dlb

Have read the site before, but new to registering.

I have a problem with the Accord I hope I can get some help with.

I have a 2005 Accord EX 4 cylinder with 60,000 miles that used to get awesome gas mileage. I changed the air filter because it was dirty and installed a K&N. After I did that, the mileage went from 36 to 22, so I switched back to a paper one and gas mileage went up to 25. It's driving fine, no hesitation, haven't changed driving habits, run nitrogen in the tires, they've been rotated and aligned, so I'm not sure what else it might be...

Any help?

speedracer9k

nitrogen in the tires??? that is the biggest load of crap i've ever heard. How does that benefit? is it lighter than air and makes your car go faster with better gas mileage? ambient air is already 79% nitrogen. how does the other 11% in your tires help?

KWayRacing

Whether you agree with nitrogen filled tires is your business. I don't either but telling the OP your opinion about N filled tires is useless info.

KWayRacing

Incorrect, especially low,tire pressures can affect both tire wear and fuel mileage. Even though they are N filled are they at the right pressures?
36 -22 is doubtfully possible with correct measurements and no difference in operating conditions and no mil illuminated only from a filter change. How are you conducting your mpg testing? The only real way to evaluate engine efficiency is by analyzing live scan tool data. Paying special attention to ST fuel trim and LT fuel trim values. For Hondas fuel economy concerns are seldomly found to be an actual problem with the engine/systems but rather a flawed testing method. However, I have repaired several fairly low mileage vehicles before for real fuel econemy issues with no CEL before, so I am not dismissing the possibilty.

speedracer9k

the point i'm trying to make is that nitrogen filled tires are a waste of money. shops will charge up to $100 just to convert your tires to nitrogen. it's a big waste of money. and how many gas stations can you pull up to and fill your tires up with nitrogen? none that i know of. how hard is it to check your tire pressures every now and then.

kway: i agree with everything you say in your post about live scan tool data, fuel trims, and mpg testing.

KWayRacing

I agree N is crap, but the op wants help with mpg.

Dan8yourV8

ttttt

PowerUser

How about instead of riding on what the OP puts in his tires HELP him with his mileage problem.

I suspect that a couple sensors need to be cleaned. I'd look in to cleaning the mass airflow sensor. A dirty sensor can lower your mileage yet still not throw a check engine light.
Do NOT use anything except mass airflow cleaner on the sensor.

KWayRacing

eggzactly

George Knighton

If you were getting 36 miles per gallon in a 2005 K Motor then you were shifting absolutely perfectly and doing exclusively highway miles. :-)

Supposing that, my next guess is that you are now fooling with the car in ways that you haven't been for tens of thousands of miles, and you're simply driving differently.

A change in air filters that affects the fuel mixture will cause the computer to hiccup while it settles in to what is doable with the new air flow...but this is a more or less theoretical problem that I have never seen make this drastic a difference in fuel mileage. In other words, if the new free flow filter allows enough air for the mixture to potentially lean, then the computer will feed more fuel to make it safe and then it will take a month or so to learn about how this new mixture works and maximise the power and fuel economy.

I have never seen a change in air filters make this kind of difference, and I really think you're just driving differently while you are playing with the car.

I cannot think of any reason why a change in air filters would make the kind of drastic difference in mileage you are mentioning.

Targa250R

It's possible that the MAF sensor could have been contaminated with filter oil from the K&N, or you may have inadvertently mishandled it during filter removal/installation. Try cleaning the MAF, which is the sensor located on the air filter box lid next to the snorkel port. There is a special formula sold in spray cans specifically for cleaning Mass Air Flow sensors. If you can't find it, you could probably try some carb & throttle body cleaner. Do not touch the sensor itself when cleaning; you may damage it. A new sensor costs about $139.

dlb

Thanks for all the information.

The Nitrogen was free and where I work it's used in all our cars after they did testing at several speeds.

The mileage problem is still there several weeks later even going back to the paper filter. The pressure is right in all the tires and I haven't done anything to the car part wise or anything like that. I drive normally as I have a work car I can dog and drive how I want. I've driven the same way to work every morning since I bought the car and usually try to use the cruise control and that hasn't changed.

