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Honda Civic GX Engine Questions



  • bank1avpbank1avp Posts: 78
    The ECO system CNG injectors have always been loud. Not sure why. Very simular to the factory GFI Ford setup but without the noise.
  • adeaadea Posts: 44
    yip_choi wrote: "The gas sold to us is 88-90% methane , the rest is propane, co2 , nitrogen ,water , and misc. contaminants."
    I just saw this so I need to reply. It really depends on WHERE you get your cng. When I first started using methane in '97 (had my '90 Toyota Celica GTS converted), I purchased it from FLEETSTAR at about $1.05/gge in AZ which was 99.9% pure methane made from LNG right at the site. It was the cleanest/purest you could get and my car ran great! (CleanEnergy bought them out and I still don't know how clean CE's is [does anyone know?]). Then I moved, so I had to use Trillium for a year and when I went to get my car emission tested, it FLUNKED :sick: on cng (HC), but passed on gasoline! A cng expert told me that it was the OIL used in the pumps that got in the lines and tank. When I bought my '00 GX I went to APS Electric here (they opened it to the public) and they told me that theirs was also 99.9% pure methane, and once again, it ran great! I just changed the fuel filter (only one high pressure in rear) at 118K miles, it didn't look that bad actually. :) So I would love to know the purity % for Trillium and CleanEnergy. Thanks.
  • adeaadea Posts: 44
    Just wanted to let all of you know that I just received my ScanGauge II. (free one day delivery!) I already diagnosed the check engine light on our other car and cleared the code, which put out the light. It took just a few seconds. (You can move it from car to car with no problems.) With the Honda Supplemental Manual, it has all the codes, so I'm planning on saving a lot of money diagnosing it myself. It looks like a great gauge! It is a tripper, OBD II scanner, and has a lot of gauges. It is made right here in AZ and has a one year parts and labor warranty. To have an accurate mpg readout, you have to calibrate it with a few fillups...with more making it more accurate.
  • Okay, I just bricked my civic GX. I closed the manual valve and ran the line "dry" by idling the engine until it stalled. I was diagnosing a fuel gauge peculiarity. After I reopened the valve the fuel gauge stayed at empty with the empty light blinking. The car refuses to turn over, and it won't even come out of park with the ignition on. Is there an excess flow valve I might have tripped with the transient surge into the empty line? How do I reset it? I think I located where it lives: behind the rear seat inside a rubber boot. Anyone with any ideas to reset, or must I tow to the dealership?
  • Update: I had an epiphany last night that I should try cycling the power. So after disconnecting and reconnecting the battery, all is well. Hmmm...
  • giorgigiorgi Posts: 8
    My check engine came on and my engine runs rough at idle. I did a complete tune up and I changed the coil. Check the code and it came up as cylinder 1 misfire. I took it into the dealer, gonna see what happens. Anybody had this problem on thier GX's? Mine is a 99.
  • giorgigiorgi Posts: 8
    Well I heard back from the dealer and they said that I needed a new set of injectors. They are very expensive. They wanted 500 for each injector. I told them I would get the injectors myself. Started looking online and found a place in Arizona that will rebuild them for 17 dollars each. I told them it was for a natural gas vehicle and he said they would do it. Yes!!!!!!!
    Here's the website if your interested:
  • jmonkjmonk Posts: 3
    Had the same symptoms with trouble codes (misfire) on all four cylinders. Brought it to my local mechanic and had to replace all four ignition coils. They had cracked with signs of heat scorching. Just over $50 a piece. It's a 2001 and only 58K miles. I'm hoping there is nothing else that caused this.
  • It IS very common for the coils to go bad , even at that mileage. Should be covered under the federal 8 yr /80,000 mile or calif. 15 yr/150,000 mile emmisions warranty on a SULEV rated car. The 01 gx is SULEV. Call honda customer service , I think you will be getting some money back. The coil towers go deep into the head, and really cook from all the heat.
  • jmonkjmonk Posts: 3
    Thanks very much for the heads-up on the warranty. I'll contact honda to check on reimbursement.

    One week later I'm noticing a random misfire and some performance problems on freeway acceleration. Hope it's not an injector problem. With 60K coming up, it's time to have a thorough maintenance check.
  • jmonkjmonk Posts: 3
    Many Kar Karma kudos are due you. I've contacted Honda CS and so far they say they will reimburse for this work. Thanks so much.
  • epnfrnepnfrn Posts: 87
    ok -- i'm at 30k on my 06, and have decided to replace both low and high pressure filters. i've read here and there that neither filter change is all that advanced for a decent home garage mechanic. i feel that i've also read that no-one but a trained CNG specialist should do them. if YOU have actually done one of these, i would like to get the exact protocol from you, as well as any suggestions/advice. if you have only 'heard' something about something ... please don't reply, as i've also 'heard' the same something (probably). based on what comes back, i'll either attempt it, or take it in to the shop.

    thank you very much,
    brian (epi)
  • I would love to observe someone changing the filters.
  • rojakrojak Posts: 1
    I'm curious if anyone knows there the warranty in CA for 150K mi / 15 years is documented? The only documentation I can find states 7yrs / 70K for CA, and for some parts its 8yrs / 80K. Although... I'm looking at this for my 1998 Civic GX...

