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Honda Accord Fuel and Fuel System Questions

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  • ray_h1ray_h1 Member Posts: 1,134
    California converted to gasahol January 1, 2003. I track my mileage and noted a mileage reduction from 32 mpg to 31.5. Four years later I'm still hovering between 30.5 mpg and 31.75 mpg. Taking the worst case calculation, I've only found a 4.69% reduction using recent mileage figures (30.5 mpg) with gasahol, compared to the best mileage (32 mpg) obtained with straight unleaded gasoline. I tried one tank of 91 octane unleaded premium and noted no perceptible seat-of-the-pants difference in power, nor any difference in tracked fuel economy. The only difference I did note with a full fill of unleaded premium was that my wallet was about $3.43 lighter for my effort. I've since only used 87 octane unleaded regular. Good enough means good enough. Alcohol has one particular property that's generally misunderstood but advantageous. It's miscible with both gasoline and water. Water, in the form of condensation from air (and air replaces gasoline in the tank as the gasoline is used ;)) will accumulate in the bottom the the tank. Predictably, it can accumulate to a substantial amount over time. The ethanol in gasahol will gradually and continually absorb and move this water accumulation out of the tank, through the engine during the combustion cycle, and out the exhaust pipe as steam. Once the vehicle's gas tank is rid of water, continued use of gasahol will prevent its recurrence. I suspect, but can't prove, that most reports of poor performance with gasahol are due more to the impact of initially moving water out of the fuel system than any inherent combustion problem with gasahol.
  • blufz1blufz1 Member Posts: 2,045
    Thanks for the info. My 02 V6 also seems to lose about 5% w gasahol. Never tried the premium in my auto. I run premium in my bass boat and yard tools for the extra detergents the premium claims to have. I run the gasahol only when I have to so that would seem to lend credence to your theory.
  • th83th83 Member Posts: 164
    Although there is no dyno evidence to back up the claim, I believe it makes a difference.

    I've been putting 93 octane in my 2007 Accord V6 for nearly 3k miles now, with only two tanks of regular: the original tank-full, and a full tank somewhere around the 2k mile mark. To be honest I couldn't really tell a difference for the first several tanks. In fact, when I first switched to 93 from 87, the car felt slower. That was likely due to the engine burning 93 octane using an ignition timing map optimized for 87 octane. However, after a couple of tank-fulls of 93, the car started to perk up a bit. Uncertain as to whether the added perk was due to the premium gas, the engine loosening up from break-in, or both, I decided to fill up with 87 and see what'd happen. I noticed a difference within half a mile of leaving the gas station. The difference wasn't startling, but it was definitely noticeable, and it became even more noticeable in stop and go traffic on the way to work the next day. The car just wouldn't respond as quickly as I'd come to expect of it. Throttle response was laggy and torque was missing throughout the powerband. Not only that, but my gas mileage for that tank was only 22 MPG, 2 MPG lower than the previous tank. While I'm sure the drop in mileage didn't have anything to do with the fuel itself, it was likely due to me having to put my foot deeper into the throttle to make up for the lack of power. After emptying that tank of 87, I swore that I'd only use 93 from there on out. I don't mind paying an extra $3 a tank if it gives me the responsiveness that I want out of my engine.

    I can understand why people don't believe that premium fuel increases the amount of power produced by these engines. It boils down to this: People are impatient and want instant gratification. In this case, they fill their Accord V6 up with premium fuel expecting instant results, and then, when they're two-tenths of a mile down the road and they can't feel an improvement, they immediately declare premium gas not worth it and let the world know they're not happy (and these people love message boards). Unfortunately, they're not willing to wait a tank or two to see what happens.

    Now about the waiting...

    From what I've read around the net, it takes at least 300 miles for the PCM to advance the ignition timing after the owner switches to premium gas. I've read that this is a safety measure that protects the engine from detonation in the case of a bad tank of gas.