I'm still lost. I'll try to clean the MAF and see if that helps I guess...

Anything else you all can think of?

KWayRacing

Yes. Try performing the idle learn procedure. To accomplish this remove the negative cable from the battery. Wait 3 minutes. Reinstall negative cable. Crank vehicle with all loads off(headlights, A/C, blower motor, radio,etc.) Let idle 10 minutes. Reset radio codes, should have since purchased new. Reset autodown window control( hold open switch down for 3 seconds after the window has fully opened, auto up equipped vehicles repeat when raising window. Your done. I doubt this has much effect on the MPG, but this can't hurt the cause. If you do not want to wait the 3 minutes you can remove the positive cable also. ANd while both are DISCONNECTED touch them together. This instantly clears all capacitors memory. Again, its hard to believe such a large difference can be attributed to air filter change only. Inspect your installation making sure all hoses/ fittings in the intake tube from the filter housing to the throttle body are connected correctly. Recheck and verify mpg testing procedures. Good luck.

HondaFan6975

Probably had too much oil on the K&N filter I'd follow everyone's advice on the MAF sensor and also I'd clean the throttle body too.

dleccord

Who would pay or charge $100 for nitrogen.

Costco does it for free for their customers.

KWayRacing

nitrogen filled tires..... what a sham.

97civicdx

The whole theory behind using nitrogen is it more stable and not as affected to temp changes. It also doesnt break down the inside of the tires as quickly as using air.
You can top up a Nitrogen filled tire with air temporarily but it should be purged with nitrogen when you get a chance.


I have access to an air compressor so I wont use nitrogen. To each his own about converting over to it.

z28matt

The nitrogen holds air better when its cold, but for the price of that i'll just buy a compressor and fill them up every night. But thats beside the point, i'd say clean all of your sensors on your air intake, because they got oil from the filter.

bobbyj59

Sorry to dredge up an old post, but I am a new member with almost the exact same problem. My wife's 2005 Accord EX automatic with 110,000 miles has seen a sudden drop in mpg, probably since the car turned over 100,000. We are very accurate about our record keeping and we know what kind of mileage we would normally get out of a tank of gas. Her mpg dropped from 30mpg to about 22 mpg (city/highway combined). SO far all I've done is change the air filter (Honda) and used some Techtron but still no change.

I am curious if the original poster to this thread was able to solve his problem and how he did it?

I will try the Mass Air Flow Sensor cleaner and report back. Any other ideas? A local mechanic recommends checking/changing spark plugs; cleaning fuel injectors; a "carbon cleaning" of the engine with a MotorVac machine. I'm a little dubious about that last procedure; anyone aware of it?

Bob Jordan

GoLowDrew

Motorvac is something they hook up to clean the fuel line. Imagine a pressure washer. Pump water (cleaning solution) in, run through all the lines, and out another way. You seems to be a guy that knows how to take care of his car, so I can't imagine your engine is that dirty and need to go on dialysis.

That's seems to be the standard fix recommended for all symptoms. Do you think it could be the spark plugs, and etc? Good for $100-$200. And if the problem don't go away, they got you hook on for more service. You arealdy poured some Techron, it's clean.

I would try reset the ECU. With a warm car, disconnect battery. Wait 20 min. Start engine. Let it idle for 5-10mins. Turn off.

I would also check the alignment. Does the car track straight? Wear patterns on tires? Does your transmission feel ok?

Targa250R

Honda recommends changing the spark plugs at 110,000 miles. If you haven't changed those yet, do that.

bobbyj59

Thanks so much for the replies.

The alignment is fine, air pressure (normal air) is always checked, no abnormal tire wear.

I'll try the spark plugs and ECU reset this weekend and respond back.

Bob Jordan

johnnykash

id say stop booting it everywhere and drive normal, thats why my fuel mileage sucks

jolie12

Hey its good to know.Its really wonderful posting you all have did.Thanks for making us aware of it.It was good to know.