I have this weird problem where the check engine light comes and goes .. if im at traffic it will come up and when i start driving it for a while after 3 days and take it on the highway or constant speeds it will go away. i put the scanner and comes up as random cylinder misfire. really weird, has anybody have this problem before?

 

At least in a 9 you only get a light. In my 8 the computer would start shutting off fuel to various cylinders, looking for the misfiring cylinder, and continue to do that off and on until the code was erased. Until erased you had a three cylinder car. This problem would invariably occur when I was 200 miles from home.

In the early 8's almost a universal problem. The fix there was to delete the periphery bit for that test. For a 9, supposedly fixed by the maker so maybe a real problem.

 

Common issue with these cars. Search P0300 on here, way more info than you can consume in a week. You'll get posts all the way back to 2003 when the EVO hit US shores

 

Mitsubishi offered 2 ROM updates for the P0300 issue on the Early VIII's. Fixed some, not all. Their diagnosis was drivetrain harmonics causing the CEL to trigger and the car would sputter. Off the gas on the gas and the car runs fine again. CEL will remain.

Yes the code would come up prior to the car sputtering and fueling like mad. Not the other way around. Thats how the car would react to the code being triggered.

Other factors may include plugs, wires, coils, too much timing idle in idle cells, large jumps in timing in the ignition map, etc...

Once yo've ruled out any ingnition or tuning related issue. For the problematic cars, just disable the code routine in the ECU and never worry about it again

 

Whats wierd is that my car drives perfect. no issues. have aggressive cams though. sometimes when i start my car it acts like it wants to shut back off but the rpms climb back up. and my engine mounts are pretty stiff. so that dosent help either.

 

The computer watches the crank sensor signal for variations in crank speed. When it detects a variation this is interpreted as misfire. If it can identify one certain cylinder, a code for that cylinder is set (P0301 thru P0304). Otherwise the general P0300 code is set.

 

I only encountered misbehaviour when the computer kept doing the self test for the misfiring cylinder. I'm not sure when this test was removed but the later cars don't do it.