Hello MacB,

Since you are running Speed-Density not Alpha-N, the idle valve does not affect mixture much at all (since the extra air reducement will be compensated by MAP diff). It does however affect engine RPM, that most likely the effect you are noticing.

My suggestion would be to leave it at its default setting of 10seconds. That works the most seamless for most setups.

If you want to fully disable this behavior, set 255s this (undocumented) setting fully disables the overclose (slowly) behavior.

Best regards,

Dave

IAC is in my case a solonoid valve bypassing the air aroound the throttle plate:
https://www.boschautoparts.com/en/auto/throttle-devices/iac-valves
So if it changes under throttle (TPS > 1%) it changes the mixture affecting the VE

Hi Dave,

thx for your answers.
Regarding IAC: i was not aware of that feature, max setting is 255s which is not fully disabling this feature but should be good enough.
Today i tried \"follow TPS\" which is at least reproducible behaviour without any time-based changes like above.
What is the best setting ? My guess is that the stock setup just keeps the IAC steady at reference curve when not in idle ?

Regarding the TPS:
- all sensor grounds connected in one place like defined (have to check wiring to TPS)
- will check wiring for resistance
- sensor is almost new, should be OK
- regarding cap, any suggestions on capacity figures/spec ?

Thx
Marcus

Hello MacB,

The IAC position changes because you went out of idle mode and Iac Close delay is expired (= configured 0 in your config), see http://vems.hu/vt/help/v3/v3_idle_pwm_hardware.html.

There is no way in software to filter TPS signal, but you could add some hardware filtering if its really needed (by placing a small capacitor on the TPS signal going into v3). That said, usually when TPS signal is oscillating slightly like yours, it boils down to one of these causes:

1) there is some grounding problem somewhere in sensor ground.
2) there is too much load on the 5v signal feeding the TPS sensor causing regulator to chop (which is mirrored in the TPS)
3) the TPS sensor itself is dodgy, when tps sensors get older the runner tends to erode the ceramic resistor in the part throttle area causing a bad-ish connection there.

My advice would be to diagnose these first. Applying a cap might mask any of these problems and avoid you from fixing the root cause, which might result in bigger problems later.

I hope this answers yours questions,

Best regards,


Dave