got 2003 evo. engine cuts out when I stop at the light. engine behave normally when cool then idles erratically and die out after being run for a while. notice that the engine emit black smoke and misses when it idles erratically and also the idle get better when I close the blow out valve with my hand. help thanks

 

you, good sir, got a vacuum leak somewhere.

 

Are you venting your BOV or recirculating it? If you are still running a MAF then you need to recirculate it. That sounds like what your problem is.

 

^ this x2. And unless you're tuned for it and running speed density... The BOV is not a good idea, for the reasons smittyPNW said.

 

^ This or, maybe a f%^&ed up BOV. Sounds like you are VTA, make sure you are tuned for it. if not, put it back on recirc and see if the problem persists. if it does, then try a new BOV, if that dont work then.... take it to a reputable evo shop.

 

Also check for bad IACV.

 

With the '03 models the IACV is a known problem causing erratic idle. I would start there. It's on the backside of the throttle body. Mine went out around 50k miles.

 

i have around 75k miles on my car and not a problem yet.... i should change it too haha just in case.

 

thank you for all the reply. check my BOV and found that it is cyling even. at idle. adjusted the bov and it seem to work fine. I will try to put it back to recirc asap to avoid more problem . thank you again.