11-03-2021, 05:32 AM
Good thinking Dave, Popgun is right; on startup the e.c.u. has no idea where the iacv position is so it opens the air valve to the end stop, now it knows the iacv's position.
The e.c.u. then looks at the engine temperature and decides how many steps to close the iacv to arrive at the correct preset value for that temperature and fuel mixture.
From memory the total amount of travel is something like 92 steps and 4 or 6 per revolution.
And during normal operation the iacv also acts on operation of the throttle akin to " assist takeoff " so it is stepping quite often.
If the piston was too far into the barrel it would re-align itself over the next few startup cycles to the position the iacv is happy with, like 2 steps forward 4 steps back, it will always find the back stop.
On a normal warm engine you can experience this iacv adjustment if you start the engine immediately after the key is switched on, the initial idle will be higher and quickly " steps down " to 1050 rpm because the iacv is still initializing.
Another thing that comes to mind is; has Gordo installed the iacv piston so the slide is aligned with the pin inside the cylinder which runs in the piston groove?
The e.c.u. then looks at the engine temperature and decides how many steps to close the iacv to arrive at the correct preset value for that temperature and fuel mixture.
From memory the total amount of travel is something like 92 steps and 4 or 6 per revolution.
And during normal operation the iacv also acts on operation of the throttle akin to " assist takeoff " so it is stepping quite often.
If the piston was too far into the barrel it would re-align itself over the next few startup cycles to the position the iacv is happy with, like 2 steps forward 4 steps back, it will always find the back stop.
On a normal warm engine you can experience this iacv adjustment if you start the engine immediately after the key is switched on, the initial idle will be higher and quickly " steps down " to 1050 rpm because the iacv is still initializing.
Another thing that comes to mind is; has Gordo installed the iacv piston so the slide is aligned with the pin inside the cylinder which runs in the piston groove?