Idle control problem with M400

[Racingsmart]

Hello!
I use 4 wire stepper motor idle valve to control the air inlet,But I find the engine could not idle. then I take stepper motor and crank the engine , the stepper motor almost stay steady,stepper motor is not break,I don't know how should I use it control idle with M400. Thanks.

[MarkMc]

Hi,
What type of engine is it? Has the stepper motor been wired correctly?

If the engine has not been started or tuned you should not be trying to make the idle control work.

[Racingsmart]

It's a single cylinder gasoline engine,displacement is 500cc.I use injector to replace carburetor which was fixed on the engine . 4 wire marked A,B,C,D wired Aux outputs 5,6,7,8. I use starter motor to crank the engine,the TP is 0% .I think the idle control should work at this moment,but from the actual performance idle control is bad. I try to change the parameters , the effect is not marked. could you give me some advice ? Thanks!

[MarkMc]

I would be blocking off the idle control and tuning the engine to get a good idle to start with. Idle control is only to help when you have extra loads like air conditioning or power steering, maybe the alternator when the lights go on.

How does it idle without the idle control valve? If it does not idle nicely when it is up to opperating temperature without the idle control then adding an idle control valve will make things worse. You need to get the basic idle nice first.

[Racingsmart]

I block off the idle control,keep a fixed air inlet area,then I start the engine .It can idle ,but it's not very steady ,RPM is about 1100r/min when engine temperature is 30 ℃,as the temperature rising,the idle speed get higher,RPM is about 1600r/min when engine temp is 75 ℃. I want that the idle keep steady at 1300r/min,RPM change little while engine temperature change. What should I tune ? Thanks!

[MarkMc]

If you block off the idle valve and the engine idels at 1600rpm and you want it at 1300 then you have the throttle body open too much. Once the idle valve is closed there is no more the idle control can do to lower it.

You should always tune the engine when it is at opperating temperature for idle with no idle control setup. The idle tune will include the base throttle opening, fuel, and ignition, you need them all tuned correctly. Once this is done then you can start on idle control and cold start.

What is the engine used for? What vehicle? Is the stepper motor standard on this engine? The only reason I would say you need idle control is for the cold start and a simple solenoid valve would have been much better than a stepper.

[Racingsmart]

It's a small Racing car .the stepper is standard for the engine,now I block the idle control and keep the stepper valve in a fixed position , by which the engine could start .As it is ,the idle speed would change with temperature.
so I set up a fuel compensation talbe which is about RPM and ET .the RPM range from 500rpm to 1500rpm ,when the RPM exceed 1300 rpm,the fuel will reduce ,so the RPM will decrease.

In static state the idle can be steady,but the fuel is lean when I make the throttle position change ,so the load change the engine worked badly ,could you have a method to solve the problem?

a simple solenoid valve only have two state ,open and closed . when I have a cold start ,I open the solenoid valve .when the ET get high ,I close the valve.Should I use the valve like that ? Thanks!