Worried about freeway fuel consumption recently. Getting 16 MPG...

[rick458]

clean out the EGR ports under the plenum cover, that WILL make a milage difference
also try some premium gas

[Tyler]

Only the 01-02s had the egr port issue, the 03 really did not have this issue.

[nsxtasy]

Originally Posted by Tyler

Only the 01-02s had the egr port issue, the 03 really did not have this issue.

Gunk builds up around the EGR valve and ports and needs to be cleaned out periodically or it will have a negative effect on mileage. I know it's true of my 2004 MDX so I'm sure it's true of a 2003 as well.

[Tyler]

OF course it is..should of known, always has to counteract my statements. The 03's up were not as problematic as the 01-02s and it does not have a big effect on mpgs. Keyword is "really"

[yogi799]

I have yet to take it on a freeway, so still cannot report if the spark plugs helped any. I will let you know as soon as I test it.

[mdxforever]

Can you read the Long Term Fuel Trim and Short Term Fuel Trim using on OBD reader ? while you are at it check if your O2 sensors are shot. Since you mentioned you dont feel a loss of power my guess is its dumping a lot of fuel which suggests a possible high fuel trim.

If the replacing the plugs didn't help reset the pcm (disconnect the -ve battery wire, wait a few seconds, fit it back on).

EGR port and circulation system clean up is definitely a possible cause and good suggestion to clean up. Dont be surprised if you end up spending way more than you saved on the cheap gas for fixing an egr or o2 sensor problem.

Edit: another thing I wonder is if your sparks plug didn't get changed out yet until 140k are you up to date on your other maintenance. General condition of the powertrain also matters. When was the last time the ATF and VTM fluids were changed ? What oil exactly are you using ?
You also have 40psi in your "cheapest I could get" tires which is probably more dangerous than helping 5% of fuel economy. sorry but all that doesn't say that you are taking good care of your vehicle.

[KRE]

Just completed a trip from Chicago to South Bend IN (Tire Rack). Just over 23 mpg on a 2002 going with strong tailwind. Only 18.5 mpg on way back pushing into 30 - 45 mph winds. Speed both ways 70 mph.

Maybe not your case but wind makes a difference.

Keith

[peejmeister]

Originally Posted by mdxforever

Can you read the Long Term Fuel Trim and Short Term Fuel Trim using on OBD reader ? while you are at it check if your O2 sensors are shot.

What would be good/bad Fuel Trim Readings? Also, is there a way to check the O2 sensors?

[Lietuviai]

We usually average only about 17mpg's but that includes mixed driving. The best we've ever done was about 23 mpgs and that was on one leg of a trip from Portland to LA. We've never really used premium UL in it and the few times we have, it didn't make any noticeable difference power or fuel economy wise.
One thing to remember is fuel economy is going to suffer from the the current type of fuel that is out there. Most fuels now have about 10% ethanol in it and that can affect fuel economy as well. You can expect to get even worse fuel economy if the EPA goes ahead as planned and allows up to 15% ethanol in the fuel.

[mdxforever]

Originally Posted by peejmeister

What would be good/bad Fuel Trim Readings? Also, is there a way to check the O2 sensors?

Swings +/- 5-6% is ok, I wouldn't expect anything over 10% - even if its close to 10% it would make me curious.

btw, if you have a obd scanner most likely it has an erase or reset function that will allow you to reset everything including the fuel trims, if that is the case no need to pull the battery cable. There is also a ecu reset fuse - I dont remember which one exactly and it could vary by model. It should essentially do that same thing. The battery cable method is most reliable but keep your radio code handy and it could wipe out your personal settings in memory(radio, seats, a/c, nav) unless newer models have a way to save those.

[yogi799]

Originally Posted by mdxforever

Can you read the Long Term Fuel Trim and Short Term Fuel Trim using on OBD reader ? while you are at it check if your O2 sensors are shot. Since you mentioned you dont feel a loss of power my guess is its dumping a lot of fuel which suggests a possible high fuel trim.

You may be right on the money... maybe... I don't know anything about that but I do have a nice OBD2 reader which hooks up to a laptop and I get hundreds of readings.

My cousin once stood near my tailpipe and when I started the car he said it smelled like fuel, so could you perhaps be right???? He just said that a month ago so it was right when my consumption was very high.

I will look up the values you have mentioned and report back. Do this on a hot engine, right? Anything else while I'm at it? There are a tonne of stats from ODBII when connected.

PS. How would the trim be corrected if the values point to a problem?

[AmanM]

After reading this i'm thinking of changing my spark plugs as well, been noticing my mileage decreasing like crazy, i used to get 400 ish kms on a full tank, now it barely gives me 350 kms. How often should you change the spark plugs?

[Tyler]

I change them every 60,000 although they say the iridium ones can go till 105,000. IMO that is some marketing bs.

[mdxforever]

Originally Posted by yogi799

You may be right on the money... maybe... I don't know anything about that but I do have a nice OBD2 reader which hooks up to a laptop and I get hundreds of readings.

My cousin once stood near my tailpipe and when I started the car he said it smelled like fuel, so could you perhaps be right???? He just said that a month ago so it was right when my consumption was very high.

I will look up the values you have mentioned and report back. Do this on a hot engine, right? Anything else while I'm at it? There are a tonne of stats from ODBII when connected.

PS. How would the trim be corrected if the values point to a problem?

Checking trim on cold engine is ok but O2 sensor graph should be when hot.
Is this your first winter with this car because with the temps you have up there it's not a good time for tuning fuel efficiency, unless your are saying you have got much better gas mileage in the past in winter too.

Causes can be several. Maybe your injectors are clogged. Maybe you have carbon buildup that has increased the comp ratio and its pulling the timing back too far and you are compensating with your right foot and thus the bad mpg.
If the o2 sensors are good then run a couple of tanks of good premium gas along with a good dose of fuel system/injector cleaner. Some unexpected causes of low mpg are bad wheel alignment and very frequent or constant AWD engagement - something not to be ruled out in your case with high tire pressure.
You didn't say anything about the condition of the power train fluids. That can add a fair amount of drag too.

[getyourmindrite]

Originally Posted by INGunGuy

Another thing that I have noticed is that if I set the cruise in my 2001 MDX I get around 24 - 25 MPG at 75 MPH which kind of surprised me. But if I try and keep the speed at 75 without using the cruise I am getting 21-23 MPG... which is another surprise.

INGunGuy

That's because Honda/Acura did it right, I heard some where that if you use cruise control you burn more gas but I use cruise all the time and average 23 mpg.