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Old 02-15-2012, 06:12 PM   #1 (permalink)
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Hello, just bought HX civic!

Hello, just purchased a 98 CVT HX Civic for my commuter. Would like to learn more on here to get 50+ mpg from an automatic. Starting with grill block, underbelly, and scangauge!

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Old 02-15-2012, 06:29 PM   #2 (permalink)
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Congrats on the Civic Dgreen78. Its a nice car.

I don't want to burst your bubble but 50+ on a CVT HX is really pushing it. If you check the garage you'll see most HXs (with manual trans) getting in the high 30s to high 40s. Not to say it can't be done, but it'll require a lot of modding (aero mainly).
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Old 02-15-2012, 06:42 PM   #3 (permalink)
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Thanks for the reply, I know it will take a lot of help

I'm trying to figure out more about the lean burn and why I only have a 4 wire primary o2. I thought all the hx models had the wideband? Is their any indicator when it is in this mode? Will the scangauge II tell me?
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Old 02-15-2012, 09:12 PM   #4 (permalink)
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You should have a 5 wire. Make sure "D16Y5" is stamped on the block. Also, re count just to make sure.

Also, a scangauge is not your best friend with this car. It will not be as accurate as with a standard engine car. Your HX has a lean burn engine, which changes the air/fuel ratio during light driving loads so that you get better gas mileage. Since the scangauge and other products measure MPG using a fixed air/fuel ratio in their calculations they cannot account for lean burn mode and will give you inaccurate readings. To fix this issue MPGuino was developed which measures MPG differently. This is what you want on an HX or VX.

50 MPG with the CVT will be very hard. Depending on how much effort and money you want to put into the car, I would consider changing the CVT to a manual. It has been done before and I believe there is even a writeup on it somewhere out there. You can easily get 35-40 though. Heck, my HX with one cylinder not having compression got 32 mpg on my last tank.
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Old 02-15-2012, 09:49 PM   #5 (permalink)
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Yes, it has the stamp on the block. It looks like all auto ECUs use a 4-wire 02 sensor. Im still confused as I thought the 5-wire wideband was a necessity to get into LB mode?

36531-P2E-A01 (fourwire)
used on 96-00 cali & 49state CVT trans

36531-P2M-A01 (wideband)
used on 96-00 cali & 49state manual trans

I think I will try and run both the scangauge and look into purchasing a MPguino. I do like the features of the scangauge (clear codes, check TPS, Coolant temp, etc).

As far as swapping transmissions that looks like A LOT of work. I do like having an auto for a commuter. I also picked up a spare CVT at a local yeard for a mere $80 for a back up. It took me about an hour to pull the CVT out of the donor. Gotta love working on these civics!

The car does have some hesitation at low RPM even after a full tune up. I will be doing a compression test, cleaning of the idle motor/TB, and checking the timing to see if it is off a tooth. I am thinking it might be the CVT trans slipping as I have read problems with the start clutch and belt.
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Old 02-15-2012, 10:08 PM   #6 (permalink)
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Hmm why would the auto have a different O2 sensor? I did not know that. I am with you in thinking the 5-wire was required to do lean burn, which is why I assumed all HX's had them.

Many people with HX's run both the scangauge and MPGuino. The scangauge is nice because it gives you all that info.

Swapping trans. is quite a bit of work, but if you can pull out a CVT you should have no problem putting in a 5spd. The best route to take would be to find a donor 5spd civic and pull of all the parts you need. That way everything is already there you just need to swap the parts out. But like I said before you should have no problem with 40 mpg with the CVT so it might not be worth it to swap to 5spd.

I reccommend the compression test if all of your other efforts fail. I bought my HX about 1 1/2 years ago. I didnt notice until a month ago that the check engine light bulb had been removed. Turns out I had a CEL this whole time! It was for a misfire but I hardly noticed because the car still ran pretty well. I did a compression test trying to figure out why its misfiring and I had only 25 PSI in cyl. #2.
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Old 02-15-2012, 10:13 PM   #7 (permalink)
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Quote:
Originally Posted by cbaber View Post
Hmm why would the auto have a different O2 sensor? I did not know that. I am with you in thinking the 5-wire was required to do lean burn, which is why I assumed all HX's had them.

Many people with HX's run both the scangauge and MPGuino. The scangauge is nice because it gives you all that info.

Swapping trans. is quite a bit of work, but if you can pull out a CVT you should have no problem putting in a 5spd. The best route to take would be to find a donor 5spd civic and pull of all the parts you need. That way everything is already there you just need to swap the parts out. But like I said before you should have no problem with 40 mpg with the CVT so it might not be worth it to swap to 5spd.

I reccommend the compression test if all of your other efforts fail. I bought my HX about 1 1/2 years ago. I didnt notice until a month ago that the check engine light bulb had been removed. Turns out I had a CEL this whole time! It was for a misfire but I hardly noticed because the car still ran pretty well. I did a compression test trying to figure out why its misfiring and I had only 25 PSI in cyl. #2.
Thanks for the recommendations. I will have to do more reading as to how the auto and manual ECUs operate with the different sensors.

Wow, that is pretty low removing the bulb. It takes a real low life to pull something like that Do you plan on rebuilding the motor or finding another? I am amazed the deals you can find on Craigslist and car-part.com (junkyards) for used motors and trannies for these cars. Their was just a complete long block on my local listings for 200 including trans! I just checked your state and their is a motor with 200K on it for $200, might be worth looking at.
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Old 02-15-2012, 10:35 PM   #8 (permalink)
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I think maybe the auto trans didn't have lean burn?? Also there's Cali emissions and 49-state emissions. Sorry I'm not being very specific, it's because I don't have the specifics. But I do think the auto version might not have lean burn, very sorry if that's indeed true.
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Old 02-15-2012, 10:35 PM   #9 (permalink)
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I could not find any lower mile longblocks around so I just decided to buy a remanufactured motor off eBay. It was pretty expensive at $1500, but its basically a brand new engine. I plan on keeping this car for a long time and the body is in great shape so it was better for me to just invest the $1500 now and have a great running car versus buying a used motor (if I could find one) that could potentially have problems later on.

Im pretty excited to put in the new motor. Should be arriving tomorrow. I have been getting about 34 mpg in the last couple months so it will be interesting to have a nice new motor and actually be able to use lean-burn again lol.

EDIT:

This is a pretty interesting read:

http://www.civic-hx.6thgearadvertising.com/

It explains that indeed CVT uses 4 wire and manual uses the wideband o2 sensor. Also, the IACV on the CVT has 3 wires vs. 2 on the manual. But I think the CVT still has lean-burn because they probably wouldn't put in a D16Y5 and simply disable the lean burn. If they did thats pretty lazy engineering. But according to that guy it has lean burn but it still doesnt explain why the CVT didnt have the 5 wire sensor.
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Old 02-15-2012, 10:42 PM   #10 (permalink)
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That sounds great, I think you should have a nice bump in MPG! Good luck with your car and post the results when you get a chance.

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