Situation: I have a b16 turboed EK with AEM. During normal start up is fine. After a long drive on the freeway, the car start to surge 2000 rpm to 3500 rpm. I stopped the car and unplug the IACV plug and the car idle at 2000 steadily. I drive the car home and put on a new but used IACV and the car started up fine with no surges. After that, I take th car for a drive again. The same thing continues WTF. I check my TPS voltage and it's fine. I checked the Vacuum and it's also within spec. My car does not have the FITV. It's a BDL 70mm throttle body. This just drives me crazy. I have replaced the thermostat and radiator cap too. Bled all air out of the system. Have any suggestion? Can timing put it out of sequence?

 

the surges is bad when it's warm right? i have the same problem bu on a na b16

 

Yes, it surges when it is warm. Usually after 20 minutes of driving. When the motor cools down. It is okay.