Hello, I have a 2001 Honda Accord LX, 2.3L V-tec. All stock, no aftermarket parts.

136,XXX miles. Bought the car at 104,000 miles.
I've done all the maintenance that's required.
Transmission was rebuilt at 134,500 miles. (By Shop with 2 year warranty/24,000 Miles)
Thermostat replaced at 110,000 miles.
Timing belt was changed at 88,000 miles. (According to previous owner of car)
Cap/rotor, air filter, spark plugs, cabin air filter, oil change, radiator flush at 136,000 miles.

I noticed the HORRIBLE gas mileage about 130,000 miles.
I usually get 360-380 miles per tank. Now i'm only pulling off 280 miles per tank!
Just the past 500 miles my car been having trouble starting. It takes a 2 times to start it up. This happen when its cold start.
It don't have trouble starting if I just recently turn off the car. Such as to go in the gas station/store. The start up is rough sometimes too!

There is NO check engine light on. The car runs smooth once its warmed up.
It does idle at like 900-1000 RPM at cold start.
Can anyone please help me figure out the problem to the gas mileage/start problem.
I don't want to take it to the dealership because they are asking $118 an hour, it takes 2-3 hrs just to "try" to find the problem. PLEASE HELP!

 

test the engine coolant temp sensor for ohms should be 2000 - 2500 cold and 180 - 250 ohms when car is completely warmed up

 

Could this actually cause the car to loose over 80-100 miles per tank though??

 

To my knowledge, the coolant temp sensor would have nothing to do with your trouble, at all. I think that only shows the engine temp on the dash cluster or the sensor to tell the fans when to kick on. Haha.

Maybe it is a fuel delivery problem, since you say it is slow starting when cold. Try this test, one the engine is cold, don't start yet, just turn the key to the "on" position to allow the fuel pump to be pressurize the fuel line to get gas to the engine quicker. You can turn the key to the "on" position once or a couple times. If it starts much quicker on a cold start, then your problem is something with the fuel delivery. Since it starts fast while it's warm/wasn't long ago since it was turned off is because the fuel line still is pressurized enough (has gas closer to the engine). Try this and report back your findings.

If priming the fuel pump (which is what is mentioned above) results in faster start up, then I don't think that problem is related to the bad mpg.

Both problems, could possbily completely different problems.

The bad MPG might be from a bad air:fuel mixture. Does your car run lean or rich? If rich, the exhaust fumes should have a gassy smell to it and possibly black smoke.

EDIT:
Wouldn't hurt to clean the fuel injectors with a cleaner additive.

 

I will check as soon as I get off work in 30 minutes. I will post the result. Thank you!

 

I just went outside on break and did exactly what you told me.
I did it a couple times before i actually started the car. Well it still don't crank up right away like it did when I first got the car. However it I didn't have to try twice.

Early this morning when I went to start my car up, I'm not sure if I let go to soon while turning my keys. Well the second try i did it a few seconds after the first try and it was kinda rough sounding/feeling. Is it because i tried again to fast after the first try? I'm unsure if its actually me letting go to soon or it actually wouldn't start the first time.

Another other suggestions?

Could my gas mileage be suffering this much because of a faulty o2 sensor?

 

If the o2 sensor was bad (or even good, which is doing it's job) the check engine light would be on.

That rough start, I don't think was because of you, still probably a air:fuel mixture problem.

Would try running a fuel injector cleaner additive through it. Might be just clogged up injectors.

What does your car idle at when warm?

Oh yeah, when you did that test I said earlier, turning the key to "on", I forgot to mention, you turn the key to the "on" position and wait for about 3-5 secs (you should hear a quiet whine noise, it is the fuel pump in the fuel tank priming, makes the whine noise for about 3 secs), try it again, then start it.

 

Ive done fuel injection clean by using the GUMOUT brand bottle. The full complete system cleaner you can buy from autozone/walmart. I actually do this every oil change (3000 Miles) Or are you speaking of going to a mechanic shop and have the do a fuel injection service? Those they say runs 60 bucks, and i hate to spend the money. It just don't seem why I would be suffering so much gas.. but then again I am no expert.

My car Idles like at 750-800 I believe when its warm. It definitely idles much smoother after it warms up a few minutes.

My Accord also does not smoke. I sniffed the muffler while the car was running, and did not smell any gas/oil burning or did i see any smoke come out.

And i've been told by a few shops that my o2 sensor could actually not be working properly but yet not throw off a code? I guess they lying?

 

Well then I am pretty sure it a part that regulates air is at fault. To me, that explains the bad gas mileage, those device regulate the air to fuel mixture and if that is off, you can end up burning up excess fuel. Any uncombusted fuel in your tail pipe (excess gas that was not burned up)?
Although I do not feel I have enough knowledge on the air system to give you good enough advice, so someone else would have to chime in.

And to my knowledge a faulty o2 sensor would always throw a check engine light/code.
Haha, and a shop will charge you around $150 for that little quick fix. I know, I had one done before I learned how to work on cars.

