hey Guys/Gals. New to the forum new to the platform bought a 2003 Evo VIII last week and was made aware of this before hand, however its absolutely annoying and potentially dangerous to the engine. while driving the car down the highway cruising approx 75 mph 5th gear 3200ish rpm's. while just maintaining speed the car will begin to misfire. if you fully release the throttle and reapply to maintain speed or accelerate it temporarily fixes it. 2 codes set p0300 (random engine misfire) and an EGR code that i forgot the code number of. So has anyone else had a similar concern and have any suggestions on where to look first? car is mostly stock. has a turbo back exhaust, injen intake and intercooler piping, electronic boost controller and turbo timer.

 

Bump, anyone else have this issue?

 

It can be anything, you wont really know until you take the engine apart.

First thing I would do though is check/replace the coil wires, ignition coilpack and spark plugs.

 

Many people with Evo 8s have the code disabled. There is a thread devoted to it disabling the code. It is no big deal. Search p0300 disable.

Also, check your vacuum lines around the egr. They tend to pop off of not zip tied on.

 

Posted this dumbed down response in another thread recently


Do yourself a favor and search the P0300 code on here. You'll return thousands threads.

It's likely not a true misfire whatsoever. Mitsubishi's answer to the issue was drivetrain harmonics. 2-3 Rom ID changes to try and combat the issue

Disable the P0300 code routine and never worry about it again.

To add: the shutter/stumble is simply the cpu's response to the code being triggered. I have went a bit more in depth in old threads.

 

It's your input shaft bearing in the transmission. A lot of 03s have this issue including mine. I disabled the annoying misfire problem years ago but the bearing has now started to rattle around in there. Tranny rebuild is the best solution. Jacks has a new revised bearing for it too.

 

im wondering if this isnt the same problem im having except mine has not thrown a P0300 yet. i did however disable it when i cleared the codes i had which were a P0090,P0131, and a P0423.

op our symptoms sound similiar except sometimes mine will not stop misfiring at all.

https://www.evolutionm.net/forums/ev...y-problem.html

link to my thread for reference to see if symptoms sound similar.

 

So your saying the computer detects a misfire and when the p0300 sets it disables a cylinder or something which is what causes the stumble? My question now would be why does it return to normal when releasing the throttle?

 

Read through your thread, your concern sounds like it may be different than mine. Or more serve maybe. Although there was a comment in your thread that sounded similar, the guy who's car was cutting out on the highway and had a clogged fuel pump sock. Do you have to drop the tank to access the pump?

 

Drivetrain harmonics get picked up, the ECU triggers a P0300, ECUs response is what you feel. Off the gas and back on will clear up the stumble. P0300 code will remain

Like I said do yourself a favor and try one of the two ROM updates or better yet disable the code routine and never think of it again

 

no you dont have to drop the tank to access it. you pop the bottom of the back seat out and its the access panel behind the driver seat... not the one on the passenger side. i checked mine and it seems pretty clean. wouldnt hurt for you to check yours out though. its a pain to get out though because you have to be extremely careful or risk damaging the floater and then your gas gauge will read wrong.