honda gas mileage

[FabioB92]

I’m trying to find out what my o2, fuel trim, manifold pressure, engine temp, and any orther useful data to help diagnosis a gas mileage issuse. I drive a 2001 honda accord v6, with 95000 and when I first got it at 70000 I averaged 21 mpgs? And has anyone ever ordered the shop manual from the back of the owners manual, is it useful?

Topic

[college man]

what has your mileage dropped to? is it cold where you are?C8-)

[FabioB92]

I’m in pittsburgh pa this winter has been mild but my mileage is around ten mpgs and i got a list of part I replaced and I know throwing parts at a car is not how you fix it but. Most of then needed to be replaced , I used the torque app on my phone for a scanner but I probably need a honda comp but they didnt want to look ay my car cuz I had a cold air intake

[college man]

with that big of a drop sounds like your dumping gas. you don’t smell raw gas?

[Bad_dude]

Holly cow!!!
With the gas prices your car is robbing you. I have a 90 and I don’t know how similar but yours is a V6. My buddy has 2002 V6 and he gets 26mpg mix driving.
There are a few things that you can do to check:
1) Gas leak: Lift the hood and smell for gas. The car that age, the o rings could be going. All it takes is one. I already replaced my buddy o-rings and gaskets on all his injectors. While they were off, we soak them in the part washers with mild chemical agent. Lot’s of black nasty stuffs. And he’s only drive with Chevron gas brand. We did it b/c one of the o rings was leaking mildly so we did it. After we reinstalled every thing we checked for leaks, and listen to the ticking of the injectors to make sure they all are healthy. He’s been running Redline SI1 bottle every 50k miles and recently we took them apart, the injectors are pretty clean.

2) Clean the EGR valve and ports. These car are easy compare to my 90 where I had to drill all 4 ports and broke bits and all. http://www.youtube.com/watch?v=E-G8YFwueWE If you get bogging, this could be it.

3) I seafoam the car once and lots of junk came out.

4) Adjust the valves: http://www.6thgenaccord.com/forums/show … php?t=5211

5) How’s the plugs? Look at them, they tell you a lot of things. Even if they are only a few weeks old.

6) The o2 sensors. We replace the bank 1, before the cat even though the CEL didn’t go on. Some time the carbon deposit make it inefficient. But first test it. My friend just wanted to replace it. As for my 90 Accord, every one knows CB7 only have one o2 sensor and it does not like to throw a CEL for the sensor. My friend had a 92, without a CEL, we replaced the Denso o2 sensor on it and it went from 24mpg to 30 mpg. And this is with mix driving.

7) Check your manifold for cracks, that would definitely do it, but some times you can smell exhaust from the engine bay with the car running.

Good luck, if you need any more help go over to Honda-tech, chances are some one has the same problem as you.

[cb7ftw]

Also, check you gas. They may have changed on you. As they put more ethanol in, you will see a drop in gas mileage.
Summer and winter blends will change your mileage a lot.

Also, use the grommet from your stock air filter, for your air temp sensor, on you short air intake. Most grommets that come with the short air intakes are to think for the air temp sensor.

Pull your heat shield and check your exhaust manifold for cracks.

[dreamer2355]

Is your CEL on?

Do you have a scan tool that can show you PID data?

[johnzcarz]

As Dreamer said – do you have access to PID data? I’d be interested in looking at your LTFT and STFT numbers – that may help us narrow it down. With that big a drop in MPG, I would expect to see a big LTFT value.

If you don’t have access to them, I wonder if a parts store would be willing to just hook up their scanner (not code reader) and pull up those numbers – it’s not a Honda specific thing, any generic OBD-2 scanner can read these.

[FabioB92]

I use the torque app on my phone as a scanner and i can access PID but im not sure if what im readin is correct and what it should be. LTFT and STFT change dramatically , 7 to 14 average. Today i noticed while drivin with the scanner that if i put it into D3 my fuel trim went down drastically down to 0 and even down to-3. my o2 does shift for .2 to.8 volts but its not smooth, torque scanner has the line graph feature. if you would like to know what parts i replaced just says so, and i just put a full exhaust system on it this past weekend. It has seemed to make the gas mileage ever worse but i have been having the problem for the past year, ill post how many mpgs i get once i go through this tank and i dont think its gunna take ever long till its gone. And thanks to everyone who helps because i really dont want to get rid of the car but its just gettin way to expensive to drive.

[dreamer2355]

What is your LTFT? The STFT will always change.

[Trcustoms719]

So.., you saying your LTFT was 14??
If so that is to high, you want to see + or – 10.

[FabioB92]

Eric what do you mean communication problems, like tje ecu is faulty? Ok so first I replaced both o2 sensors ,I’m running manual spec plugs, I changed the pump and filter, cleaned egr port in manifold and replaced the valve, I have thoroughly searched for vaccuum leak but have not found one , like I said before I just put a full exhaust system on and got a new catalytic converter, and I have also seafoamed a few times. I’m going to try and pull my plugs tonight and i will post a description. Also I always torque the plugs correctly, and does anyone thinks it has to do with my valves maybe they need adjusted?

[Trcustoms719]

Quoted From FabioB92:

Eric what do you mean communication problems, like tje ecu is faulty? Ok so first I replaced both o2 sensors ,I’m running manual spec plugs, I changed the pump and filter, cleaned egr port in manifold and replaced the valve, I have thoroughly searched for vaccuum leak but have not found one , like I said before I just put a full exhaust system on and got a new catalytic converter, and I have also seafoamed a few times. I’m going to try and pull my plugs tonight and i will post a description. Also I always torque the plugs correctly, and does anyone thinks it has to do with my valves maybe they need adjusted?

What is your LTFT? That is what I’m not understanding.
+ or – 10% is ok, anything more then that would be an issue.

[dreamer2355]

Communication issues regarding your first post, not with the PCM.

Let us know how those plugs look and +1 with Eric’s post.

[FabioB92]

ok so i watched my scanner on the drive home from school and with the car in D3 LTFT was 4 STFT was 3 and bank one and two fluctuated, got home pulled the plugs they looked fairly clean and the gaps where to spec. I decided to put my short ram air intake back on so after that took the car for a drive and the scanner was showing STFT 12 and my o2 voltages are not smooth on the graph ? also i would really like to know if my valve adjustment would come into play on this?

[dreamer2355]

Your pre-cat o2 voltages are supposed to fluctuate between 0.1 and 0.9 volts.

Here is a video Eric made on 02 sensors –

http://www.youtube.com/watch?v=NIzcztO- … t3EVppbf88

As for your STFT changing with the aftermarket intake, it is because the PCM is adjusting for the additional air entering the engine.

Did you ever check your tire pressures?

Also, what are your driving habits like?

There is a few other items you can check that could affect your gas mileage. Id be looking at your coolant temperature and making sure your engine is getting up to engine temperature as quick as possible. Id be looking at ECT data as well as ensuring your using the correct viscosity oil.

Keep us posted.

[Author]

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