    I have a similar misfire on Cylindar 1 problem, and it is seeming to be the injector for cylindar 1 being locked in the open position...
  • The CA SULEV emmisions designation was not even on the books until late 2000, so none of the 98 - 99 and few of the generation 6 California 2000 models have the 15yr/150k emmisions warranty.

    The CA SULEV rating is available to the manufacturer who wishes to make the vehicle qualify , and wishes to warranty for that long. It is not a mandatory rating.

    The generation 7 (01-05) and generation 8 (06 and later ) sold in those states do , and will be on the emmisions sticker under the hood.

    The rating is also only for the GX first sold in CA and I think MA, and NY. If you take it to other states, the federal warranty applies.

    On the fuel injectors, You could call Honda Customer Service and tell them a sad story and how much you love Honda products..... They may split the cost , like Honda pays for the part and you pay for the labor. Remember they have to listen to people complain ALL DAY EVERY DAY , and do not have to do this ,so be polite when you call !

    If that does not work out , internet Honda parts dealers like Bernardi, Majestic, or will sell them for about $350 each. 30% off list price. I have purchased from all 3 .
  • Brian.
    I have changed both on my generation 7 (01-05). The high pressure one is the same on all years to present. other than having to fabricate a tool to properly re-torque the housing cover to factory spec ( 30 ft lb) , it was no harder than changing spark plugs. 20 minute job, including r and r of the tank brace/filter cover.

    The low pressure filter on the 01-05 is a spin -on , exact same size as the oil filter , but it's red and has a thicker shell and different seal. NOT interchangable with an oil filter.

    On the 06 and later , I think the low pressure filter is an element in a housing. Never seen or done that one.

    The last time I changed filters , they were VERY clean and prob. did not need to be changed.

    Any southern california member of can borrow the tool from me , no charge. send a pm on that forum . Also can e-mail photos and info from the gx service supplement.

  • epnfrnepnfrn Posts: 87
    JL -- thanks for the reply -- i'm pretty handy in the garage, so with the description you've described (and other bits and pieces I've heard) I think this should be an easy job. I'll order a couple filters and check it out. I may email you when it comes time, should I see any major issues before I start.

  • freedmlfreedml Posts: 43
    It's ALMOST as simple as changing an oil filter.

    Close the CNG shut-off valve (every GX driver should know where this is, behind the left rear wheel). Let the car idle until it shuts off by itself.

    Here's the tricky part. Find a 2' long oil filter wrench.

    Unscrew the old oil filter and put the new one on. Open the valve, check for leaks, and start 'er up.
  • jc_autojc_auto Posts: 3
    Giorgi - did you send your injector to Accurate Injector to have it serviced? What was the result?
  • qb79qb79 Posts: 1
    I am new to this forum so bare with me, this may be a long post. I have read through the majority of the Honda Civic GX (CNG) threads since I own a 1998 Honda Civic GX and am having some troubles with it. Awhile back the check engine light came and it was idling roughly and would sometimes hesitate upon acceleration (as if some cylinders were misfiring). The problem seemed to be exaggerated in cold weather. So I took it to the local Autozone to have them hook up their computer to see what the computer said the problem was. It was reading multiple misfires and catalytic converter. So in effort to remedy the problem I replaced all spark plugs, wires, distributor cap, and rotor. However, that did not solve the problem.

    I also adjusted the value clearance since a few mechanics thought that may have been this issue but that didn't fix the problem either.

    So I settle for the last resort, I took it to the honda dealership CNG mechanic. He diagnosed that I need to replace all four injectors (550.00 ea), new fuel filter, and catalytic converter. He quoted me a total of something over 3000.00, which I had a hard time swallowing. So I paid for the diagnostic and to have them replace the fuel filter but I held off on the injectors and catalytic convert since I figured I could get them cheaper online.

    I found a site that refurbishes CNG injectors ( and sent my injectors in. They claimed they were able to refurbish 2 of the four. So I bought two new ones from Autozone. The injectors from Autozone look exactly like the originals and were only 167.00 a piece with shipping. Has anyone had luck with CNG injectors from Autozone? I am a bit suspicious of them since they are half the price of the other cheapest online injectors I could find.

    Once I had all four injectors (2 refurbs and 2 new from AZ) I installed all four but the check engine light came on again and it still idled a bit rough and hesitated upon acceleration at times. I was able to drive it around town fine but it just wasn't running up to par.

    So I researched about troubleshooting faulty catalytic converters and found out that engine sputters, hesitation or unequal power may result from a bad catalytic converter. Also, I noticed at times on the freeway the car acted as if it had a govenor on it and this was one of the symptoms of a bad cata converter. After reading about these symptoms I was certain that was my problem. So I decided to remove the catalytic converter to see if I could determine whether or not it was bad. Upon removal I could clearly see that the insides were not intact; therefore, I performed a little surgery to help determine if blockage caused by the broken internals of the catalytic converter was causing the car problem. I completely removed the internals and reinstalled the catalytic converter but the check engine light is back on and the engine sputters (misfires) and hesitates upon acceleration still.

