Civic bad Mpg help

[Kyle]

Lousy gas they're selling now days.

This has passed through my mind a few times but I have never given it any real credit. I supposed it could be a contributing factor. It just seems to have plummeted lately after a period of slow decline.

What kind of plug did you put in it? Also the content of alcohol in the fuel can greatly decrease the milage as it doesn't put out near the BTU's as pure gasoline.

I put ngk plugs in.

+1 ... Once they started mandating ethanol in the gas, my mileage took an easy 3-5 mpg hit... Used to get 20-21mpg out of my truck.

Playing "CALL OF DUTY IX: DOUGHNUT WARRIOR" does not make you a "cop". -wakal

Typical... El presidente Mandates that vehicles get better mileage... Allows fuel quality to slip, causing poorer mileage...

 

[35Remington]

Oh to have this problem! I get one-third the "bad MPG" you are complaining about.

I would start with a bottle of fuel injector cleaner on the next gas fill-up, but I am no mechanic. Best of luck.

 

[Kyle]

Oh to have this problem! I get one-third the "bad MPG" you are complaining about.

I would start with a bottle of fuel injector cleaner on the next gas fill-up, but I am no mechanic. Best of luck.

I'm sorry you have to drive something that gets poor mileage. You may need that though. I don't right now so I need something that gets good mileage... So considering I am losing between 75&100 miles every tank and I put on 800-1000 miles a week, it is a significant loss.. If I didn't drive so much it wouldn't be a complaint but I am losing $9 on every tank I run through it.

Injector cleaner didn't make a difference.

 

[Leper]

If your tire combination didn't affect it and the a.c. didn't affect it and you have checked everything else, I really don't know what to suggest. Timing belt stretch shouldn't have that kind of effect, but you are about due for one anyway. I've never seen that model jump a tooth unless someone has messed with it. The O2 sensor could be the issue, but that would be an expensive guess. Did you put ngk plugs back in it when you changed them? Are they gapped at 1.1 mm? Is there more road construction where you are driving now? Have you checked the valve adjustment?
With all that said, i keep coming back to the a.c. issue. You say there is no difference. I have a hard time with that. That car is know for mileage decreases in summer. Especially during the switch from winter to summer fuel formulas. I would recommend throwing the stock tires and wheels back on and driving for a week just to get your baseline back. I wonder if your calculations

 

[Leper]

With the different ties are incorrect.

 

[Kyle]

I know what you are saying, I just haven't seen any appreciable loss due to running the AC.

My stock tires: 185 70R14 VS. New tires 195 65R15

Diameter- 24.2" - - 25"
Width - 7.28" - - 7.68"
Sidewall - 5.1" - - 4.99"
Circumference - 76" - - 78.4"
Revolutions per mile - 833.9 - - 807.8

Very little difference between the two if you ask me. but my guesstimate that roughly 40 miles = 1mile lost on my odometer is pretty close to correct. it works out to about 1.25 miles loss every 40 miles.. it varies a bit with speed increase and decrease.

It is only enough of a difference to account for 1 maybe 2 MPG loss.


My 02 sensor readings over about a mile taken after at operating temperatures. Cruise control set a 65.

Bank 1 sensor 1 - VOLTS .72, .11, .66, .17, .23, .68, .56, .76, .60, .72, .33, .13, .83, .48
Bank 1 sensor 2 - VOLTS .78, .76, .76, .76, .13, .23, .72, .70, .70, .16, .06, .47, .85, .66

 

[35Remington]

Throwing the old tires back on for a week is free, right? If money is your concern, that's a good first play.

 

[Kyle]

Throwing the old tires back on for a week is free, right? If money is your concern, that's a good first play.

Money is not necessarily the concern. This is infinitely better on gas than the car I had before. My concern is the sudden and steady decline in mileage though. That is a problem.

If I still had the old set, I would. not an option though. I gave them to a roofer who's tires had steel belt showing. He needed them a bit more than I did.. haha

I was getting roughly the same mileage for almost 2 months with these tires before I started seeing a decline so I doubt that is the issue.

