Thanks Thanks:  0
Results 1 to 8 of 8

Thread: IO-520 Low Idle and Stumbles

  1. #1
    behindpropellers's Avatar
    Join Date
    Feb 2003
    Location
    NE Ohio
    Posts
    6,552
    Post Thanks / Like

    IO-520 Low Idle and Stumbles

    Chasing this right now:

    IO-520A Rebuilt Mags and New Engine controls.

    1. Idle is low.
    2. When advancing throttle it stumbles before catching up.


    Informed guess: Previous throttle cable was adjusted to give the correct idle RPM. Fuel flow is not up to spec on the low end.

    Gauges go on the fuel system next week...

    Tim

  2. #2
    www.SkupTech.com mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    8,484
    Post Thanks / Like
    yes step one, get fuel high & low pressure correct, to high end of range on high.(well at least for sea level)

    get it to idle as low as it will stay running, if you got a good cam this can be down to ~350, you should see a little black smoke out of exhaust when mixture is correct at this low idle, not that you idle it that low always, but helps for landing..

  3. #3

    Join Date
    Nov 2012
    Posts
    3
    Post Thanks / Like
    Just just went through this on my 520. Sounds like your idle mixture is to lean. Do you get a small rise as you cut the mixer? If not, to lean. This will cause a stumble when advancing throttle from idle..
    check your high and low fuel pressure, adjust idle and idle mixture. Then you should b good..


    Quote Originally Posted by behindpropellers View Post
    Chasing this right now:

    IO-520A Rebuilt Mags and New Engine controls.

    1. Idle is low.
    2. When advancing throttle it stumbles before catching up.


    Informed guess: Previous throttle cable was adjusted to give the correct idle RPM. Fuel flow is not up to spec on the low end.

    Gauges go on the fuel system next week...

    Tim

  4. #4

    Join Date
    Oct 2006
    Location
    anchorage, alaska
    Posts
    127
    Post Thanks / Like
    If I remember correctly, the manual I have says set the rpm at 1000. Slowly pull the mixture out to almost cutoff. As you lean, the rpm shud increase about 50 rpm, then decrease. This shud give you a quick idea of how to adjust the mixture.

  5. #5

    Join Date
    Dec 2006
    Location
    Meanwhile,...
    Posts
    4,328
    Post Thanks / Like
    Clean the injectors, I use Hoppies #9 in an ultrasonic hot pot. Mine really hesitates and won’t come off idle unless you baby it if the injectors have more than say 250-300hrs since the last cleaning. Also if you are getting a little fuel drip out of the injection vent line after shut down the flow divider may need a rebuild, just had that done.
    Last edited by OLDCROWE; 11-13-2017 at 06:50 AM.
    "Don't feed the hipsters"

  6. #6
    behindpropellers's Avatar
    Join Date
    Feb 2003
    Location
    NE Ohio
    Posts
    6,552
    Post Thanks / Like
    Thanks Kirby!

  7. #7
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    7,175
    Post Thanks / Like
    Quote Originally Posted by charlesf View Post
    If I remember correctly, the manual I have says set the rpm at 1000. Slowly pull the mixture out to almost cutoff. As you lean, the rpm shud increase about 50 rpm, then decrease. This shud give you a quick idea of how to adjust the mixture.
    This is standard procedure for ALL engines for determining idle mixture setting, not just the big Continentals.
    N1PA

  8. #8
    Steve Pierce's Avatar
    Join Date
    Mar 2002
    Location
    Graham, TX
    Posts
    16,456
    Post Thanks / Like
    Quote Originally Posted by OLDCROWE View Post
    Clean the injectors, I use Hoppies #9 in an ultrasonic hot pot. Mine really hesitates and won’t come off idle unless you baby it if the injectors have more than say 250-300hrs since the last cleaning. Also if you are getting a little fuel drip out of the injection vent line after shut down the flow divider may need a rebuild, just had that done.
    Had an IO-520 in a C210 that I had to clean the injectors every 100 hours or it would hesitate like that.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

Similar Threads

  1. IO470 Idle Help
    By flyby in forum Cafe Supercub
    Replies: 16
    Last Post: 02-08-2017, 08:25 AM
  2. Initial idle mixture adjustment
    By sburg58 in forum Super Cub Sick Bay
    Replies: 1
    Last Post: 09-26-2015, 08:37 PM
  3. Throtlle goes back to flight idle on its own
    By N197BC in forum Super Cub Sick Bay
    Replies: 34
    Last Post: 06-15-2014, 07:25 PM
  4. Low idle oil press on new C90
    By a3holerman in forum Super Cub Sick Bay
    Replies: 22
    Last Post: 11-26-2007, 06:52 PM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •