multiple misfire

hi im new to this site and the whole forum thing but i hope someone can help me out. I have a 2000 eclipse GS and im getting a trouble code reading of multiple misfire. A couple weeks ago i filled up the tank and then the car started running bad. It bucks and bogs down at low rpms but in high revs its fine. Once im at highway speed and lite on the throttle it continues to buck, but if i accelerate more it stops. I have been asking so many people what it could be but no one knows. so far i tried dry gas and new plugs and cleaning all the connections for the coil packs and the injectors but nothing worked. If anyone can give me a hint to what it might be it would be greatly appreciated.

what type of gas did you put in? What octane did you use? Did you add anything extra to the tank? Did you get the gas from a reputable gas station? Did the day you get the gas they re-fill the tank? Is it possible that you washed the engine bay?? When did you last change your air filter, and is your OEM intake system intact.



First, try Seafoam Fuel injection system cleaner. Use 1 can of Seafoam to every half tank of gas, if in doubt, get an extra one, it will not hurt to run too much of it, but it wont' help you and you'll have to do it again if you don't get enough. Do not exceed two doses of Seafoam. If it continues to act funny, pull the fuel pump, make sure the connection is intact, and that the strainer on the Fuel pump is not impaired. If there is lots of brown nasty rust stuff on the strainer, then you got gas the day they probably refilled at the station since it tends to accumulate at the bottom of the fill tank, it can get pushed into your car when you refilled. If you find lots of brown stuff on the fuel strainer, you've got a dilemma because you will need to run fuel out of the system before the fuel rail and out into a container so it doesn't get caught in the fuel rail. You may also findi t necessary to pull the fuel rail and clean it out manually as well. I recommend when cleaning the fuel rail, that you could use water if you find fuel too expensive, then rinse with alcohol, let dry and reassemble.

3rd generation eclipses DO NOT HAVE a fuel filter external from the tank. So any and all stuff that is in the gas that doesn't get caught by the strainer will end up running through the rest of the system. I do recommend fuel injection cleaner like SEAFOAM or a similar quality cleaner (Chevron Techron, or Lucas Fuel injection cleaner) be run regularly to prevent problems.

If this continues to not work then check your fuel pressure and your fuel pressure regulator. If the regulator isn't functioning properly or regulating fuel (more or less letting the pressure become too high), it will only ever run better at WOT and and less than that will not allow proper flow. Seeing as how i've not heard of too many failing though, I wouldn't bet on it.

Clean it first, and go from there.

I filled up with regular, I have been goin to the same gas station for pretty much a year and this is the first time it happened. It was also the first time I noticed that there was a sign saying 10% ethanoyl mixed. After i filled it up i added a bottle of STP fuel injector cleaner. Since then and now at half tank i put in 2 bottles of dry gas. Should i really put another bottle of cleaner in, will it hurt? just asking because you said not to exceed 2 doses. I didnt wash the engine bay and im not sure if they just refilled the station. I dont have a stock air intake, I have an Injen intake, and i just cleaned the filter in December. I also have not been using the car that much since December. I found out about the fuel filter awhile ago, I think its ridiculous that they never had one on from the factory. I will try the seafoam first and go from there. Thanks for the help, and the quick response.

Sound like its just a bad batch of gas.

other fuel injector cleaners i'm unsure of, I do know that Seafoam will straighten up most of your fuel needs from removing moisture from bad gas, to octane boosting, to cleaning your injectors. It's a highly recommended fuel system treatment. I might also mention it is petroleum based, and will work better than "dry gas" or "heet". I dont' necessarily suggest STP, i'm not saying they are bad, I just have no experience with how it reacts with fuel, what it will improve, or that it necessarily aids with cleaning.

I do know that a bad tank of gas will wreak havoc, and that the ethanol blend isn't recommended for use in most mitsubishi vehicles and will cause all kinds of problems. I run 93 octane, and it doesn't look like ethanol has reached it yet. When it does, well... hopefully the communist government doesn't mandate ALL fuels add ethanol since a fair number of vehicles perform very poorly even with a small blend.

My RS ran fine on the low grade 10% mix.
IDK about the V6 though.

Thanks again for all the help.