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Old 05-12-2009, 02:42 AM   #1 (permalink)
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Sipper - '98 Honda Civic HX
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California HX owner

Hi guys/girls I just purchased an HX 5 speed and wanted to introduce myself.

I commute about 70miles/day to work and needed something other than my truck to get me around. It was either a TDi (the reliability issues turned me off) or the HX. Both were hard to find in 5 spd but finally found one that was stock!

I pulled the scangauge from my truck, installed it on the HX and adjusted the motor displacement. On the freeway im driving about 60-65mph no traffic. My last half tank I drove 65% freeway/35% city with AC on 80% of the time (I couldn't wait to see my MPG!) and got a disappointing 32mpg. I also recently smogged it and it was running rich according to the smog tech. It passed, but it was a few points below failing.

According to the service records, part number 36531-P2M-A02 was replace in late 06, I am assuming this is the 02 sensor.

Im wondering,

Do I have an expensive 02 thats about to die? That will totally kill the $$$ savings of finding an HX. The scangauge says at 60-65mph w/ 15-18 TPS gets me 45-60mpg.

Maybe Im jumping to conclusions but I will post an update when I'm finished with tank #2 which will be 80%-90% highway

Looking forward to learning/contributing!

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Old 05-12-2009, 09:50 AM   #2 (permalink)
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Welcome to the site.

I can't help you with your HX problem, but I am looking forward to seeing what kind of mileage you get out of it. The HX is a great car.
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Old 05-12-2009, 10:07 AM   #3 (permalink)
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Honduh Power - '98 Honda Civic HX
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98 hx?? ..... frriennnd ..........

Welcome!

We have the same car! Even a CA spec too!
Unfortunately, getting good mileage means sacrificing things AC, which hurts your fuel efficiency.

As far as the 02 sensors go, I know that there are two of them on our cars. One is not too painful to replace, the other one is really expensive. But I could be mistaken. My advice is don't spend money to fix something that you are not sure is broken. Not passing smog can come from a lot of different things.

I don't know how many miles your car has, but I just got mine 8 months ago or so with 170k miles, and first things first, I ran "sea foam" through the engine which really help clear out a lot of buildup in the engine. I also changed the spark plugs and spark plug wires and that right there I KNOW helped out with the engine running smoothly and low end power.

I got performance 8.5mm plug wires, even though they were a bit pricey (80 bucks) but the new ones measured about 100 ohms and the old crappy ones on the car measured 10,000 ohms. Not exaggerating. So that maybe something like that will help you too.

... And another thing, our cars have "lean burn mode" that I do not believe the scan gauge will normally pick up on, but I think it sounds like there are ways to set it up to read it more accurately.

Welcome and happy modding!
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Old 05-12-2009, 11:46 AM   #4 (permalink)
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Cool, looks like there are quite a few people with the HX. I love it so far. I have not been using AC and I try to keep between 50-60 mph on the highway. 50 if I'm on a 55 speed limit road and no one behind me, 60 if I'm on a 65 speed limit road and no one behind me or its two lane. I can feel the lean burn quite a bit and can keep it in there really well if I stay around 52mph. Is it true you don't have lean burn on the CA model? Good luck with your HX.
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Old 05-12-2009, 02:34 PM   #5 (permalink)
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Welcome to ecomodder! I thought your highway mpg sounds good, but it's hard to be sure. You could monitor the o2 sensor with the SGII and see.
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Old 05-12-2009, 02:57 PM   #6 (permalink)
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Originally Posted by SVOboy View Post
Welcome to ecomodder! I thought your highway mpg sounds good, but it's hard to be sure. You could monitor the o2 sensor with the SGII and see.
You mean with an X-Gauge? If the HX is injecting more fuel because of a bad 02 sensor, then the SGII might not "see" this because it doesn't use the 02 sensor in it's MPG formula. At least that is what we have speculated in other threads.

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Old 05-12-2009, 11:44 PM   #7 (permalink)
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Its my understanding that the only significant difference on the CA spec vs regular hx's is the ecu. I have an L33 or whatever ecu whereas you probably have an A31 or A33. I believe the main reason for this is because of emissions, the lean burn mode supposedly creates a lot of noxious gases and I think I read somewhere that someone experienced their california hx leaving lean burn mode now and then to "burn out" the nox gases.

Like stated above, you will get a feel for keeping it in lean burn mode. I have no instrumentation or indicator for lean burn mode, so it is difficult sometimes, but basically anytime I feel a little boost in the power of the engine while I am cruising, it means that the engine has kicked out of lean burn mode (I think) and by reflex I just back out of the gas a bit until I feel the go back into lean burn mode.

I jokingly call it the opposite of vtec. You just feel the engine get a bit less powerful.
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Old 05-13-2009, 01:29 AM   #8 (permalink)
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I have 130k, and ran some fuel injector cleaner (Prestone). Will try the seafoam stuff, I saw it at Walmart and decided not to get it because I thought to myself how could 1 product work in so many ways?!

Will be doing the following soon
- Change MTF (Honda MTF)
- Change oil
- New spark plugs (OEM or ???)

I'll try to feel for lean burn mode tomorrow. I also saw a light covering of soot near the rear bumper. Not as much as my oil burning S2000, but enough to make me want to get it running a little leaner. I won't be replacing an O2 until a check engine comes on or my mileage drops way low.
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Old 05-13-2009, 01:59 AM   #9 (permalink)
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I am almost positive that you use regular motor oil in the tranny. I have it in mine. It makes me really fast. lol.

And the seafoam stuff... yeah it can be used in a variety of ways it does seem a bit gimmicky. But its pretty easy to use, what I did is I let my car idle, popped the hood, pulled a vacuum line off of the fuel pressure regulator thing (I can show you a pic if you want) and used the vacuum line to "sip" up about half of the can, which is kind of a lot maybe. But whatever. You have to be careful cause if you dunk the line, the motor will die. Its a trick to suck up as much as possible, as quickly as possible, without killing the motor. By the time you get to 1/2 a can left or thereabouts, you should have some white smoke coming out of your exhaust. Dunk the line, kill the engine, and let it sit. The longer the better. I let mine sit for almost a full 24 hours.

Then when you start it up, run the engine hard until it stops smoking. Running an engine hard while it is cold is never a great idea but in this case its important to blast out all that gunk while you have the chance.

It cleans out your vacuum system and your heads and your valves and your compression chambers and stuff. Good stuff to clean. My motor made TONS of smoke. Smoked out the whole street. The neighbors get angry haha but the smoke comes from dirt that your engine is burning. Good!

I did it again a couple months later and it made less smoke. I think its great to do every long now and then.

I also like to use the pyroil engine cleaner stuff once in a very great while before you do an oil change. You pour it in and let the engine idle with this stuff in the oil for like 5 minutes and it helps clean out that side of the motor. Just make sure you allow plenty of time to drain that old batch of oil out and maybe run a little bit of fresh oil through the motor to make sure as little of that pyroil stuff is left.

I hope you find these tips useful, I am not a professional mechanic but I do all of my own work on my cars like clutch jobs and everything and my friends are all mechanics. So take my advice however you chose.

Have fun!

EDIT: Also, I just remembered, see if there is any way to diagnose your MAP sensor. It also plays a role in determining air to fuel ratios, and one time some punk civic kid told me that replacing your MAP sensor is good for gas mileage... but who knows. I never did. This could be your problem but I could be way off.


Last edited by LeanBurninating; 05-13-2009 at 03:37 AM..
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