    In other words, when regular fuel is used, the engine runs a "safety map", or an ignition timing map that is safely optimized for regular gas.

    Supposedly, this "safety map" is used for 300 or so miles before the PCM tests the waters again by advancing the ignition timing. If it immediately detects knock, the ignition timing will once again revert back to the safety map. However, if no knock is detected initially, the PCM will continue to advance the ignition timing until knock is detected. It will then dial back the timing a few steps to provide a safety net. This process tailors the engine's performance according to the grade of fuel used.

    Unfortunately, we'll never know for sure if this myth of extra power from premium gas is confirmed or busted as long as Accord owners refuse to have their cars dyno-tested. A couple of dyno runs would have this debate settled in an instant. All it'd take is for one person to go dyno their 2003+ Accord V6; one set of runs on premium fuel, and one set of runs on regular. I'd do it myself, but there are no shops in my area with dynos open to the public. The last one closed down months before I even got my new Accord. Unfortunately, I live in North Carolina, and not California, where there's a tuner shop conveniently located on every corner.

    *sigh*

    Until the day an Accord owner steps up to the plate and solves this problem once and for all, this will always be a subjective debate...
  • elroy5elroy5 Member Posts: 3,735
    I tried to say this earlier in this thread, and met with some resistance from other posters, (claiming the engine computer would immediately adjust for the premium). I had heard from Honda techs that it would take a few tanks to get the extra power. I also heard that one tank of regular would put you back at square one. It would be nice if someone would prove this one way or the other.
  • blufz1blufz1 Member Posts: 2,045
    A car mag tested prem vs. reg in a honda a few years ago and found there was no appreciable difference in pwr and mpg fyi. Having said that, I do think your info is interesting. I might try a tank or two for fun to see. You may be getting a cleaning effect of the extra detergents in the premium.
  • elroy5elroy5 Member Posts: 3,735
    What mag did this test? I would like some details. Not that I would switch to premium, in any case. But I have heard from good sources that premium will improve power.
  • blufz1blufz1 Member Posts: 2,045
    Sorry, I take a lot of mags and this was a few years ago. Motorcycle users have also tested and concluded that regular produces the same hp as premium. Hope this helps.
  • robr2robr2 Member Posts: 8,805
    IIRC it was Car and Driver. It was about 3-4 years ago.

    The only way to really see if using premium has any benefit is to dyno the vehicle under laboratory conditions.

    Seat of pants dyno can be wrong - especially if one wants to believe one way or another.
  • bf109acebf109ace Member Posts: 77
    Correct me if I'm wrong. I read the 2006 Accord 4-cyclinder 2.4L has a 15.40 Gallon fule tank. What's the reserve (in term of gallon)in the tank that will not be usable before the engine stops running? Will I be able to use up all 15.4 gallon?

    My experience has been that when I used up 12.50 gallon, the Empty Tank Warning Light is on. In one occation, I drove another 40 miles after the light was on. Then, when I filled up the tank I could only pump in 13.56 gallon.

    How much fuel (in gallons) is left when the warning light is turned on? Techically, will I be able to use up all 15.4 gallons. If so, will it do harm to the fuel system (i.e. deposit at bottome of tank will be sucked in the fuel system)?

    I don't intend to use up all 15.4 gallons but it's good to know what the bottom line is.

    Please share your experience. Any adice? Thanks.

    Richard
  • blufz1blufz1 Member Posts: 2,045
    I think they have been 17.1 from 98 forward. The most I have put into my 2002 is 16.6.
  • robr2robr2 Member Posts: 8,805
    I don't know the answer but be careful when running that low. Typically, fuel pumps are in the gas tank and the gasoline is used to cool it - run too low and you stand the chance to damage the fuel pump.
  • elroy5elroy5 Member Posts: 3,735
    The rated capacity is 17.1 gallons. The light will usually come on at about 13.5 gallons on my 03 Accord (same size tank). Do you actually want the car to run out of gas for some reason? 17.1 minus 13.5 would be 1.6 gallons, so for my car I could go about another 40 miles easy, after the light comes on. It's nice to know how far you can safely go, if you're particular what kind of gas you want.
  • blufz1blufz1 Member Posts: 2,045
    I set my B trip meter to 0 when the E light comes on. The best I've done is 60 miles after the light come on.
  • mrbill1957mrbill1957 Member Posts: 823
    17.1 minus 13.5 would be 1.6 gallons, so for my car I could go about another 40 miles easy, after the light comes on.