    Any ideas as to what the problem may be? Is it possible that some piece from inside the catalytic converter could have fallen out and causing blockage farther down the exhaust pipe? Could the lack of internals result in mis-representative O2 reading from the two sensors on the catalytic converter, thus resulting in sputtering and hesitation upon acceleration? I am all out of ideas. Any suggestion would be helpful. Thanks and sorry for the lengthy post.
  • adeaadea Posts: 44 is my story: I have a 2000 Honda GX and I used ONE time TRILLIUM brand cng fuel, and I only made it a few miles when I felt a miss in the engine. About ten miles later or so while on the freeway, my check engine light started flashing and it would hardly run. I limped home not knowing all the damage that was being caused by the plugged/open injector (oil from their pumps!), including catalytic converter, fuel injector, control module, 2 o2 sensors, plugs, wires, distributor, rotor, and anything else electrical under the hood that I can't remember right now. $2000 later, it now runs great and after a valve job, I obtained 50 mpg/hwy for the first time using my Scangauge II. This cool device will also read out your trouble codes, readouts for many functions such as mpg, actual mph, volts, rpm's, water temp, etc. and is also a trip computer! Overall, I can get 42-43 mpg and go over 500 miles with my two tanks. (extra one is behind the front seats). So, I would definitely replace your catalytic converter (bought mine online much cheaper than anywhere else). I also bought an injector from AutoZone and it has performed flawlessly for over two years now. And make sure that your bottom (secondary/after catalytic converter) o2 sensor is the correct one! Using your car year and model with online and AutoZone WILL NOT give you the CORRECT one and your check engine light will stay on, plus it will run roughly. Make sure you get the PART # from Honda, then buy it at AutoZone. It has a different shape than the top one, at least my 2000 one does. Now, if that doesn't solve your problem, make sure you get the actual Honda spark plug wires and plugs! That was the last thing that finally kept my check engine light out! They told me that the car is very sensitive and needs the actual replacement parts for that, and that was the only thing that they said that turned out to be true. LOL Good Luck! :D
  • robmmarrobmmar Posts: 3
    I have a 2000 Honda GX with a with a Keihin fuel pressure regulator. It appears that the diaphragm is showing serious signs of wear and is need of replacement. Honda sales the FPR for $2,041.00, and apparently owns all the rights to exclusively sale this part. My mechanic has tried silicone glue on the dipragm for the time being but a better fix is needed. The FPR part # is 16740-PDN-A01. Any suggestions would be appreciated
  • adeaadea Posts: 44
    That part number from Honda is the entire assembly...not so sure you would need that...autopartswarehouse has just the pressure regulator for under $100 with free shipping. I usually get my parts from AutoZone or Rock Auto Parts, but neither one of those seems to have it. Let me know what you find and if it fixes the problem. How did you know it was needing replacement without looking at it? Thanks!
  • jc_autojc_auto Posts: 3

    The Autopartswarehouse system is wrong...very wrong. Your first clue should have been that they list the same regulator for both the "GAS, D16Y7" and the "CNG, D16B5" even going so far as to show the GX as having the D16Y7 engine. Pretty sad website if you ask me.

  • I’ve got a 2009 Honda Civic GX and I’d like to see if I can squeeze a little more horsepower out of her by installing some typical performance upgrades like a high-flow air intake and opening up the exhaust. Can those kinds of performance mods be done on the GX cars without messing up anything else, like the on board computer, engine monitoring system, etc.? Please advise; thanks much! –

    - akkadian09
  • thoughs guys at "Accurate Injector Service" do realy good work . saved me 300 bucks on my cars fuel injectors . or .. for email . I also sent them my toyota fuel injectors and my dad sent them the fuel injectors out of his mercury marine boat engine. all with great results .
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  • I have a '98 GX. According to owner's manual and all the Honda dealerships, the fuel cylinder needs to be replaced at 15 yrs. This will cost >$7K, of which $6K is for the carbon fiber/fiberglass cylinder replacement.
    A number of on-line suppliers sell a similar-sized (14" x 40.2", 7.3 gal.) but heavier (244 lbs). steel cylinder for $864, made by the Argentine company Kyoshi, which does meet DOT standards for vehicle fuel cylinders. However, the Honda dealerships refuse to install that product for "liability" concerns (read: less $ profit margin).
    I have found a couple of shops, several hundred mi. from me (NoCal), who are certified to do CNG cylinder swaps, but they are concerned that the fittings for the steel tanks won't match the originals, won't know until they take it apart. This might mean extended period in the shop if more parts have to be ordered.
    Just today I spoke with a used car dealer who is trying to unload a '98 GX, has NOT changed the cylinder, and claims that it's not necessary, because none of these tanks have ever failed, so long
    as the vehicle has not been damaged.
    Any comments?
  • No need to change unless it's leaking or been impacted due to an accident. If you're concerned, seek out a licensed inspector to have it re-certified.
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