nickthemadpig

okay so I have an Evolution 8 2003 and I would really appreciate some help from you.

Mods:
hks 272 cams
bigger fmic
different charge piping
electric boost controller
hks ssq bov super annoying
Cameron from camtuning.com tuned vehicle it is at 331 awhp and 356 tq


The problem is I have a random multiple cylinder misfire code P0300 and sometimes but rarely get a P0420 code which is catalyst below efficiency threshold and when I am driving the car and I take it out of gear and let the car idle the rpm drops to right at 200 then it shoots to 1000 then drops again but not quite as low I would say about 250-300 then goes back to 1000 and idles fine sometimes but rarely this will cause the car to stall this results in stalling more often if the AC or heater is on the misfire is most noticeable when the car is dead cold once it heats up a little bit the misfire goes away completely most of the time except for tonight i was driving down the freeway at 65 mph and all of a sudden the car started misfiring like crazy it was not random it was like one cylinder stopped firing completely so i was pulling over and right when i got to a point where it was safe to slow down it stopped then ran fine all the way home which was 5 miles down the freeway

I have checked all over for boost leaks and vacuum leaks and I know the P0420 code could translate to a bad o2 sensor which could be causing the whole thing but when I data log it looks like it is working correct I don't know what else to look for or how else to diagnose this issue please help me

obguilliams

iTrader: (4)

Your missfire code is a common problem with the 2003 evo's. It's the input shaft bearing of the transmission which is not designed very well from the factory and starts to rattle after the bearings crush. The sensor reads it as a misfire from the vibrations and causes the car to go into limp mode around those speeds. Very irritating but there is a temporary fix. Search p0300 fix for the ecu. Pm me for directions specifically fixing it. My 5th gear rattles like crazy now and at 146k miles it's time to rebuild it and fix the problem. Jacks transmissions designed a new bearing for the problem.

For your idle problem try clean your maf sensor with electrical cleaner. They can get dirty after a while and the car won't run very well.

Hope that all helps!