Idle

[llebhsoj]

Hello, my m20c idles at about 500rpm when cold and when warm (trying to land) it won’t go lower than 1100 rpm. Does anyone have any ideas why and or how to fix it?  

Thank you. 

[jetdriven]

as the plane slows, the prop loads down to the normal idle speed. 1100 RPM as you are flaring is normal, becauase the airplane is windmilling the prop.

[llebhsoj]

I guess I explained it wrong. I meant that once I land and am taxiing, the lowest idle I can get is 1100 rpm.  With the power pulled all the way out there is still more power than I want when landing.  It hasn’t always been that way and my mechanic has no explanation. It’s caused me a few go arounds because it’s Wearing out my brakes. 

[Hank]

  On 8/23/2019 at 3:56 AM, llebhsoj said:

I guess I explained it wrong. I meant that once I land and am taxiing, the lowest idle I can get is 1100 rpm.  With the power pulled all the way out there is still more power than I want when landing.  It hasn’t always been that way and my mechanic has no explanation. It’s caused me a few go arounds because it’s Wearing out my brakes. 

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Wheels down, good directional control. Reach out a finger and raise the flaps, then lean the mixture--I generally go about 2/3 to Idle / Cut Off. But you need to have the Idle Adjustment checked.

[carusoam]

Josh,

It’s wearing on my internal calmness.... 

There is a thread of somebody reporting a similar idle speed issue... yesterday...

Normal idle speed is probably less than 700rpm with the throttle pulled back...

Do you have FF or MP data to corroborate the rpm reading?

 

So...

Be on the look out for what is allowing the rpm to soar...

Sounds like a loss of throttle control... 

With the engine off...

Have somebody operate the throttle control while you take a video of what is working and not.... at the engine end...

 

You will probably see where the control is binding, near the end of the throttle cable...

 

You could expect an rpm gauge to be failing, but the plane would land in a normal fashion...

at 1100rpm you can be landing a mile away...

At idle, the FF and mixture are typically in excess of what is needed, just the airflow isn’t being throttled normally.

You want to identify what is not working before flying it again... to make sure something doesn’t fall off or bind up in a really unexpected way, when you need it...

PP thoughts only, not a mechanic...

Best regards,

-a-

[PT20J]

Ignore the cold idle speed. With the engine warm, set the idle speed and mixture to spec (I don't have a C S&M manual, but it should be about 650 rpm and 25-50 rpm rise when slowly pulling mixture back just before ICO). 

Skip

[FloridaMan]

1100 RPM for a warm idle and you’ll be using up a ton of runway. I consider that to be a safety issue. 

[jaylw314]

  On 8/23/2019 at 3:56 AM, llebhsoj said:

I guess I explained it wrong. I meant that once I land and am taxiing, the lowest idle I can get is 1100 rpm.  With the power pulled all the way out there is still more power than I want when landing.  It hasn’t always been that way and my mechanic has no explanation. It’s caused me a few go arounds because it’s Wearing out my brakes. 

Expand  

Intake system leak??

If the motor still idles smoothly, it may be before the intake system splits up to each cylinder?

Edited August 26, 2019 by jaylw314

[Shiny moose]

As stated prior. Make sure your throttle is reaching the idle screw, no binding in cable, not moving in the clamps, have intake reviewed for any leaking, ensure mag timing in correct, then have your idle and mixture set 700-750 when warm to normal temps.

 landing with 1000 rpm will result in a very flat extremely long landing and probably a non flaring 3 pointer and could result in a nosewheel bounce, it you try and force it down. Just remember each knot above proper landing speeds equals 100 foot of additional  runway needed

My .02 is this is a non flying airplane until repaired