Cure for fouled plugs
IOANNIS A PAPAZAFIROPOULOS
: If my Cessna 172 engine is misfiring during runup, I was told by one
: person to lean it as much as possible and increase throttle
: to 2000 RPM for a few seconds. He said
: this would burn off whatever may be on the plug. I spoke
: to someone else who said that this was harmful to the engine
: since I was overheating the whole engine, not just the
: spark gap. Any comments?
: --
: -------------------------------------------------------------
: Joe Pastorek
: al...@detroit.freenet.org (little A, little L, number 1)
: -------------------------------------------------------------
This is the procedure I was taught, and I use, for both 152s and 172s,
it takes but a few seconds and it usually does the trick. I would think
that it does no harm to the engine unless it is done for a very long
period of time.
John Papazafiropoulos NASA Fellow
Aviation Institute
University of Nebraska at Omaha
Joe Pastorek
John Stephens
You won't hurt the engine this way -- you are nowhere near even
75% power, which is the usual "recommended maximum" for leaning,
and even that is only to prevent detonation. You are most
unlikely to get detonation at 2000 rpm during a static runup.
You will not "heat up the whole engine" to any appreciable
extent, either. Try it this way:
Throttle to 2000 rpm, full rich. Lean out to peak rpm (may go up
to 2100) -- back off if any roughness encountered, until smooth.
Hold that way for about 15 seconds.
Go full rich and reduce rpms to runup setting. If not smooth,
then redo this once more, for up to 30 seconds. If still not
smooth, then taxi back to the hangar and have someone change the
plugs, or clean them, or whatever.
******************************************************************
* . *
* John Stephens ._______|_______. Montgomery County Airpark *
* COMM-ASEL \(*)/ ( GAI ) *
* C-172P N51078 o/ \o Gaithersburg, Maryland *
* *
******************************************************************
Learn from the mistakes of others...
You won't live long enough to make them all yourself!
Ron Natalie
: That's what I do when I get a misfire, and 90% of the time it clears up
: the problem. The other 10%, I head back to the ramp if I can't clear it
: up after a couple minutes of the lean mixture and high power setting.
: (You may want to go a bit higher than 2000 RPM; it depends on the
: airplane. 2000-2100 sounds about right for a 172.)
Yep, and if you give the mixture a couple of turns towards lean right
after start, you might prevent the problem to begin with. In Colorado,
this was even on our checklists.
-Ron
patterson,george r
>If my Cessna 172 engine is misfiring during runup, I was told by one
>person to lean it as much as possible and increase throttle
>to 2000 RPM for a few seconds. He said
>this would burn off whatever may be on the plug. I spoke
>to someone else who said that this was harmful to the engine
>since I was overheating the whole engine, not just the
>spark gap. Any comments?
My A&P and my IA recommend this procedure for clearing fouled plugs on
my Cessna 150. I have also seen a variant of this (1500 rpm leaned run)
recommended just before shutdown. That procedure supposedly prevents
lead fouling. I forget which magazine had that one in print.
-----------------------------------------------------------------------
|
George Patterson - | The further up the ladder you get, the harder it
| is to move without falling.
|
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Brian Graham
>
>
>
>If my Cessna 172 engine is misfiring during runup, I was told by one
>person to lean it as much as possible and increase throttle
>to 2000 RPM for a few seconds. He said
>this would burn off whatever may be on the plug. I spoke
>to someone else who said that this was harmful to the engine
>since I was overheating the whole engine, not just the
>spark gap. Any comments?
>
>-------------------------------------------------------------
>Joe Pastorek
>al...@detroit.freenet.org (little A, little L, number 1)
>-------------------------------------------------------------
I am reading a book entitled "Aircraft Engine Operating Guide" by
Kas Thomas. In it he talks out unusually large rpm drops during runup
(perhaps 200 rpm) as possible being due to fould plugs. If suspected
he recommends, (on BOTH mags) setting throttle to 2000-2100 and the
mixture leaned about a third of the way for about 10 seconds.
He advised AGAINST extended ground runups as they cause localized hot
spots under the cowling, and encourages prop erosion.
By the way, he mentions elsewhere that if your plane starts okay and
idles roughly for the first few minutes and smoothes out after only a
thorough warmup, that this is referred to as "morning sickness" and is
the first sign of sticking valves.
That's my $0.02 worth. I trust the author won't mind the plug.
Brian
--
Brian Graham . Member of CASARA Ottawa
Email: gra...@psac.com ._______|_______. (Civil Air Search
\(*)/ And Rescue Association)
o/ \o
Vince Gaston
>From: al...@detroit.freenet.org (Joe Pastorek)
>Subject: Cure for fouled plugs
>Date: 5 Apr 1995 11:41:30 GMT
>If my Cessna 172 engine is misfiring during runup, I was told by one
>person to lean it as much as possible and increase throttle
>to 2000 RPM for a few seconds. He said
>this would burn off whatever may be on the plug. I spoke
>to someone else who said that this was harmful to the engine
>since I was overheating the whole engine, not just the
>spark gap. Any comments?
Did that "someone else" want you to take off at 2000 RPM.
