Welcome! Becoming a registered user of ShortWingPipers.Org is free and easy! Click the "Register" link found in the upper right hand corner of this screen. It's easy and you can then join the fun posting and learning about Short Wing Pipers!

Likes Likes:  0
Results 1 to 10 of 10

Thread: engine running rough

  1. #1
    gliderman's Avatar
    Join Date
    Jan 2009
    Location
    Red Deer,AB Canada
    Posts
    1,013
    Post Thanks / Like

    Default engine running rough

    Hi All

    have a bit of a head scratch here

    PA 22-135( mine) 0-290-D2

    tried to go for a flight a couple of days ago. warmed up the engine-oil temp and pressure in the green.mag drop about 100 and even on each mag.Carb temp works properly(RPM's drop about 75-100)

    I drained all 4 sumps before flight

    lined up on the runway and applied power-used the throttle opening 2 second rule- and when the RPM's hit about 2100 it started to run rough and RPM's wouldn't increase.

    taxied back and played with mixture, carb heat, mag checked again and after a minute or so it cleared up. went for breakfast and flew back-no problems

    Took it in for it's annual today ( AME will look over my shoulder)and everything ran fine( 7 minute flight)

    however I have noticed that the engine runs a whole lot better after it is warm after I do a circuit ( increases about 100 rpm-I could have a lazy rpm gauge......

    I'm leaning toward carburation... accelerator pump....?

    any thoughts?

    Shane-o

  2. #2
    Stephen's Avatar
    Join Date
    Nov 2007
    Location
    Lopez Island, WA
    Posts
    3,171
    Post Thanks / Like

    Default Re: engine running rough

    Acceptor pump wouldn't be my first pick. Pull the plugs and inspect. Look over ignition wires for traces of shorting out, such as black marks. Check the mag timing. Run the engines at the problematic RPM and check each cylinder to see if you have a cold cylinder. Get help and open up your mags check points. Make sure all screens and filters are clear. Then get a pro to help.
    "You can only tie the record for flying low."

  3. #3

    Join Date
    May 2019
    Posts
    60
    Post Thanks / Like

    Default Re: engine running rough

    check to make sure you don't have a wet air intake filter that's being sucked into the carb venturi..... seen that do it----
    I would think the acc pump would either do a momentary flood (engine stumble with maybe or if it didn't supply extra fuel it would be slow to increase but get to full RPM.
    Might have a valve not opening all the way--- you can give it a run at the trouble rpm till hot---- then wipe each exhaust with the back end of a sharpie--- if one pipe is colder--
    it wont leave a white smear like the others. (if you don't have an IR thermometer gun)

    I should think the roughness indicates its not on every cylinder-- just one. Maybe put a new set of plugs in- in case one is cracked inside.
    I bet you will find a cold cyl. Then just narrowing it down from there. Maybe check lifters if they are Hydraulic...… sometimes they can get a chunk of crap inside
    and not reset.


    PS---- can there be a condition where the primer pump (in the cockpit) has a bad seal so when you put it into the "locked-off"
    position---- it continues to dribble fuel into the cylinder making it too rich---- ? should see a difference in the color of the
    electrode on the plug in that cylinder since it would be richer. It might be more "too rich" at low RPM than high since it would be a bigger
    %off when there is less fuel flow through the carb. I guess you could take the primer line off at the cyl and see it it is dripping.
    Not sure if this ever happens-- just an idea.....

    T
    Last edited by violinmaker; 06-22-2019 at 09:51 PM.

  4. #4
    Pacerfgoe's Avatar
    Join Date
    Nov 2009
    Location
    Close to Edmonton, Alberta
    Posts
    726
    Post Thanks / Like

    Default Re: engine running rough

    Shane.....how about carb ice, it's been quite moist in Alberta the last few weeks....
    Forrest Miller

  5. #5

    Join Date
    Dec 2015
    Posts
    372
    Post Thanks / Like

    Default Re: engine running rough

    Carb ice comes in many forms, can cause a rough running engine, or complete no running engine from smooth running, had both happen. The complete qiut was only momentary, for 1 second.. maybe only half second, but it got my attention at night over north florida, landed at lake city was 5 miles away and done for that night. Must have swallowed a huge chunk of ice all I can figure.. didnt notice any change in performance until the hiccup. Other times was a decrease in rpm along with not running quite right, apply whatever carb heat makes the engine run better.. I dont buy that all or nothing rule.. just doesnt work best at least not from my experience

  6. #6
    Administrator Steve Pierce's Avatar
    Join Date
    Nov 2007
    Location
    Graham, Texas, United States
    Posts
    11,864
    Post Thanks / Like
    Blog Entries
    1

    Default Re: engine running rough

    My experience with a faulty accelerator pump was leaking fuel past the seal and running vry rich blowing black smoke. I would check plugs under pressure as well as the ohm test. Any chance you have an exhaust valve sticking? It clears up when it gets hot makes me think that.

  7. #7

    Join Date
    May 2018
    Location
    Portland OR
    Posts
    40
    Post Thanks / Like

    Default Re: engine running rough

    Quote Originally Posted by Steve Pierce View Post
    Any chance you have an exhaust valve sticking? It clears up when it gets hot makes me think that.
    My vote with the information at hand. Sounds like morning sickness.

    Sent from my LM-X210(G) using Tapatalk

  8. #8
    gliderman's Avatar
    Join Date
    Jan 2009
    Location
    Red Deer,AB Canada
    Posts
    1,013
    Post Thanks / Like

    Default Re: engine running rough

    Quote Originally Posted by Steve Pierce View Post
    My experience with a faulty accelerator pump was leaking fuel past the seal and running vry rich blowing black smoke. I would check plugs under pressure as well as the ohm test. Any chance you have an exhaust valve sticking? It clears up when it gets hot makes me think that.
    I think you may be on to something- at the last annual we had a cylinder(1) that was low(exhaust) but cleared up after rechecking it. annual starts tomorrow- I'll let you know what we find.
    thanks all
    Shane-o

  9. #9
    Gilbert Pierce's Avatar
    Join Date
    Nov 2007
    Location
    Germantown, Tennessee 01TN
    Posts
    3,065
    Post Thanks / Like

    Default Re: engine running rough

    Quote Originally Posted by krwill View Post
    My vote with the information at hand. Sounds like morning sickness.

    Sent from my LM-X210(G) using Tapatalk
    Morning sickness.

  10. #10
    grbamford's Avatar
    Join Date
    Apr 2014
    Location
    Erie, Pa
    Posts
    218
    Post Thanks / Like
    Blog Entries
    1

    Default Re: engine running rough

    I had a similar problem a few years ago. Happened while I was taking the plane cross country from CA to VA. Turned out my #3 piston was cold. Dig around, came out that the exhaust guide valve was shot....

    Greg

Posting Permissions

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