Engine stumble, Thoughts?

I changed my mind assuming it is a lean stumble. A low float setting
and/or possibly an obstruction in the fuel delivery system would give a
low bowl level that could make the mixture go lean enough to stumble
from the main jet. In that case it would also be running lean at full
power - not a good situation.

This still doesn't fit every symptom. The cheapest way out is to get
an EGT - and soon..

OK..some ideas here are really good thoughts.

More info..

Have EGT, reading normal, can pull mix back 30% (with normal
EGT rise) to peak, and the mix operation appears normal.

This flight was in the coldest air experienced so far with our
"new" Warrior.(we bought it in Aug) DA may have been below SL..

One thing we will check is the fuel delivery. Not too suspect
yet as the fuel pressure is good with fuel pump off, plane is
hangared, and (so far) no water has ever been sumped. I suspect a lean
stumble.. mix was fill rich when it first happened. Tried both
tanks...same.

RPM at the stumble was about 2000 - 2200 every time, no
difficulty in the 1500 range. Smoothly closing the throt (rate of full
travel to full idle 3 seconds or more ) - no prob.... quickly closing
(not yanking) caused the stumble. Recovery to smooth was 1 second.The
rate of throt travel would be about 1.5 seconds to full idle to
produce the stumble.

Engine starts on 2nd blade with proper prime, smooth and pulls strong,
burns a liter oil every 12 hours.

Thanks to all who responded! We have several learned pinions to work
with.

Dave



On 5 Dec 2005 06:23:44 -0800, "nrp" wrote:

I changed my mind assuming it is a lean stumble. A low float setting
and/or possibly an obstruction in the fuel delivery system would give a
low bowl level that could make the mixture go lean enough to stumble
from the main jet. In that case it would also be running lean at full
power - not a good situation.

This still doesn't fit every symptom. The cheapest way out is to get
an EGT - and soon..

"Dave" wrote

.. quickly closing
(not yanking) caused the stumble. Recovery to smooth was 1 second.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Man goes to the doctor and says, "doc, it hurts every time I bend my arm
back and forth real quick, like this!"

Doc says, "Then, don't do that!"

My advise? If everything runs good, in every other way, keep an eye on
everything, and "don't do that!"
--
Jim in NC