Whats Up, I Just Swapped A 98 Gsr Into My 2001 Ls. Everything Is All Gravy Except For A Damn Code 21, And An Irratic Idle. It Hops From 1000 Rpms Up To About 1500 R's. I Am Running An Obd 1 P72 Chipped Ecu, With An Obd2b To Obd 1 Conversion Harness. Right Now Everything Is Still Pretty Much Stock. I Want To Get It Running Awesome Before I Make It Go Faster. Any Help Would Be Greatly Appriciated.

 

code 21 is the VTEC solenoid valve

irratc idle could be IACV or fast idle thermo valve

 

i checked all the wiring on my vtec, its all good, the solenoid click like its suppossed to. how do i check the fast idle valve?

 

all you can do is replace it. there is really no way of checking it.

 

what about the code 21?

 

Check all your vacuum hoses and connections for leaks...vacuum leaks can cause an erratic idle. Does it still happen while the car is warm? The fast idle thermo valve only controls idle while the engine is cold. Also could be a faulty/stuck IAC valve.