Lack of power in Cessna 172-R

[Chuck]

Hi, all,

Could someone please provide some suggestions on this.

Last summer we bought a 1997 160 HP Cessna 172-R. The test flight
(with 3 adults) went just fine.

When I picked the plane up from the shop after the service (required
to fix certain things that needed it [such as a loose tail!], the
performance was very sluggish. It did not seem like the same plane -
quite underpowered.

Even below gross weight, it couldn't take off from a 2200' runway
without scaring the heck out of me thinking we weren't going to make
it. OK it was hot but the book said we should be over a 50' obstacle
at about 1800' - we were not even close!

All rpm indications were within spec (for static run-up, etc). When on
the takeoff roll, rpm was about 2100, which seemed low, but there is
no spec in the POH for rpm for the takeoff roll. The rpm went much
higher after we were cruising (2300 or so).

Also, there was a "burbling" sound from the exhaust.

The prop was removed, inspected and put back on (with pleanty of
scratch marks which weren't there before.

Any suggestions would be greatly appreciated.

TIA Chuck

Freedom Chuck - The Man of 1,000 Songs

see my website at: www.freedom-chuck.com

[Gary]

> Hi, all,
>
> Could someone please provide some suggestions on this.
>
> Last summer we bought a 1997 160 HP Cessna 172-R. The test flight
> (with 3 adults) went just fine.
>
> When I picked the plane up from the shop after the service (required
> to fix certain things that needed it [such as a loose tail!], the
> performance was very sluggish. It did not seem like the same plane -
> quite underpowered.
>
> Even below gross weight, it couldn't take off from a 2200' runway
> without scaring the heck out of me thinking we weren't going to make
> it. OK it was hot but the book said we should be over a 50' obstacle
> at about 1800' - we were not even close!
>
> All rpm indications were within spec (for static run-up, etc). When on
> the takeoff roll, rpm was about 2100, which seemed low, but there is
> no spec in the POH for rpm for the takeoff roll. The rpm went much
> higher after we were cruising (2300 or so).
>
> Also, there was a "burbling" sound from the exhaust.
>
> The prop was removed, inspected and put back on (with pleanty of
> scratch marks which weren't there before.
>
> Any suggestions would be greatly appreciated.
>
> TIA Chuck

Do a compression check on all cylinders. Find out from the factory what RPM
you ought to get on full power static runup. When you get to know an
airplane and one day it seems sluggish, it probably is and you need to
figure out why.

[No Spam]

> All rpm indications were within spec (for static run-up, etc). When on
> the takeoff roll, rpm was about 2100, which seemed low, but there is
> no spec in the POH for rpm for the takeoff roll. The rpm went much
> higher after we were cruising (2300 or so).

Look at the TCDS (3A12) and you'll find static RPM limits. Go here:
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/
EE81A0B13ADB620986256E2B0054B119?OpenDocument

Static RPM, I would think - flame on, is a pretty good indication of overall
engine health. At least it's a place to start. Only 2100 during the takeoff
roll sounds like something ain't right.

Has it been this way since last Summer?

No Spam

[Victor J. Osborne, Jr.]

Are you getting enough fuel flow/pressure?

--

Thx, {|;-)

Victor J. (Jim) Osborne, Jr.



take off my shoes to reply

[Roger Long]

If the lifters spall, become rough, and wear down the cam, there will be
almost no roughness. The engine will simply lose power as you describe. It
may make static RPM but not reach full RPM in cruise (it's a bit more
complex with a CS prop).

Oil analysis will not show the big pieces of metal that come off the lifters
and may miss the cam shaft wear as well. Have the filters been cut open and
carefully inspected at each oil change? It takes more than just a look.
They need to be drained and inspected very closely. Washing in solvent and
running a magnet around in the pail is recommended by some.

This is just one possibility but it's very much on my mind since our engine
is currently spread out on a rebuild bench.

--
Roger Long

[Aaron Coolidge]

Chuck > wrote:
: Hi, all,

Hi Chuck!

: All rpm indications were within spec (for static run-up, etc). When on
: the takeoff roll, rpm was about 2100, which seemed low, but there is
: no spec in the POH for rpm for the takeoff roll. The rpm went much
: higher after we were cruising (2300 or so).

: Also, there was a "burbling" sound from the exhaust.

There have been numerous cases of the 172R's fuel injection running
excessively rich, causing poor idle, loss of power, etc. Do ground
witnesses see a trail of black smoke from the exhaust at full power?

You might want to ask a mechanic familiar with the 172R fuel injection
about how it might be tested.

IIRC, the 172S, the 180 HP version, has a much lower incidence of this
issue.

--
Aaron Coolidge (N9376J)

[G.R. Patterson III]

Chuck wrote:
>
> Also, there was a "burbling" sound from the exhaust.

Fuel spilling in. It's running way too rich.

George Patterson
A diplomat is a person who can tell you to go to hell in such a way that
you look forward to the trip.

[Chuck]

Hi, all,
First, I want to thank everyone who made suggestions.

Gary, a compression check was done on all cylinders and the
compression is fine. The power for a full-power static runup should be
2065 to 2165 with the mixture leaned for max rpm. The actual rpm is
about 2150.

No Spam, I could not get the website you gave me. Is there an
alternative one? I agree with you, 2100 rpm on the takeoff rull seems
a bit slow, but I don't know what the norm is for this plane.

Victor J. Osborne Jr., your question about fuel flow/pressure is
interesting. When starting you are supposed to advance the lean
control with the aux. fuel pump on to get about 3-5 gal/hr., then when
it starts, you turn off the aux. fuel pump. But once the engine
starts, I don't know what the fuel flow/pressure is. Do I read it on
the fuel flow gage?

Roger Long, I don't know if your "lifters" problem applies to this
plane because the cruise is fine. Just the take off and climb out is
sluggish. Since the compression is good, I'm assuming the engine is
ok. Am I mistaken?

Aaron Coolidge, your comment about the fuel injection is also
interesting. I will certainly ask our mechanic to check it (since the
plane is in for its annual anyways). I did not, however, notice loss
of power, but at minimum rpm (with the throttle full out) it does not
idle very well -- it feel like it's going to stop.

George Patterson, you say it's running way to rich. I was wondering
way you say this, but you just may be right. To correct this I


Once again, thanks to everyone.

Chuck



Freedom Chuck - The Man of 1,000 Songs

see my website at: www.freedom-chuck.com

[Dan Thomas]

"Gary" > wrote in message >...

> >
> > Also, there was a "burbling" sound from the exhaust.

Maybe loose baffle in muffler restricting the outlet. Could have
broken loose between the time you tried it and the time you took it
away.
Other things to check might be one mag retarded somewhat, perhaps
caused by a broken impulse coupling spring.
Did you try leaning the mixture a bit to see if there was better
RPM in the static runup?

Dan

[G.R. Patterson III]

Chuck wrote:
>
> George Patterson, you say it's running way to rich. I was wondering
> way you say this, but you just may be right. To correct this I

The "burbling" sound you report is typical of raw gas going through the engine
and igniting in the exhaust system. I'm not familiar with the injector system,
so I really can't help with troubleshooting. With a carbureted engine, you
could easily check this by leaning on the ground.

George Patterson
A diplomat is a person who can tell you to go to hell in such a way that
you look forward to the trip.

[tony roberts]

> Last summer we bought a 1997 160 HP Cessna 172-R. The test flight
> (with 3 adults) went just fine.

Hi Chuck

Suggest you pull all of the plugs & examine them - I believe that you
will find at least some of them are black from running too rich.

I also suggest that you also post your question at:
http://www.cessnaowner.org/new/forum/forums.htm

There is a ton of Cessna knowledge there.

