Ok, so I upgraded from an 05 Ralliart to an 05 Evo about 3 weeks ago. The Evo has been in need of some TLC. So far I've changed the air filter, plugs, timing belt, balance shaft belt, and serpentine belt.

After changing the belts I started to have some idle issues. It will idle high when cold, around 1400-2000 RPM. Then when it warms up the idle will dip low enough to sometimes stall it out.

Whenever I take the car out of gear it wants to die, idle around 1000 RPM, or dip down to a few hundred RPM stumbling a bit then recover back to 1K RPM.

I initially thought there was something wrong with the timing, so I went back through the entire procedure and it looks like when the crank is at TDC on the compression stroke of #1, both cams are about a tooth ahead of the mark on the valve cover, which I don't think is a huge deal...

Now I've also been getting a couple random codes lately as well... EGR insufficient flow, and MAP sensor circuit/performance. Both of these codes seem to come up randomly...

I've checked around for any loose vacuum lines and haven't found any. Also looked for any possible leaks in the intake path. I will be checking my IAC and BISS this evening to see what kind of shape they're in.

Any other ideas are more than welcome, I'm new to the 4G63 and still have a lot to learn about it. Thanks!

 

I found a vacuum line that was hanging loose, it went onto the underside of the TB. It doesn't seem to behave quite as bad as it did, but still died twice when taking it on a spin around the block. I haven't pulled the IAC out yet, but that's next on my list. Resetting the ECU right now to see if it helps anything.

 

I doubt that this is the cause of your idle problem but being off a tooth at the cam sprocket is a big deal. As for the idle, you may need a new ISC.

 

Well it's not an entire tooth, it's in between the mark and the next tooth, I tried my to get them dead on, but that's where the gears kept going back to. About to reconnect the battery and give it a try. If I still have an issue, the IAC/ISC is coming out.

 

Pull the passenger side wheel and find the rubber plug that gives access to the end of the crankshaft. Insert a 1/2 drive to turn the crankshaft.

 

Ok, I still had issues with the idle, so I pulled out the IAC...



Looks like I found the answer to my problem!
There's no teeth whatsoever on this thing...
On a side note, did Mitsu change the IAC design before 06? This one has the spring on it and I thought this design was only on the IX.

EDIT: Found out there aren't teeth on this particular version of IAC

 

So..... I cleaned up the IAC, and checked that it moves when the key is on. All seemed well. I put the IAC back in and everything was great the whole weekend. Then Monday morning I start up to head to work and I'm having issues again.

It seems to be the worst when it's cold. Also when coming from idle to load and back to idle quickly, like when in line at a stop sign. I'm guessing the IAC is still the culprit. Is it not opening back up fast enough when I go from engine load back to neutral? I'm not exactly sure how the IAC behaves while driving.

I know about parking the IAC and adjusting the BISS, but I do not have a cable or software to do so. Is there any other workaround for this issue? I read about someone that drilled a couple holes in his IAC to allow more airflow and that seemed to work, but any other options would be appreciated.

Also... And this kinda goes back to what I had first thought was the issue.... Is it possible that the cams and the 3-4* timing advance is causing the issue?

Another thing is that I'm sitting at about 8-12 inHg of vacuum at idle... That seems pretty low to me, but I have yet to find another loose hose.

Sorry for the scattered thoughts, but I'm running through any possible causes to this.