Bad MPG :(

Well I have looked around and read a thing a two, but you can't search MPG or gas (to short lol). I use to get pretty close to 400 miles a tank, but my car has been getting worse and worse mpg. It is now down to 280 if I am SUPER light on the gas I can get 300. I took all the extra stuff out of my car (tools, subs ect) still no change.

Now things that could be wrong (but have been this way for awhile)

Front brake could be slightly dragging, but check every so often and it only does under hard and long braking.

I have gotten a cel 2 times for the same thing. It is the coolant temp sensor, but after a restart it never came back.

Car is due for a oil change (like 10k ago)

Blown rear struts?

I have a rough idle (been that way since I got the car) like it is misfiring, I think it might be a bad fuel pump becase its not a hard misfire (Like its hitting little fuel cuts)

My main relay is slightly bad



I plan on changing my spark plugs/oil/hooking my egr up and checking my base timing. If there is anything else I could look for or change I would be more then happy to do that. The drift season is slowing down for the next few months so I have to fix this car while I can lol.



Alright as far as spec on my car is.

timing belt/water pump
Hollowed out cat (stock muffler)
Pacesetter headers (Egr block off)
Short ram (new filter k&n)
newer plugs (stock gap)/wires(NGK)/cap/coil (msd blaster 2)/rotor/fuel filter (within 15k)
tires aired to 40psi (16x7 16lbs and 205/45)
Alignment is perfect (Just taken in)
New alternator (mine was charging at 18 volts lol)
Valves were adjusted within 10k

Any of that could be causing your bad mileage. You've probably thought of it already, but it might be time to give the car some good maintenance and love. It will be real hard to get good mileage from a neglected car. Any savings on deferred maintenance is usually cancelled out by spending on repairs and poor gas mileage.

FWIW, your rough idle could be a vacuum leak. Get a big enough leak and it will be very hard on mileage.

The coolant temperature sensor for a fuel injection car is very important, not just to warn you of an engine overheating (as I thought before), but its used to determine the quantity of fuel needed. So there you go, you could start replacing that sensor and then the other basic maintenance stuff pending.

check or change everything you listed as well as the Vac Advance. i was getting poor mileage from that. check the timing.

when your driving do you have hesitation when accelerating? if so check the condition on your O2 sensors and make sure they are in the right place when plugged in. if they have white around them something is wrong.

Alright, So I fixed just about everything (oil, egr rehooked up, fuel injector cleaner (epic btw) ect) and I got my mpg, (fill to full then refill to full and divide gals used into miles driven) I got a whooping 23mpg on mostly highway driving :( . One thing I did notice today, is that the green plugs wire had split into 2 (http://i39.photobucket.com/albums/e1...ikblurcopy.jpg)
now I am unsure if that is the thremo switch or the coolant sensor plug.

My car has a rough idle once the car warms up(feels like it misses a lot), but one time it threw a code (code 6, I know it was ect lol) and the idle was perfect. Never came back though. anyway, any ideas? anyone want to confirm what plug that is? lol


Also, Car passed CA dyno smog 3 weeks ago, and no vac leaks or anything.

Green is the thermoswitch.

I would test the ECT per p. 12-26 of the manual. It could be marginal.

I'm still thinking you have a vacuum leak. That would cause the rough idle and poor mileage. Have you done any testing for vac leaks or just assuming that it's okay because it passed smog? An EGR problem could also cause a rough idle.

Just for kicks, what were your smog results?

Ok, I went back through it again, I do have a pretty bad vac leak :/ (Damn you dr snooz! lol) I sprayed carb cleaner around the engine bay and saw that 2 of my fuel injectors are seeping and that the intake gasket looked old, so I shot it and whatda know. It started running badly. I am going to change that tonight and start looking for different fuel injectors, unless you know a good way to clean to lol

Oh my smog was

15 MPH %co2 13.1 %O2 1.7 HC 54 CO% .69 NO 772
25 MPH%co2 13.9 %O2 1.0 HC 26 CO% .66 NO 555

LOL. Yeah, I have my moments. :idea:

The injector bodies are failing and the whole injector should be replaced. If you have two leaking, the other two will be leaking shortly. If you can afford it, replace all the injectors at the same time because the seals for the fuel rail should be replaced whenever you remove it and they cost me about $40 the last time I bought them. Replace all the injectors so you only have to buy the fuel rail seals one time.

If you plan on replacing the intake gasket in a night, you might want to read up on it before starting. It's a challenging undertaking. I think the OE Honda gasket is the best intake gasket to use. The aftermarket gaskets are too thin and tear, leading to big vacuum leaks and frustrating repairs.

Let us know how it goes.

lol yeah intake manifold gasket was pretty dumb, wobble extensions and wrenches are the only way lol. I got it done in a night but not before the hard coolant line next to the air filter sprung a leak lol. I also put a new thermostat (195) in and new spark plugs gap to .043 (msd coil).

So the crappy idle didn't change, but it has way more power (go figure) and I got new mpg numbers. In only city driving also driving it hard anytime I could (0-30 real fast lol) it got 19mpg, I figured it would be bad because of the driving style (not normal lol). Then I took it on the freeway and got those numbers and it was a solid 30mpg with a truck full of tools and 3 other people in the car.

I am hoping to get a little more mpg out of it, but I am very happy now that it is getting good gas mileage again. Thanks for all the help Woooooooooo!