I have an '03 Lancer OZ, with about 79K on it. Recently it has been running poorly under acceleration. (Like it's not getting enough fuel) When I am up to speed or not accelerating that hard, it runs fine. My fuel mileage is excellent, I am getting 36-38MPG, so the tuning, timing, etc has to be good. I keep the air filter clean (I have a KN high flow) change the oil regularily, I just put new plugs in not too long ago. (did not change the coils or wires)

Do you think the fuel starvation could be just a dirty fuel filter? (It's never been changed) or the coils? or any other suggestions?

 

Are you sure that it has been just recently this is happening, because that is pretty typical of the Lancer. I don't have one, but I have read that the "Tornado" that you have can become a restriction to air flow if it is not working properly, and some feel even if it is working like it is supposed to it can restrict air flow under some accelerating situations.

Also you could check for exhaust leaks which cause you to loose backpressure and rob you of low end torque.

Could be just some bad gas as well.

 

There is no real fuel filter (that I have seen anyways). There is a nylon bag on the end of the fuel pump. I cant see that being an issue.

Do a seafoam regiment, gas, oil, intake manifold and see what happens.

 

speaking of seafoam, where the hell can i get that stuff? ive looked in autozone, advanced autoparts, even walmart, i cant find it anywhere.

 

Autozone carries it!.. If you don't see something, remember to ask someone who works there

 

GOOD LORD!!! 35-36 MPG! I used to get around 29 or so and now I am down to 25

 

Yes it only started happening a week or two ago. (as far as the accel issue.) Also there is some sort of fuel filter in the back of the car (it's $87 BTW) I don't know if I'll change that yet. I am starting to think maybe it's the extremely hot weather we've been having lately. (Dew points in the 70's and temps near 100) Maybe I was just getting vapor lock. Will have to wait till it cools off a little to see if it gets better.

I was not kidding BTW about the gas mileage. I drive mostly freeway, I use mid-grade gas (mostly from Kwik Trip) and I drive fast too. I still manage to average 36-38 MPG lately in the summer. It drops a little in the winter with colder temps, and poorer quality gas, but is still above 32MPG.

I run valvoline semi-syn oil, and valvoline higher mileage oil treatment, and also run a gas system cleaner usually every time I change the oil. Doing these few things really brought my MPG up. I was getting 29-30 before I switched to using those products.

 

You should get better gas mileage in the winter, colder air=more dense, more dense=more oxygen molecules/cubic ft, which creates more efficient fuel burn off. Since the opposite is true, then what you said about heat and humidity is true, and explains why your car is not as peppy in hot air, or when the engine is hot, which is why people put CAI's and SRI's on, to get cold air into the engine.