Couple of Questions about my 97 Civic Hx, lean burn, etc.. - Fuelly Forums
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Old 07-27-2008, 09:19 PM   #1
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Couple of Questions about my 97 Civic Hx, lean burn, etc..

Been viewing/searching the forums here for a few weeks now, Lots of great information Ive found thanks to all you guys

I recently found this car on craigslist for real cheap, needed a few parts, missing body panes, etc.. Someone had also Tried to turbocharge the car, and convert the car to a m/t.

I ended up pulling the hacked turbo kit off, finished the manual swap, got a l1h1 wide band o2, m/t hx ecu, built an adapter to use a ford 2wire IACV and got it running. I've put a good 2k miles on it, not getting that great mileage.
Cars seems to run great, I can see Vtec coming on through my snap-on scanner which im assuming is when the car goes into Lean burn mode? Or is there a few more variables im missing? I've noticed vtec comes on around 3k rpm's and stays till about 5-5.5k, doesnt make much sense. Babying the car around town it would make more sense that it would come on much earlier in the power band and be balanced enough to cover some higher highway rpms.

For the time being trying to see if I could get the car to run right somewhat i replaced a few things with other spare parts off a few other cars from the shop including a viper cat, viper downstream o2 sensor, ford mustang IACV, and i fabbed up an intake out of a spare K&N filter and alum i had at work. Car had some hoodrat exhuast on it when i bought it, i put the cat on the car, and took off the nasty muffler and put on a tad more subtle aftermarket muffler.

I havent seen any codes yet, Ive seen one pending code for some unfamiliar IACV circuit code, but it never set the light or a code.

I've noticed the car will never finish the o2 monitor under the global odb2 diagnostics, just just test not yet complete. If i go under data the Secondary o2 voltage doesn't seem to move through the scanner..... I've doubled and tripled checked the wiring, both sensors are hard wired directly at the ECU/harness, with the original pigtail connectors at the sensors. I've even tried an o2 SIM in place for the 2nd sensor. I couldnt find anyone who would sell me a factory exhaust with the factory cat right after the exhuast ports. so its got an EX factory two piece manifold. I;ve used a viper sensor on another obd1 civic of mine and it worked fine

The mileage i got out of the car to date, is about 330 miles. About half being light city driving, and 15 mins stints on the highway to work and back everyday. Since then its just gone downhill, maybe around 200-250 at the most. Unfortunately the car also has factory civic 15" wheels and tires off an earlier model. I believe and 05 model or so with steel wheels and 7 spoke hubcaps. So I'm not too sure how off my mileage is

Are these cars too picky for me to be tossing parts off other cars on it? Any help is greatly appreciated, im getting fed up with how much gas im spending driving this thing around, its supposed to my getting around FE dd.

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Old 07-28-2008, 09:21 PM   #2
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You can't put other car's parts on it. The ECU is calibrated to the factory parts. Lean burn cars are especially picky. But that is just a bad idea on any car. It may seem to run fine but poor mpg is a strong indication that something is wrong. Honda parts are extremely common and cheap so I don't know why on earth you'd try a Ford IACV. Is the Ford IACV even pulse-width-modulated or is it a stepper motor? What's your idle RPM (not according to the tach but from the diagnostic plug).

When VTEC-E solenoid powers up you're in 16 valve mode. Lean burn occurs in 12 valve mode, 0-3000 RPM, light load and light throttle.

Your manual trans needs to be from an HX for the ECU to control lean-burn properly. The gear ratios are different.

Go to tire rack .com and compare your rim size/tire's sidewall height to the factory rim size/tire sidewall height. If you keep the same aspect ratio then your speedo and trip meter will be accurate. You can also follow a friend on the freeway and have him maintain 70mph and compare that to your speedo.

You don't calculate mpg by "miles per tank". You calculate it using the tripmeter and your gas receipt telling you how much gas you used.


Civic VX, D15Z7, 5 Speed LSD, AEM EMS, AEM UEGO, AEM Twin Fire, Distributor-less, Waste Spark
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Old 07-29-2008, 10:09 AM   #3
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Should have skipped all that bother and waited for a genuine M/T HX! I get up to 508 mile tanks if all hwy.
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