Tony


--

Tony Roberts
PP-ASEL
VFR OTT
Night
Almost Instrument :)
Cessna 172H C-GICE

[Chuck]

Hi, Dan,

Thanks for your suggestions.

I leaned the mixture for the static runup and consequently got good
results. I did NOT lean before takeoff. Perhaps that is significant.

Chuck


On 12 Feb 2004 16:57:35 -0800, (Dan
Thomas) wrote:

>"Gary" > wrote in message >...
>
>> >
>> > Also, there was a "burbling" sound from the exhaust.
>
> Maybe loose baffle in muffler restricting the outlet. Could have
>broken loose between the time you tried it and the time you took it
>away.
> Other things to check might be one mag retarded somewhat, perhaps
>caused by a broken impulse coupling spring.
> Did you try leaning the mixture a bit to see if there was better
>RPM in the static runup?
>
> Dan


Freedom Chuck - The Man of 1,000 Songs

see my website at: www.freedom-chuck.com

[Chuck]

Hi, George,

Thanks again for your help. I'm going to ask my AME to check the fuel
injection system.

Chuck


On Fri, 13 Feb 2004 01:30:35 GMT, "G.R. Patterson III"
> wrote:

>
>
>Chuck wrote:
>>
>> George Patterson, you say it's running way to rich. I was wondering
>> way you say this, but you just may be right. To correct this I
>
>The "burbling" sound you report is typical of raw gas going through the engine
>and igniting in the exhaust system. I'm not familiar with the injector system,
>so I really can't help with troubleshooting. With a carbureted engine, you
>could easily check this by leaning on the ground.
>
>George Patterson
> A diplomat is a person who can tell you to go to hell in such a way that
> you look forward to the trip.


Freedom Chuck - The Man of 1,000 Songs

see my website at: www.freedom-chuck.com

[Chuck]

Thanks for your suggestion, Tony,

I'll ask my AME to check the plugs, as well as the fuel injection
system. And I'll try the forum you suggested.

Chuck



On Fri, 13 Feb 2004 02:06:26 GMT, tony roberts >
wrote:

>
>> Last summer we bought a 1997 160 HP Cessna 172-R. The test flight
>> (with 3 adults) went just fine.
>
>Hi Chuck
>
>Suggest you pull all of the plugs & examine them - I believe that you
>will find at least some of them are black from running too rich.
>
>I also suggest that you also post your question at:
>http://www.cessnaowner.org/new/forum/forums.htm
>
>There is a ton of Cessna knowledge there.
>
>Tony


Freedom Chuck - The Man of 1,000 Songs

see my website at: www.freedom-chuck.com

[Rick Glasser]

On Fri, 13 Feb 2004, Chuck wrote:

> Victor J. Osborne Jr., your question about fuel flow/pressure is
> interesting. When starting you are supposed to advance the lean
> control with the aux. fuel pump on to get about 3-5 gal/hr., then when
> it starts, you turn off the aux. fuel pump. But once the engine
> starts, I don't know what the fuel flow/pressure is. Do I read it on
> the fuel flow gage?
>

You leave the pump on until after starting? My 172R POH says to shut the
pump off before starting. I only use the pump for priming and switching
tanks. I also make sure to lean back a few turns as soon as the engine
settles down.

--
Rick/JYO
remove 'nospam' to reply

[Victor J. Osborne, Jr.]

Re: fuel flow/pressure. I recently learned that some add-on fuel flow
transducers can restrict fuel flow, resulting in reduced flow (actually
pressure) to the injectors. i.e. you do not develop full power on take off.

Having said (?) that, I have no idea how you would check the fuel pressure
on a 172. W/o manifold pressure at sea level, I guess you w/b left w/
installing an aux. gauge for the test.