    I think you mean 3.6 gallons.

    Mrbill
  • elroy5elroy5 Member Posts: 3,735
    Thanks Mrbill, hit the wrong number. :(
  • thegraduatethegraduate Member Posts: 9,731
    The fuel capacity has been 17.1 gallons. Possibly before 1990. My 1996 is 17.1 as well.

    Just wondering... where'd the 15.4 gallon idea come from?
  • bf109acebf109ace Member Posts: 77
    I got the 15.4 gallon capacity from 2006 Honda Accord brochure. Any info. in the owner's manual?
  • dudleyrdudleyr Member Posts: 3,469
    I recently filled up just as the light came on and only put in 13.6 gallons. This leavs 3.5 as the reserve.

    The owners manual states that there is 2.7 gallons left once the light comes on plus a small reserve amount. Seems like that small reserve is .8 gallons to make up the 3.5.

    In city driving there are too many variables, so I would probably just fill up before the light comes on or shortly after. On the highway, where I know what my mpg is, I may push it a little and use up 1 or two of the reserve gallons - leaving at least 1.5 gallons.

    Of course 2 gallons at around 35+ mpg is 70+ miles - that is a long way to drive with the light on, and may be hard to do psychologically.
  • bf109acebf109ace Member Posts: 77
    Just came back from a trip to D.C. The empty tank light went on and I drove for another 25 miles. When I filled up the tank, I put it 14.5 gallons. So I still had about 2.6 gallons left in tank, including the 0.8 gallon reserve.

    So the reserve means: it cannot be used at all. As a result, only 16.3 gallons of fuel can be sucked out of the fuel tank. If for highway driving, it convert to almost 500 mile range (16.3 x 30mpg).
  • thegraduatethegraduate Member Posts: 9,731
    Interesting. My brochure listed it as 17.1 gallons. The CR-V however just might be in the 15 gallon range, but I'm not certain. The owner's manual will confirm the 17 gallon figure, but I can tell you firsthand that I've put over 15 gallons in my car before in a fillup (ran with the light on for about 60 miles).

    Car and Driver and Motor Trend (as well as Edmunds.com for that matter) will have the info you are looking for, but ALWAYS check your manual and take it as the last word.
  • tallman1tallman1 Member Posts: 1,874
    06 and 07 Accord fact sheets list the fuel tank capacity as 17.1. My 06 owner's manual lists it as 17.09 (P. 266 and very last page).
  • b36b36 Member Posts: 15
    Does anyone know where this relay is located? I have been told only the mitsuba relay is a problem. If the relay is a denso it is ok. Seems like you shouldn't have to give your vehicle up for a half day if you have a relay that does not have to be replaced.
  • elroy5elroy5 Member Posts: 3,735
    Under dash fuse/relay box, bottom far left.
  • ldjackson53ldjackson53 Member Posts: 1
    How common is it to replace a primary O2 Sensor on a Honda SE 2002? I have had to replace mine for the last 2 years> Luckily, the first replacement was under warranty but the second one wasn't almost exactly one year later.
  • kriswrightkriswright Member Posts: 2
    I just bought a 1986 Honda Accord. It was running fine for the first week, but then it cut off while i was in traffic. i was able to get it started again a couple hours later, but only after giving the fuel tank a few whallops and putting the gas all the way to the floor. it's started a few times since then, and i was even able to drive a little ways without it cutting off, but now it won't start at all. i put some marvel mystery oil in the gas, and then it started giving me problems shortly after that. (coincidence? i'm not sure). i put some fuel injector cleaner in it two days ago, but to no avail.
    what should i do to get this hunk of junk moving again?
  • mrbill1957mrbill1957 Member Posts: 823
    If hitting the tank was your actual fix, then I'd say you looking at a new fuel pump.

