Hello first post here. Picked up an unmodified 2003 Evo VII a few months back. Car has 74k miles and not a hint that it was ever modded. The issue I am having is the idle is rough. It does not seek or die out. It stays consistent at 950 rpms and feels slightly lumpy almost as if there is a miss. When the AC is turned on however you can feel the vibes much stronger.

What I have done -

Cleaned MAF
Changed spark plugs
Cleaned IACV and checked function.
Checked TB for carbon buildup and function.
Checked for boost leaks (did not test with a leak tester).

Where should I go from here? Car runs fine otherwise. Pulls hard and keeps up with cars it should. Seems like no power loss. Just a lumpy idle that is a little high.

 

Any codes? Air in the coolant?

 

what does the idle sound like? are you sure it was never modded?

 

video? because i have similar symtoms. the conclusion(so far) is that the car has cams.

 

+1 cams.

 

i was thinking cams too. and now a days, people are pretty good at making a car look like it was never modded

 

^^Agree with everyone else, check for after market cams

Any noises? like air leaking?

I had a rough idle a lil while ago and it ended up being a torn o ring from the injectors

 

Popped a Random Misfire once out of about 5k miles. I don't think there is air in the coolant. How would that effect the idle?

 

The bolts on most things looked like they were never hit with a socket or wrench. The clutch is stock and still working. No indications anywhere of the normal signs of modification.

 

Its not cams. It doesn't have that pulsating "lub lub lub" idle. Just vibrates and sits at 950rpm. I don't here anything abnormal but I suppose I should do a legitimate boost leak test.

Also the car showed 145 psi across all cylinders so its likely not a head issue.

 

you should record a video might help

 

when it said random misfire, what was the code? the last number means a lot

 

my car does the exact same, it runs awesome doesnt lack performance or anything but at a stop light it has a slight hesitation like its cammed when its not, took it to my tuner and he said theres nothing wrong with it n that some cars just act like that. So unless its totally unbarable or its lacking performance i wouldnt worry too much about it

 

Try replacing the MAF. I had a similar issue on mine and the MAF was the culprit.

 

+1 on that^, this has happend to me many of times, or vacuum leak? theres alot of dumb vacuum lines for the EGR system behind intake manifold. air in coolant will do it too. and MAFs are spendy, so id try everything else first. if non of that fixes it, could be the sign of a weak fuel pump aswell, too bad you didnt have a wideband to tell us what your A/f ratio was doing

good luck