my idle likes to go up and down and i have no idea why....
sometimes its normal and will idle around like 750-800rpm and stay there, other times its like to rev up to like 1200rpm stay there for a few seconds, then drop to about 900rpm and stay there for a few seconds, then it goes back up to 1200....

it just keeps doing that over and over, then eventually it will idle normal, but then it will do it again. whats causing this?

 

Mine is doing the same thing. Started a few weeks ago. Does yours sometimes feel like its on the verge of stalling? I have no problems throughout the rpm range, only at idle.

 

If you guys have your heater running, it's normal.

Tis the season for winter.

 

Im guessing no they dont have the heater on.. I have a fully built car and mine does this as well...

 

Just check it...maybe your ISC

https://www.evolutionm.net/forums/ev...ge-my-isc.html

 

could be there problem.. but i have a brand new throttle body and low miles on my car

 

You know, I didn't even think about the correlation to the heater being on. Don't think its the isc. Wouldn't that throw a cel?

 

Clutch switch I've read on the IX does this too. I forget where the thread is

Brand New throttle body with sensors?? I looked into a Works TB and they give you sensors but didn't know if they were brand new, maybe just reconditioned??

 

no

 

What kinda cams are installed in your car? I know when I switched out my cams it started doing something very similar to this. Tweaking the tune helped out a little bit so you could try getting in contact with your tuner to see if they can help.

 

HKS 272's have been in the car for over 40k. Its always had a lope. This is different.

 

it sounds like isc...I just had the same issue and it doesn't throw a cel

 

iscv rarely throws a code. Check your biss settings. More than likely your ISCv.

 

I had a similar issue on my 05' Evo VIII. Turned out the timing belt tensioner was installed incorrectly and the belt had slipped a tooth or two on one of the cam gears. This caused my car to have a rough idle to the point of stalling but once I was out of the idle range the car appeared to run fine.

Sounds lame but you might want to check your timing marks as just a sanity check.

 

yeah i think im getting the same problem the OP is having..
and i recently bought my evo 3 weeks ago
i think i need to get my car checked at a shop.