Subaru throttle sensitivity

[teiland]

On my new machine with fuel injected 2.2 Subaru, the low speed throttle is extremely sensitive. The engine either wants to run at 700 rpm or above 1500. It takes only the slightest of movement in this band to speed up or slow down.

I have tried adjusting the throttle stop. When I get it set to idle at say 1100, I can go fly and next thing I know it is idling at 1700.

Can anyone offer any advise on this????

Thanks.

[david holmes]

try a stronger throttle return spring

[rfi]

There is a switch in the throttle position sensor that closes when the throttle is totally closed. The switch closure signals the ECU to take control of the idle via the idle air control valve and the idle will remain at 1000 rpm or less.

If you have played with the idle screw the switch may never close and the idle will be very erratic and the engine will not idle below about 1500 rpm.

[teiland]

Hi Don, thanks for the help here. I can readjust the stop and get back to the idle speed of 700 or so, without problem. I guess you are saying that it is best to not fool with the stop. Am I correct that there is not much you can do as to this characteristic?

David, I don't think it is a spring issue (unlike my carb'd engine). Like Don says, there is more going on here than I understand, and it certainly doesn't act at all like adjusting the idle speed on a carb.

[rfi]

David Holmes is right--the return spring could be too weak but it nomally isn't if you are using the stock setup. If the spring is weak it may not be pulling the throttle linkage all the way to the throttle stop. The butterfly valve will be almost closed but the switch won't be activated and that will cause the engine to die.

Another scenario is that the switch doesn't open soon enough and the ECU is controlling idle by closing the bypass air valve more. When the switch does open the Rpm jumps a few hundred. The switch needs to be closed at the same time that the butterfly closes completely. If the throttle position sensor is set up properly that will be the case.

[teiland]

Don, my springs are definitely pulling all the way to the stop…………….I was flying this morning with one of my students who is an auto repair shop owner, and he told me the same thing your are saying as to the throttle position sensor. I will work on that. Thanks again for your advice..

[Harry_S.]

Don P.: Don't ever leave us!!!

[KenSandyEggo]

What's weird is that I have an after-market FI on my 2.2 and it is entirely mechanical...no sensors or brain of any kind (the FI, not me!). I have the same thing; the throttle is extremely sensitive at the lower range and hard to adjust easily with the throttle.