one on ebay and its been working fine for me. I've for the most part, had good luck buying civic parts on ebay.

I've got a few mods, and have really tried to tailor my driving style to maximize mpgs... am around 54 mpg this tank (no EOC, and just starting to try P&G via engine-brake). I'd say for mods:

1) vacuum gauge (a must-have to keep the engine in lean-burn)
2) mpguino (well worth the $55, dcb on here sells 'em)
3) grill block (havent done it yet myself but everyone has good luck with them)

The biggest mod is your driving style. Keep it in lean-burn and you will improve mpg's fast. Try to avoid braking and use engine-brake downshifting to slow down til 2nd gear (then brake)... really helps mpg. I know this will probably get shouted down but (ahem) adjusting your driving location to (ahem) favor the low-pressure wake of a larger vehicle really boosts my 65mph mpg (even at a relatively safe distance)

[user removed]

Mine is a time capsule with just over 54,000 actual miles. I bought it salvage with 27,492miles in March 2008. Original tires.

My best tank was 68 MPG in the summer of 08 at 64 MPH drafting 3 stripes (about 130 feet) behind big rigs on I95. 300 miles on 4.6 gallons of gas. Traffic on that road is so heavy, I still had cars pulling in front of me in the right lane and passing other cars on the right in the distance between me and the truck in front of me!

When I replaced the original tires my mileage dropped drastically, but the original 15 year old tires were dry rotted and I did not want to risk a blow out and body damage.

The worst mileage I ever got was 46 at 70-75 MPH on I64 east of Richmond.

Lean burn is easy to feel in my car and it pulls fine from 1000 RPM at 30 MPH in 5th gear.
60 MPH is 2000 RPM. If these speeds and RPMs don't match your car then the transmission has been changed and your mileage will suffer.

The difference in performance in your car with the sensor plugged and unplugged indicates you have other problems. One I would suspect is the EGR is not functioning properly.

What to do?

It could be a long list.

Check compression
Timing, both cam and distributor
Check to see if the car is easy to push. I can push mine with one thumb!
Are your wheels like the ones in my photo, they were special.
Tires can make a huge difference in mileage.
Check fuel pressure.

If you are worried about the cost of an 02 sensor then your budget will mean you need to do the work yourself, and you may need to buy tools to do the work.

I included a photo of my engine compartment. If yours has different induction parts or other different parts then it has been modified and that could cost you mileage.

My last two tanks were 54 MPG at 65 MPH and 57 MPG locally.

I drive very conservatively and seldom go over 50 MPH on the local route. I use P&G and DFCO extensively, but no engine off coasting.

Tires on my car are Michelin X and are inflated to 44 PSI (sidewall max).

My car still has the original 02 sensor, original fan belts, brakes. I had the timing belt replaced, spark plugs, air filter, and wiper blades. Almost everything else is original except the tires.

My driving is focused exclusively on mileage and I have lived in eastern Virginia most of my 59 years. I do not have to deal with rush hour traffic.

My mod are WAI and a partial radiator block in winter.

This summer I should see some tanks over 60 MPG, the tires have worn in to the point where they are not as big a mileage hit as they were when they were first replaced.

At 54,986 miles I have driven this car as far as it went before it was hit in the rear end and totalled sometime around 1996. After it was totalled it was stored inside and used by the insurance company to train adjuster for 13 years, which is why things like the original tires and fan belts were in such good condition when I got it.

The roof still has the original paint!

regards
Mech

[coletrain777]

OK,
So here's where we are at so far.

My car is a totally stock 92 civic vx:
stock wheels
175/70/13 tires (will probably go back to original size when needed)
all stock engine and exhaust
new air filter
new plugs (although they are autolite... should I switch to ngk zfr4f-11)

I just went out an cleaned the egr (it looked pretty good), and then took it for another drive... no change.

Here's what I believe is happening; the dead feel is the car entering lean burn, but the problem is that it has NO power once it kicks in. When I say it has no power I mean NO power. It will not keep speed or accelerate even downhill (small grade not mountain) unless I blip the throttle to kick it out of lean burn. So my question is what would cause it to act like this when in lean burn? I am sure it should probably be able to hold speed on a totally flat road at medium speed (50-70 mph).

Car seems to idle fine, drives great either with the o2 sensor unplugged or with enough throttle to keep it out of lean burn. The only thing that needs immediate attention is the exhaust has a leak in the middle of the pipe (2 feet before the cat), could this small lack of backpressure cause the condition I am describing?

1. Do I need to change the plugs immediately?
2. Does it sound like an o2 sensor problem?
3. Could the exhaust be causing the problem?
4. Any other ideas???

I am getting ready to start traveling for work in a few days and would like to have this somewhat ironed out by the time I do (so I can start getting those mid 40+ mpg's).

[tim3058]

Random thought: could the tps or ignition timing be at fault? a vacuum leak? I kinda doubt the exhaust leak is to blame for something like that, unless the pipe is falling off. Have you checked the voltage at the O2? Til you check the O2 it could be anything, just that by unplugging the O2 you are bypassing the whole closed loop system, wherever the issue may be. Do you get a Check Engine light, or any codes?