Hi guys my fd3 has a rough idle (worse when cold) has been rebuilt with a street port any ideas on what it could be?? thanks

 

Did you check your motor mounts?

 

Yeah they were replaced with the rebuild, it doesn't die out , just idles between 1200-700ish rpm? (when cold) 1000-800rpm (warm) Changed the plugs. But above 1500rpm she idles smooth and pulls like a train all the way to the red, not loosing any water or oil, bit stuck myself??

 

Checked for vacuum leaks?

 

Whats the best way to check for these? someone said to blow into one of the intercooler pipes and listen for leaks but i thought that would ony be useful for boost leaks?

 

I had the same issue and it was one of the vacuum hoses that go to the vacuum chamber. I traced it by hearing carefully close to the UIM....

 

The "best" way to check this is block off the intake and pressurize the system with shop air. Listen for leaks, and spray soapy water if necessary. If this yields nothing you may just be running lean at idle. This will also cause idle hunting, and is usually the fault of a poorly calibrated TPS sensor.

 

i'm told its running very rich thou

 

What mods does it have?

Has it always done this?

There are a couple of good threads in the 3rd gen FAQ on checking and adjusting the idle if you haven't seen them yet.

 

It has been street ported and apexi induction kit, and blitz cat back exhaust. It hasn't always done this. But once the car is up to temp it idles a lot better, but still a little off.

 

So on a rotary engine, you do know that ports have same effects as cams..am I correct or thing wrongly here.

 

Yeah i understand that ports are like high lift cams, but i would of thought that it would be more constant and not get better when it warms up.