Also, yes I ment the cheap, $10 and under, fuel system cleaner additive, NOT the shop service. They do the same thing you just did, but for much more.


You sure your gas gauge just isn't reading right? LOL

 

Hahaha I'm definitely sure my gas gauge is working properly. Gas lights comes on, fill up and its pretty much 16 gallons I refill on, and my tank is 17.1 gallons.

Well I appreciate your advice! thanks!

 

It's pretty obvious you know nothing about cars since you don't even know what a coolant temperature sensor does so why are you even bothering to try to give out advice ?

 

Yes.

Ima leave this thread to the "pros".

 

What is your actual mpg? 280 miles per tank is meaningless.

 

280/17.1=16.4 MPG

I SHOULD be getting 23-25 in the city.

 

Check the fuel pressure regulator.

 

Are you saying the coolant temp sensor sends info to adjust the air:fuel mixture? (no sarcasm intended) Please educate me. I would like to know why you think that part would be a possibility.

I am just saying, to my knowledge, I have replaced some coolant temp sensors and they just do what I mentioned earlier.

 

There are essentially four sensors in the coolant. One is for the ecu. One is for the temperature gauge. One is for the fan switch for when the car is running. One is the fan switch for when the car is off.

The one for the ecu tells the ecu if the car is cold, if the car is warm. If the car is cold the ecu will add extra fuel to start the car since the air is more dense when the car is not warm yet. It will also tell the ecu when the car is up to operating temp for certain things to function or for the car to go into closed loop.

If the ecu thinks the car is warmed up when it isn't(engine coolant temp sensor is faulty) it won't give the car enough fuel to start the car. If the ecu thinks the car is not warmed up and it is, the ecu will pump extra fuel into the engine while it's running since the ecu will always think the car is still cold as well as for the car never going into closed loop. The ecu always gives a richer fuel mixture when the car is cold than when it is warm. This is why there is more smoke when a car starts up from a cold start than from a hot start.

That's not to say I'm saying that yours is bad, but this is something that can be ruled out very easily by checking the ect sensor for ohms.

 

Ahh, thanks for the lesson. I appreciate you explaining that to me. Don't mean to bump heads, just trying to offer some help with the little knowledge I have. I'm just a backyard DIY mechanic learning as problems come.

Never knew there were 4 coolant sensors, I only knew of 2 (thought the fan when car is on or off was one sensor and didn't know there was one for the ecu). I completely understand now why you would suggest testing it out

See ya around Manny.

 

17.1 is if your tank is bone dry. You need to fill up your tank, drive then refill, note the miles driven and the amount of gas you put back in to refill your tank. Those are your numbers to divide. Fuel Log is a, great app for mpg.

 

your starting issue sounds like your fuel system isn't holding pressure once you shut the engine off for more than a few minutes.there are 3 main things that I know will cause this.first is there is a check valve in your fuel pump that maintains your fuel pressure that can go bad,second your fuel pump regulator can go bad and third you could have a leaky injector which was my problem when i had the same issue as you're having.any of these can affect your fuel mileage also.as for testing these 3 components,check the forum or youtube.good luck to you sir.

 

Thanks for the information Danny! My car the past day just been taking longer to start up. Instead of starting up right away like it use to, now it takes a a little over a second to start. It just don't feel right.
I have one question though... Would a bad valve in the fuel pump, fuel pump regulator, or leaky injector throw off a check engine light? Or can these have problems that make my car suffer like this without check engine light?

 

Mine never threw a code.I noticed the horrible mileage and also the starting issue.It was like starting up a lawn mower that has been sitting a long time and not priming it first! it would start and run horrible(putt putt choke choke cough cough)like it was fuel starved for the first 5 to as long as 15 seconds and then when it got enough fuel,it would smooth out and idle perfectly like it was brand new off of the showroom floor! There are 2 test you can do without any tools,try this first:turn your key to the on position and listen for fuel pump to kick on(it runs for 2-3 seconds)if it does great!(our fuel pumps rarely if ever go out,it's the check valve the craps out)Do this 3-5 times in a row,turn the key/pump on wait 4-5 second then turn the key to the off position.What this will do hopefully is build up the fuel pressure and on the 5th or 6th time,go ahead and start your car.Hopefully your car starts like it should.The second thing you can do is while you car is running,pull off the vacuum hose to the fuel pressure regulator.It should cause the idle speed to raise/go up! If it stays the same or drops,then you possibly have a bad regulator.Also there should never be any fuel coming out of the regulator anywhere/ever! Other than that,you really need a fuel pressure test gauge/kit for a Honda.Also vacuum leaks can be a killer and drive you crazy! Just have a really keen eye and a bright flashlight and trace/inspect them from point A to point B.Good luck sir!

 

Thank you. I will give this a try in an hour. Afterwards I'll update what I find out. Thanks again.

 

When the fuel pressure regulator goes bad fuel will leak into the vacuum hose. Start the car and then pull the vacuum hose and smell it. If it smells like gas then it's bad.

I suppose if it's really bad, when the fuel gets sucked through the intake and into the engine it could cause flooding.