stick valve or normal cold AM?

[Robert M. Gary]

I noticed that my Lycoming IO-360-A3B6 engine, when cold in the AM
sounds like its running on 3 cylinders for the first 5-10 seconds on
start up. After that it sounds strong and runs well. Does this sound
like "morning sickness" or just normal startup?

-Robert

[Denny]

I strongly suspect a sticking exhaust valve... This is the way it
starts with carbon/lead deposits, sticking when the valve guide is
shrunk from cold and then loosens up as the valve guide begins to
expand as the engine warms... Later, it simply stays stuck...
Get thee to a nunnery (nope, sorry, wrong thread) unuhhh, Get thee to
the autoparts store and get some Marvel Mystery Oil and add to your
gas, 8 ounces per ten gallons (continue to do that every third fill
up)... Change your oil immediately if it has more than 15 hours on it
(filter or not - and the filter does not need to be changed out for
this immediate repair), and be sure the oil has the lycoming additive,
and call Aircraft Spruce, or your favorite high priced aero parts
vendor, and have them next-day-air some AVBLEND and add it to your
oil... WIth a little luck you will head off the dreaded totally stuck
valve...

If you want ot be more proactive, pull the rocker valve covers... Pull
the top plugs... One cylinder at a time rotate the piston down out of
the way... Using a mixture of MMO and Mouse Milk in a squirt can,
drench the valve stem while using a wood block and a hammer to bounce
the exhaust valve aggressively...(MMO plus WD40 will also work in a
pinch) Reassemble the engine, doing the above gas and oil treatment,
and cross your fingers you got to it in time..

Denny

[Cockpit Colin]

I'm sure you would have noticed a sticking valve when you hand swung the
prop prior to start to check for such things ;)

"Robert M. Gary" > wrote in message
oups.com...
> I noticed that my Lycoming IO-360-A3B6 engine, when cold in the AM
> sounds like its running on 3 cylinders for the first 5-10 seconds on
> start up. After that it sounds strong and runs well. Does this sound
> like "morning sickness" or just normal startup?
>
> -Robert
>

[Brian]

Nearly every 0-235 I have flown behind does this when cold, Other
engines don't seem quite as bad but it may be that the 0-235 seem to be
ones I am usually trying to start when cold.

Often they sound like they are running on only 1 or 2 cylinders for a
few seconds.
My Pet Theory is that we often just prime them so much when
cold (often required to get them to start) that the cylinders are so
loaded up with fuel it takes a few seconds to get the fuel/air mixture
right in all the cylinders.

Another Theory is that depending upon how your primer works,
perhaps one of the cylinders is not getting primed, and it takes a few
seconds to get fuel to it.

I often start with the Carb heat on when the engine is really
cold, it obviously doesn't do much right away, but will help as soon as
any heat is available. The usuall issue I find is that the engine will
run for a few seconds and die. Reprime it and it does the same thing.
My Theory is that it may be icing up the carburator as soon as it
starts. I have also heard frosted plugs might be a possible cause. I
open to other thearys as to why the do this.


This in itself wouldn't concern me much, But I am not a mechanic. Best
to ask you Mechanic to be sure.

Brian
CFIIG/ASEL

[[email protected]]

Robert M. Gary wrote:
> I noticed that my Lycoming IO-360-A3B6 engine, when cold in the AM
> sounds like its running on 3 cylinders for the first 5-10 seconds on
> start up. After that it sounds strong and runs well. Does this sound
> like "morning sickness" or just normal startup?
>
> -Robert

sounds like a stick valve to me. once you figure out which one it is,
you need to ream the valve guide.

Frank

[Robert M. Gary]

wrote:

> sounds like a stick valve to me. once you figure out which one it is,
> you need to ream the valve guide.

I've tried to find it several times but running the EDM at startup. I
figure a sticky valve (any valve) will show a lower EGT than the other
cylinders. However, I've never been able to catch it. It doesn't happen
very often.

-Robert

[nrp]

Before shutting down, make sure your mag switch actually turns off.
On the next cold starts, hand prop it thru all the four cylinders to
see if there is a dead one.

A stuck valve won't necessarily show as low EGT. I'd actually expect
maybe a high EGT but if you say the problem is short lived (for now at
least), you might not be able to spot it with the EGT gage.

How many cylinders receive prime? Has it always done this in cold
weather?