I've got my car to idle on the MS at a steady 950-960rpm but im struggling in getting it to idle with the valve plugged in.

Without the valve plugged in it will hold a steady idle a 950-960rpm. When i plug the valve back in though the idle will fluctuate between 900 and 1100rpm every 2-3 seconds after coming to a stop or touching the throttle.

The valve settings im using are below as recommended by reverant:



Also attached a short datalog i did. It starts with the valve plugged in and then you can see the idle becomes steady when i unplug the valve.

Any suggestions on what might be causing the unstable idle?

 

I'm on my iPhone so can't see the log, but are AFRs steady? If not that'll cause idle instability, as will if it's too lean.

if the above are good, try reducing I and P until idle is steady.

 

They seem to be quite steady with it unplugged but as soon as i plug the valve in they fluctuate with the idle.

 

Yeah so you need the AFRs to be steady as the rpms are higher/lower it's a very tricky balance I still haven't nailled it.

Set it to open loop and tune the AFRs to be consistent in-between the idle target areas I.e. 900 rpm -1200rpm

 

Too much I.

you need to retune your PID gains settings. try P-10 I-42 D-5.


and your operating the valve at an odd frequency. use 6 for the multiplier.

 

i tried pwm warmup and the afrs were still just as stable as with the valve unplugged, only in closed loop they were fluctuating

I switched back to closed loop and tried brain's settings and it seems to sit around 930-950 which is a lot better. I'l give it a try during the week from a bone cold start but its a huge improvement.

Thanks Braineack

 

There's a guide on Nutz for tuning PID as is there one in the MS manual

Both would be worth a good read