Think about it. You have no qualms about pulling power, doing stalls, & alot
of "normal abuse" to a O-320 engine. So whats the problem of running up @
2000 RPM.
The whole subject of avgas lead content cannot be adequately addressed in such
limited forum as this.
In general, an O-320, isn't much concern. If you want specifics contact
flight school mechanics about the do's & don'ts. Here, you'll get alot of
opinions from C-172 pilots.
Ronald James Wanttaja
Vince Gaston <gas...@netcom.com> wrote:
>In article <3ltvla$d...@detroit.freenet.org> al...@detroit.freenet.org (Joe Pastorek) writes:
>
>>If my Cessna 172 engine is misfiring during runup, I was told by one
>>person to lean it as much as possible and increase throttle
>>to 2000 RPM for a few seconds. He said
>>this would burn off whatever may be on the plug. I spoke
>>to someone else who said that this was harmful to the engine
>>since I was overheating the whole engine, not just the
>>spark gap. Any comments?
>
>Did that "someone else" want you to take off at 2000 RPM.
>Think about it. You have no qualms about pulling power, doing stalls, & alot
>of "normal abuse" to a O-320 engine. So whats the problem of running up @
>2000 RPM.
The issue was not running the engine at 2000 RPM; the issue was running
a *leaned* engine at 2000 RPM. Not quite the same. Sure, you pull
higher power during takeoff, but the engine's getting a rich enough
mixture to keep it cool and prevent detonation.
>In general, an O-320, isn't much concern. If you want specifics contact
>flight school mechanics about the do's & don'ts. Here, you'll get alot of
>opinions from C-172 pilots.
Ummm, you'll get opinions from C-172 pilots, but from C-172 *owners* as
well. As opposed to the mechanics, if the owner recommends for/against
a given procedure, he or she is actually putting their money where their
mouth is. If a Rental Commando in the FBO's pilot's lounge says "It's OK"
but a grease-spattered owner in a hangar says "Don't do it," I'm gonna
tend to go with the owner.
But is a given posting from an RC or a G-SO? Ah, that's where the fun
comes in.... :-)
Ron "I'm a Grease-Spattered Commando!" Wanttaja
want...@halcyon.com
Heiko Fricke
clean the plugs as some of you explained above, taxi at as high as possible
rpm, and clean the plugs before shutdown. That was done on C150, C172 and
a fairly new C177. Were they overly concerned about bad combustion?
Does climat play a role?
BTW: Russians do the cleaning before shutdown on their 9 cyl. M-14P
radials as well
--
o o Heiko FRICKE heiko....@ensps.u-strasbg.fr
\_/ Ecole Nationale Superieure de Physique de Strasbourg
========(-*-)======== Equipe de Recherche en Microelectronique
--\_/-- --- Intentional straight and level prohibited! ---
John Stephens
Ronald James Wanttaja <want...@coho.halcyon.com> wrote:
|> The issue was not running the engine at 2000 RPM; the issue was running
|> a *leaned* engine at 2000 RPM. Not quite the same. Sure, you pull
|> higher power during takeoff, but the engine's getting a rich enough
|> mixture to keep it cool and prevent detonation.
|>
|> >In general, an O-320, isn't much concern. If you want specifics contact
|> >flight school mechanics about the do's & don'ts. Here, you'll get alot of
|> >opinions from C-172 pilots.
|>
|> Ummm, you'll get opinions from C-172 pilots, but from C-172 *owners* as
|> well. As opposed to the mechanics, if the owner recommends for/against
|> a given procedure, he or she is actually putting their money where their
|> mouth is. If a Rental Commando in the FBO's pilot's lounge says "It's OK"
|> but a grease-spattered owner in a hangar says "Don't do it," I'm gonna
|> tend to go with the owner.
|>
|> But is a given posting from an RC or a G-SO? Ah, that's where the fun
|> comes in.... :-)
As an owner (but not necessarily grease-spattered) I am quite
happy to have renter pilots keep good old 51078's plugs clean by:
- idling at 1000-1200 rpm
- taxiing at 1000 rpm, even to the point of a little extra wear
on the brakes,
- leaning the mixture while on the ground (as long as it is not
so lean that the engine starts to run rough), and
- doing a peak-rpm-leaned runup at anywhere between 1700 and
2200 rpm (for 10-20 seconds), if problems are encountered with a
normal 1700-rpm, full rich runup.
Plugs are a lot more expensive than brakes, and a botched-up
takoff due to bad plugs is much more expensive again (not
speaking from experience -- see tagline after signature)
This is fine on a C-172, but might not be the best advice in the
world for a high-powered, shock-cooling-if-you-merely-sneeze-near-it
engine, or for a tail-dragger with marginal brakes with a
cross/tail wind.
******************************************************************
* . *
* John Stephens ._______|_______. Montgomery County Airpark *
* COMM-ASEL \(*)/ ( GAI ) *
* C-172P N51078 o/ \o Gaithersburg, Maryland *
* *
******************************************************************
Learn from the mistakes of others... you won't live long enough to
make them all yourself.
P.S. Hiya, Ron.