I have a 2003 Mitsubishi Evo 8. Well my problem is that when I am driving down the interstate or over 60mph it will develop a misfire. Then when I let out of the gas it corrects the problem but it won't do it again until a little more ways down the road. Now if I am going under 60 mph it will never do it. It also won't do it if I am at WOT. I have changed the spark plugs thinking it was the problem but it wasn't. Could it be a coil going bad? I took it to the local Advance Auto and checked my service engine light and its showing 2nd O2 heater exchange code and also a multiple cylinder misfire code. It doesn't say which cylinder. If someone could please give me some insight on this just let me know. Thanks.

List of mods:
-Buschur Racing Intercooler piping
-Buschur Racing Air Intake
-ECU Flash
-255 Walbro Fuel Pump
-272 HKS Intake/exhaust Cams
-3" Perrin Tubro-back exhaust
-Equal Length exhaust manifold

 

maybe its a burnt O2?

 

a burn 02 wont make it misfire from what i know since my 02 sensor was f'ed up for a while..... change you spark plugs to bpr8es and gap them to .022-.024.....let us know what happens from there

 

I already changed them and gapped them no help...i also did the CEL fix and no help there. What else could it be? I talked to Dan at Batleground and he even said he wasn't to sure what it was.

 

It could be a coil, but usually it gets really bad really quick, especially when you try to go wot, it will drop out a cyl. or 2. Both times it happened to me, it was like 20-30min of driving, from the car being fine, to not driving. I heard from BR and AMS that 05+ coils are a little more reliable than 03's. I bought 06 coils from the dealer and havent had any problems yet...

do you actually FEEL the car misfire when you are driving? Or do you just get the cel that says you are misfiring?

 

exchange the coils with someone else to see if that's the problem. It's not your rear o2 sensor for sure. It wouldn't be a bad idea to change the front one though. If that doesn't work maybe "creader" will alleviate your problems if it keeps misfiring randomly.

 

Yea when I am going down the road at 60+ it will act like it just drops a cyl. I can feel the car vibrating and sputtering. I have a narrowband air/fuel gauge and when the car acts up the gauge shows it leaning out really bad. I know I need a wideband but I don't have the option right now. I also thought it could be the coils. I need to swap them out and see if that works.

 

The car has progressively gotten worse since it's started acting up. Now I can't hardly ever go over 60 without it misfiring. It's wierd cause it acts like it does it randomly.

 

Sounds like a p0300 code to me. Look for disable p0300 test in the ecuflash section it solved my problem.

 

How far are you from Columbus player?
Id be willing to look at it for you

 

did you read his response to my last question? Its not just a p0300 code, the car is actually dropping a cyl. while driving.

Your coils may be going out. Swap them out and drop some new plugs in there, see what happens.

 

I read the op first post and responded to him. I am glad you know everything. I will stop attempting to help people since you have all the answers.

I have had the same thing happen btwn 60-80mph at light cruise on the highway the car became undriveable because of this. It felt like it was droping a cylinder until I let my foot off the gas and then everything felt ok again. This would happen all the time. If you lose a cylinder I doubt that it would only happen on the highway at 60mph+. A p0300 code cuts timing and fuel to "save the engine" from a miss fire. It causes the whole car to make a engine brake noise, lose power, and afr to sky rocket, until you let off the gas for a split second. I would try that first instead of throwing money at coils until it is nessecary. If you want to check you coils pull one out throw an extra spark plug in there and touch it to a safe ground while a friend turns (once/twice not holding it) over the car that will tell you if they are working or not. Good luck with the misfire.

 

What cel fix did you do. I have a 03 evo 8 with the mods in my sig. I did the p0300 disable and have not had it since.

 

I did the cheap way by going and buying the non-foulers from a parts store and drilling one out with a 1/2" drill bit and screw them into each other then attaching them to the o2 and exhaust. I don't live anywhere near a shop that can look at my car computer wise. I don't have the tools to do myself.



I am almost 4 hrs. from Columbus Georgia. It's quite a long drive for me.