I have a evo IX with 12000 miles on it and I have noticed a rough idle when the car is fully warmed up (30+min drive).

It's not a very harsh idle like the engine is about to stall but you can hear the exhaust note miss a beat and the engine shaking/skipping more then usual (you can feel the rough idle of the engine of the cabin).

I have looked at the vacuum lines from the top of the bay and they seem like they are all put on pretty tight. Could it be a IC pipe hose that is loose?

You can also hear/feel the rough idle up to 2000rpm when the car is in neutral and i hold the rev a little. The car drives perfect and there are no CEL. The spark plugs were replaced with OEM factory ones and that didn't fix the problem, there are no mods on the car, and never was.

I'm just wondering if it could be a IC pipe that is lose, or maybe there is a vac line that is common on evos that is a bit loose. Thanks for the help.

 

I would suggest a boost leak test

 

Your stock right ?

Take it to the dealer.

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Check the vac lines on the intake manifold, they have an annoying habit of flying off because Mitsu felt it unecessary to secure them in any way.

 

I doubt you have a problem. The car idles rough stock. That is the way it is. That skip that you talk about when you hold your throttle at 2K for a about 15 sec becomes more pronounced when you put a TBE.

Do a search on rough idle and you will find multiple threads about it being normal.

 

check your fuel pump.

 

I honestly think its normal...I have a little miss now at idle and then. The only mod I have is a TB exhaust.

 

Alright thanks, I'll go through the vac lines one more time and do a boost leak test next time I bring the car back into the shop. It just worried me because the rough idle/jumping happens every 5 seconds or so when the engine is really warm, and it didn't seem normal to me. But it looks like i'm just too worried over the car. Thanks again everyone.

 

My IX has been like this since I brought it home. It feels like it skips a beat every few seconds like an old big block with a cam. I posted the same question and was told it's normal.

 

I was told it was the mivec.

 

i dont think mine does that?

 

Its alittle bit more noticeable with a TB exhaust system

 

eh normal

 

I say change your plugs.. 99% sure that will help. At least it did with my 4g63 equiped GSX when I had a rough idle.

 

Mine does that from time to time, and I have a VIII. You can feel the car trembling, but it doesn't happen at every stoplight, just comes and goes. I think it is normal.