hey.. i'm getting really horrible gas mileage on my 03 tl-s. i've tried everything from changing tire pressures to 34 psi, replacing the purge control solenoid valve (denso), replacing the front o2 sensor (denso), adjusted the throttle cable. i've also tried using the STP fuel treatment **** but that obviously didn't work out. drained the coolant resovoir tank and put new honda coolant in. i recently seafoamed my car and i also cleaned out the intake manifold/egr ports. also cleaned the iacv as well.
-my air filter was replaced not too long ago (k&n air filter)
-my spark plugs only have 15k miles on them
-my ignition coils also have 15k miles on them
-no CEL whatsoever..
-used to have engine mods.. but now i only have the midmuffler deleted and the tsudo exhaust, which in no way should have any problems with mpg.
from what i think the problem could be but i need some confirmation:
-also.. my belt tensioner is making noises so i need a new one, but i'm sure that wouldn't fix the gas mileage problem anyways
-could be a bad CAT?
-previous owner replaced gas cap with an aftermarket one.. is that fine to use? fits perfectly.
-still need to do the 105k service, but again.. my mpg would not still be this bad
-rear o2 sensor has been previously ripped off the car when my midmuffler was removed (dumbass guy there didnt use a stand to hold the exhaust.. so my exhaust literally hung from my car once he cut the midmuffler off).. caused a CEL.. put the wires back into the connector, and no CEL on ever since. but i think that could've damaged the wires.. im getting no CEL but should i bother replacing it since the rear o2 doesn't even read air/fuel ratios
to finish everything off.. i am only getting 13mpg and i do mostly city driving. i literally watch my gas meter drop everytime i get off a red light. and trust me, i'm slammed so i don't drive fast at all, i drive like a granny. i never drive above 2.5k unless i have to (getting onto the freeway). i've literally tried everything and it's getting me pissed off to an extent that i just wanna sell this "pos".
currently.. i'm waiting for my tank to be near completely empty and i'm gonna use some gumout fuel injector cleaner to see how that works out. but i doubt like you guys said.. that it would work. this is my last resort before i let her go. i'm tired of wasting money on gas when i know i could be getting 350~ to a tank when i'm only getting barely 180-200 miles to a full tank. i also asked a local car parts dealer in my city how much it would cost for 6 new injectors that are reman(remanufactured).. and they said 39 for each.. which comes out to 234~. i don't think they'll charge tax since my buddy works there. but yeah.. really looking into replacing the injectors.
3 days ago i pumped up at chevron.. i pump 91.. and i don't cheap out on that bs. i put in 30 bucks.. got me from empty (gas light on) to halfway. at a quarter down from half, i already driven 58 miles (holy ****ing horrible). and now as the car is nearing empty.. i've only driven 70 something miles). when i am almost near empty.. i will be getting about almost 100 miles.
you guys can't feel my pain haha.. it's embarrassing killing this much gas on a v6. my buddy with a sl55 amg (v8) gets better gas mileage than me. my friend with a bmw 540i (v8) gets better gas mileage than me. so does my friend in a lexus ls400 (v8). i officially get the worse mpg on acurazine, period. and sometimes it's not funny cause if i dare to even floor the car.. i'll get 11-13mpg, no kidding.
I do better in a 200,000 mile old V8 full size pickup. Wow.
Have you checked to make sure the car rolls freely? Jack the car and try to spin the wheels (in neutral); that'll tell you if a brake is stuck or a wheel bearing has failed severely. Try putting it in neutral at speed and see how well it rolls on flat pavement in case a failed wheel bearing is only being a problem when it's bearing a load.
A bad, plugged catalytic converter would prevent you from reaching high RPM. Is it so slammed that you can't open it up and try to accelerate hard anywhere? Go give it a try. However, when my cat was clogged my fuel economy was barely affected...power sure was gone, but FE wasn't too bad.
Your evaporative emissions system won't affect your fuel economy. Don't worry about the purge solenoid or the gas cap.
You also seem concerned about cleaning the fuel system but I doubt that could be at fault.
Other than heavy modifications and severe drag, I can't imagine what would put you at 13mpg, even driving fast in all heavy city traffic. Maybe a failing MAF sensor? Even a problem with the O2 sensors shouldn't do THAT bad, just put you in open loop all the time.
I don't know much about lowering but could severe driveline angles introduce major drag?
I imagine that your concerns about valve adjustment and the belt tensioner are worth chasing.
2 items of relatively low cost worth spending for regular maintenance anyway...thermostat and fuel filter. stuck open or clogged, respectively, could affect efficiency adversely...both would REALLY hurt.