    I've seen tow truck drivers come to a call, get out, wack the fuel tank, and have the owner try starting their vehicle again. When it does, he smiles, hands them their minumum trip charge, and drive away.

    Mrbill
  • kriswrightkriswright Member Posts: 2
    thanx mrbill. i came to the same conclusion with my stepdad about two hours ago. i'm about to look on ebay to see if i can find one.

    kriswright
  • neverwascoolneverwascool Member Posts: 1
    I have a 1990 Honda Accord that normally runs great. I just got it a couple months ago and haven't had any real problems with it. Now I have a problem: I was on "E" , and gas prices being what they are, I decided I would use a 2-gallon gas can with what smelled like gasoline to get me where I needed to go. This is where the problem comes in: I have no clue what that mystery liquid was, but after about 5 minutes of normal driving, the car started to chug. I made it about 2 miles, shut the car off, then tried to restart it, with no luck. Can someone please tell me how to get my car running again?

    The three possibilities the mystery liquid could be are kerosene, deisel, water, and or watered down gasoline.

    These are some things I know about whats going on:
    The car is getting spark
    fuel treatment didn't work
    the fuel pump is working
    properly
    Someone please help me
  • rick105rick105 Member Posts: 2
    my 86 accord idles rough,tries to run out of gas on a hill at times,have to pump pedal to keep it going. also on highway if you hold it to floor goes to 4-5 grand & starts cutting out like a rev limiter.i seen on here it could be the coil not sending enough juice to the fuel pump.any other ideas.also does anyone know what the vacuum diaphram on the drivers side of the carb. controls? thanks
  • skuddbusterskuddbuster Member Posts: 2
    Anyone know the actual fuel capacity of the 1984 honda accord lx hatchback? my owners manual says 15.8, but i have ran this thing almost dry and can only put about 11 gallons in it. I just bought it recently with 86k on it, great shape, just cant get the fuel econony accurate due to the tank size issue.

    Thanks for any info
  • elroy5elroy5 Member Posts: 3,735
    You don't have to know the size of the tank, to figure mileage. do it this way. 1) Fill the tank (stop pumping at the first click) 2) reset the trip odometer (before you drive off) 3) drive till the low fuel light comes on (or when ever you like) 4) Stop at the same gas pump as before (if possible) and fill the tank again 5) Before you drive off !!!!, note how many gallons it took to fill the tank (from the gas pump), and how many miles are on the trip odometer. 6) Divide the miles by the gallons to get miles per gallon. Example: 380 miles divided by 13 gallons would equate to 29.23, or a little more than 29 miles per gallon.
  • thegraduatethegraduate Member Posts: 9,731
    Elroy is exactly right. Tank size is completely irrelevant to determining actual fuel mileage. Use that method (I do) and you'll get accurate mileage, assuming your odometer reads correctly.
  • skuddbusterskuddbuster Member Posts: 2
    well, sure I understand that formula, and have used it, however my main concern is the actual capacity of the fuel tank, I was hoping there was some standardization and that someone could let me in on it.

    THanks
  • mrbill1957mrbill1957 Member Posts: 823
    The capacities for an 1984 Accord listed in a repair manual:

    oil w/filter 3.7 Qts
    trans 5-Spd 5.0 Qts
    trans auto 6.0 Qts
    Fuel 15.8 Gal
    Cooling system 6.4 Qts

    Mrbill
  • johnnyjlealjohnnyjleal Member Posts: 1
    i just bought a a 1990 accord, my car stopped running shortly after i checked the pump its running fine i spray starter fluid into the fuel injectors it starts but dies shortly after, any ideas?
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