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MitsuMaster, ASE Certified Technician
Category: Car
Satisfied Customers: 4
Experience:  AS. in Auto Technology, ASE Master 10 yrs, Mitsubishi Master 8 yrs, 1 yr at Toyota, 2 yrs at Ford
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Random Misfire code only at high speed

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Random Misfire code only at high speed

Hi there, hope i can help you on this one. It looked like a problem I am familiar with, and I looked it up and found that there is a technical service bulletin from mitsubishi, TSB-04-13-007 which covers both the 2003 and 2004 Lancer EVO's for a random misfire code. Unfortunately, you will have to take it to the dealer for this concern because it needs to have the ecu updated/reprogrammed. I don't know what your in service date is, but that is covered under warranty for 8 years or 80,000 miles, whichever occurs first. Let me know if you need any further help with this.




Customer: replied 6 years ago.
This problem happens when I get on the free way and hit about 70 mph. I periodically lose some power and then when I let off the gas and press it again i kind of get it back, this happens over and over at random intervals. Its frustrating. Does this sound like that tech bulletin your talking about. I just want to be sure cause I have taken it to an auto shop multiple times and they cant diagnose the problem cause they can't recreate the condition, obviously cause they can't hit 70 mph + in the garage.
From what you're describing, it sounds like its a problem with something other than the TSB, which is for incorrect parameters for the code to set. Do you have anything modified on the car?
Customer: replied 6 years ago.
Ram air intake. Sport clutch. Custom exhaust. Had the intake and exhaust for a while. Only got the clutch cause the original burned out. Got the check engine for the first time shortly after clutch replacement about 3 yrs ago with no effect on driving. Only noticed the actual performance problem about 1 yr and half later while on the freeway. Don't drive it much obviously as a result. Only 55k on it.

It is possible that something in the drive train/clutch could cause a problem like this, especially since you never had the check engine light come on before the clutch was replaced. Over time whatever was causing the code to set could have gotten progressively worse to the point where you could actually feel it. When you had the clutch replaced, did you have the original flywheel resurfaced or did you put an after market flywheel on?

Customer: replied 6 years ago.
I think the original flywheel was resurfaced. I bought a kit and had it installed. I am not sure what comes in a kit. I don't think an after market flywheel was put on. I am not sure if they come seperate. Cause if not then definitely still have the original flywheel. Cause all i paid for was the clutch/replacement.

Ok, they don't usually come in a clutch kit so we'll assume that its still the original. A few factors could cause your code to pop up, all of which are tough to single out without swapping/replacing parts. The one thing i would look at first is where the ram air intake is positioned. I have seen where they will sit in the path of the cooling fans coming on and the quick burst of hot air will cause havoc with the computer, and this might have been repositioned when the clutch was replaced. Usually coils and wires will cause individual cylinder codes to set, same as with injectors, but the MAF sensor is common to all. Check that out and let me know if that helps. Also, do you know if it does it only when hot above 70 mph, or can you take it out cold and it will do it as well?

Customer: replied 6 years ago.
It only happens when hot above 70 mph. I can drive around town without the engine light coming on/problem happening. It sucks cause I take it to the shop and they reset the code and the car is fine until I get on the freeway and hit 70+. The intake is at the upper right corner of engine bay. Pretty much same spot as before the clutch replacement

Another TSB with these cars is tsb-06-13-004, which describes all of your concerns as well. If the vehicle is above 167 degrees, over 60 mph, rpm over 2500 and engine load is less than 80%. Unfortunately the repair isn't cheap but is also a known problem with the EVO's, and that is to replace the input shaft in the transmission because it sees the splines on the 5th gear moving and it sees this as a misfire. In order to repair it you'll need the following 3 parts: Input shaft - MN107628, Input 5th gear - MN107624, and the input shaft seal should also be replaced which is MD746516.

Customer: replied 6 years ago.
I take this problem is not covered under warranty?

EVO's only have a 5 year, 60,000 mile powertrain warranty, so by mileage yes, time no. Mitsubishi is very strict with them and having modifications done to them, so if it was stock you might have a chance with a district rep helping you out with it, but they definitely won't since its been modified and probably not since its out by a few years as well.

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