Ok guys - I am new and this is probably easy money for someone out there. I have a 2000 4 cl coupe. DX model I believe. About a year or so ago I had dipped down to about 340 miles per tank. I changed my plugs wires,got a cold air intake along the away, used some sea foam in the intake and gas, and all was fine. About 400 miles per tank. NowI am back to 320 - 360 range again. I checked the plugs and htey look fine. I cleaned teh filter on air intake - it also was fine. I change my oil regularly (castrol high mile).

What can be my problem? Fuel filter? If so, why does autozone say I need to change the fuel pump too?

I am in dire need of a transmission fuel and radiator coolent change.

Thanks for the help, and I hope there are not a bunch of threads out there helping with this. I don't want to get yelled at like some of the other new guys!

Zack
2000 Accord
4 cyl
~110 k miles

 

a cold air intake decreases mileage, just an fyi.
Short ram intakes increase mileage.

 

???????? How is that possible? please explain.

 

I got the intake before the issues, and to be honest it did help. I lived in Dallas at the time, and literature thatI read the cooler air vs hotter engine compartment air (with short ram) helps with HP and gas mileage. Every 1 degree less = x more hp and fuel efficeiency.

I guess my issue stems past the potential intake issue. My wires are fine, plugs are fine, oil is good, filter is clean, so what else should I be looking for?

 

Check the O2 sensor. That will decrease gas mileage.

 

Yeah but nafango2 said that the CAI decreases mileage while SRI increases mileage. Don't see how that works out unless you can give me an explanation.

As for your problem how long have you noticed the drop in mpg? I think it is better to calculate your mpg rather than how much you can run on a tank. Your fuel gauge could be off so you think you're empty when you're not. Is the amount of fuel you're putting in same as before you noticed the drop in mileage per tank? In the future the best way to keep take of your fuel mileage is to fill it up, reset trip meter, run till about 1/4 tank, refill and calculate your mpg.

 

The best milage calculation is over a long period of time, do your weekly or biweekly checks but add everything up over a couple of months too, you will see a difference, it is also believed that many calculations can be off by as much as 25%, read that somewhere.

You need to see what the MAP sensor voltage is at idle, it should be just under one volt, much over one volt will require a valve adjustment. Tire pressure is another killer, not sure where you live but cooler ambient temps lowers tire pressure, this is an item that needs to be actively monitored. Inspecting the activity of the O2 sensor really needs a good understanding of what a rich biased sensor looks like, but the average tech with some training will know if it is just in bad condition, today, the scan data for fuel trims will tell the story of the O2 keeping control over fuel delivery also.

 

To answer some of that - its the same amount of fuel each time. I have gone from ~28.5 city / freeway to about ~24. I guess its not that bad, but in correlation to mywork commute its a loss in a day of travel.I used to drive about ~26 miles each way. So, losing 60 miles to a tank hurts me pretty good. The car has a lot of miles (still has a lot to go), so I am sure it is just something maintance wise....

What about fuel injectors. I had one go bad once and I smelled gas - strong gas. Can they go bad without an odor?

 

"Check the O2 sensor. That will decrease gas mileage."

Can you expain in more detail as to why?

 

if it's bad, your ECU isn't going to trim the fuel properly hurting MPG

Try a can of Seafoam