Im seriously at a loss on this. Normally obvious things to check are all checking out. Ive been seriously digging on this for a bit over a month now and I am finally fed up and searching for some fresh ideas

 

[rsayloriii]

Have you noticed any gains in the recent past? I've picked up a little with the switch to summer gas hitting stores.

Playing "CALL OF DUTY IX: DOUGHNUT WARRIOR" does not make you a "cop". -wakal

 

[Kyle]

Have you noticed any gains in the recent past? I've picked up a little with the switch to summer gas hitting stores.

Playing "CALL OF DUTY IX: DOUGHNUT WARRIOR" does not make you a "cop". -wakal

maybe last month. I didnt see any gain, but I seemed to have leveled off for a couple of weeks at 30 MPG HWY.

 

[rsayloriii]

Have you checked the o2 output vs the manual?

Playing "CALL OF DUTY IX: DOUGHNUT WARRIOR" does not make you a "cop". -wakal

 

[Kyle]

Haven't had an opportunity to look at the numbers should be. Hopefully I can do that tonigh though. Some of the numbers,
based on what I have read, seem a little suspect.

 

[Kyle]

Finally threw a code. P1456... Evap system (I'll start with the gas cap and work my way thru) Also found I likely have a bad o2 sensor. My number 1 sensor is reading properly, but a bit slow. The second sensor, after the cat, is flat at .8volts.

 

[Recoil45]

Only the sensor on the engine side of the cat will impact gas mileage but it sounds like you probably know that already.

 

[Kyle]

Only the sensor on the engine side of the cat will impact gas mileage but it sounds like you probably know that already.

I suspected that, but with uncertainty so I appreciate the heads-up on that!

 

[Recoil45]

The role of the sensor behind the cat is to monitor the cat. At your milage, it is likely to be a bad O2. There is a small chance that your cat is clogged and your O2 is good, but it's not likely. A clogged cat would impact milage.

 

[Kyle]

The role of the sensor behind the cat is to monitor the cat. At your milage, it is likely to be a bad O2. There is a small chance that your cat is clogged and your O2 is good, but it's not likely. A clogged cat would impact milage.

The more I read, that's exactly what I am gathering.

I think I may pick up laser thermometer and test the temp at the in and out of the cat. The more I sit and watch the o2 sensor reading, aside from being a bit slow in their reading, they appear to be ok. The end o2 sensor seems to be reading pretty rich. I'm hoping it isn't the cat.... We will see though. I'm finding a few other, unrelated, problems as I dig... Always something!

 

[rsayloriii]

You could put a test pipe in place of the cat to test if it's plugged or not. If your mileage goes up, your cat is the culprit. You'll have to replace it though as leaving it off is illegal.

I had a car that had a rattle I couldn't figure out. Finally narrowed it down to the cat. Put a pipe in to test it, and amazing; no more rattle, but even bigger, probably 100% more power. Didn't know it was off before since I bought it used.

Playing "CALL OF DUTY IX: DOUGHNUT WARRIOR" does not make you a "cop". -wakal

 

[Kyle]

You could put a test pipe in place of the cat to test if it's plugged or not. If your mileage goes up, your cat is the culprit. You'll have to replace it though as leaving it off is illegal.

I had a car that had a rattle I couldn't figure out. Finally narrowed it down to the cat. Put a pipe in to test it, and amazing; no more rattle, but even bigger, probably 100% more power. Didn't know it was off before since I bought it used.

Playing "CALL OF DUTY IX: DOUGHNUT WARRIOR" does not make you a "cop". -wakal

I could use more power... Haha.

So is it illegal all over or just in areas that require emissions testing?

I just went out to look to see if that were possible but it appears that the manifold and cat are one piece. So that sucks. :/

 

[rsayloriii]

I could use more power... Haha.

So is it illegal all over or just in areas that require emissions testing?

I just went out to look to see if that were possible but it appears that the manifold and cat are one piece. So that sucks. :/

It's a federal offense to tamper with any emissions component.

Next best thing to do is the temp test.

Playing "CALL OF DUTY IX: DOUGHNUT WARRIOR" does not make you a "cop". -wakal