MicroSquirt.com read only forum (Jan.15,2018)

As I understand it, my MS 2.2 can't control a stepper type IAC motor. I have installed a bosch unit for fast idle. My particular throttlebody doesn't have any provision for setting or adjusting idle (warmed up) airflow other than to crack the throttle plate. The throttle plate would seem to be a crude way to set idle because I have no idea how far it should be opened.


Could I drill an opening (as I've seen on some TBs) in the throttle plate to give me the base amount of air needed at warmed up idle? If so, is there a way to determine the opening size?

It's tough to set the idle VE when I'm not even sure the airflow amount is correct.

I would not suggest modifying your throttle body, at least not by drilling a hole in it. Is there a set screw anywhere near the throttle shaft? Have you given up on adjusting your VE? I don't think you should worry about airflow amount as you call it. You should be able to generate a VE value and start to lean it out (make number smaller) in order to make it idle for now. On my previous MS-1, v2.2 I also did not have a stepper motor nor did I have a fast idle valve. I had to play with the VE until it idled well enough to adjust the timing. After that I adjusted the VE table, and finally went back and readjusted the VE value. Have you tried to advance your timing just a little at idle with the engine warmed up? I think that helped me out in the begining too.

I do have it idling. My timing is also set. I can use the TB set screw to open it far enough to get it to start. If I back that screw out to get it near proper idle speed, it will run rich but still idle. Trouble is that if I try to stop it and restart the engine at that point it'll be too rich to start and I have to open the TB back up to get it running again.

My VE tends to be a bit jumpy too. If I reduce VE at idle, the O2 sensor says I'm going lean. For example, 32 is too rich and 31 is way lean.

Any thoughts?

conn110 wrote:I do have it idling. My timing is also set. I can use the TB set screw to open it far enough to get it to start. If I back that screw out to get it near proper idle speed, it will run rich but still idle.

Cool. Stop right there and adjust the VE bins you're in for the lowest MAP. Just keep it running and ignore the O2 as it is cooling off at low load anyway. Once you have the idle at the lowest MAP number, adjust your idle speed screw (the idle speed often changes doing this) and repeat the process again. It should purr like a kitten and have instant hot restarts.

Once you have that done, you can either take an easy drive with MegaTune's Autotune running or log the drive and process it with MegaLogViewer's VE Adjust feature. You should have a tune good enough to drive to Alaska by that point. Not much heavy tweaking necessary after a few progressive runs like that - just some table smoothing and accel/decel tweaking for the most part. All that remains is cold start adjustments over the next couple days.

David