Thx, {|;-)

Victor J. (Jim) Osborne, Jr.



take off my shoes to reply

[Roger Hamlett]

"Chuck" > wrote in message
...
> Hi, all,
> First, I want to thank everyone who made suggestions.
>
> Gary, a compression check was done on all cylinders and the
> compression is fine. The power for a full-power static runup should be
> 2065 to 2165 with the mixture leaned for max rpm. The actual rpm is
> about 2150.
I think this is the most significant thing said. There is no way that the
engine should give higher revs on the static check, than on the takeoff
roll, unless something is making a 'difference' between the configuration. I
see latter, that you say you lean for the power check, but not the take-off
roll. The obvious question at this point, is what altitude the field is at?.
If it is below perhaps 3000 feet, then the difference, together with the
noise reported really solidly implies that the injection is running rich at
it's default settings. If you are higher than this, then you should really
be considering leaning for takeoff.

><snipped>
> Aaron Coolidge, your comment about the fuel injection is also
> interesting. I will certainly ask our mechanic to check it (since the
> plane is in for its annual anyways). I did not, however, notice loss
> of power, but at minimum rpm (with the throttle full out) it does not
> idle very well -- it feel like it's going to stop.
Rich...

> George Patterson, you say it's running way to rich. I was wondering
> way you say this, but you just may be right. To correct this I
>
>
> Once again, thanks to everyone.
>
> Chuck
I think George has hit the nail on the head.

Best Wishes

[Brien K. Meehan]

Chuck > wrote in message >...

> I'll ask my AME to check the plugs, as well as the fuel injection
> system. And I'll try the forum you suggested.

Wow, your AME must be pretty well-rounded. I don't think mine even
dabbles in mechanics. ;-)

[Nathan Young]

On Thu, 12 Feb 2004 19:02:46 GMT, Chuck
> wrote:

>Hi, all,
>
>All rpm indications were within spec (for static run-up, etc). When on
>the takeoff roll, rpm was about 2100, which seemed low, but there is
>no spec in the POH for rpm for the takeoff roll. The rpm went much
>higher after we were cruising (2300 or so).
>
>Also, there was a "burbling" sound from the exhaust.

>The prop was removed, inspected and put back on (with pleanty of
>scratch marks which weren't there before.
>

Are you sure they put the correct prop on the plane? I know some of
the new 172 series were produced with 160hp and others with 180hp.
Although you have to hope the mechanics did a better job - if you have
a 160hp it is possible they swapped props with a 180hp 172.

A cruise prop would drag down both the static RPM and climb
performance. On the other hand, you should notice a few mph
improvement in cruise (unless the prop is grossly wrong).

-Nathan

[Michael Nickolas]

Chuck > wrote:

>it. OK it was hot but the book said we should be over a 50' obstacle
>at about 1800' - we were not even close!

Hey Chuck,

Maybe those 1000 songs were weighing down the plane <grin>.



Michael Nickolas
www.studionineproductions.com

[Paul Sengupta]

"G.R. Patterson III" > wrote in message
...
>
>
> Chuck wrote:
> >
> > Also, there was a "burbling" sound from the exhaust.
>
> Fuel spilling in. It's running way too rich.

http://www.sumpthis.com/docketno2001ce14ad/amend3912164ad20010617rin2120aa64
..htm

or

http://makeashorterlink.com/?K66442667

Paul

[Paul Sengupta]

"Nathan Young" > wrote in message
...
> On Thu, 12 Feb 2004 19:02:46 GMT, Chuck
> > wrote:
>
> >The prop was removed, inspected and put back on (with plenty of
> >scratch marks which weren't there before.
>
> if you have
> a 160hp it is possible they swapped props with a 180hp 172.

Hah! Different prop! I'd have never have thought of that, I
can't imagine props having been swapped between aircraft!
Sounds like a good explanation given the symptoms or lack
thereof...and given that the prop came back looking different!

This should be easy to trace with the serial numbers shouldn't it?

Paul

[Russell Kent]

Chuck wrote:

> Thanks again for your help. I'm going to ask my AME to check the fuel injection
> system.

You can do what you want, but I suspect that your mechanic (A&P: Airframe and
Powerplant) would know more about the fuel injection system than your physician
(AME: Aviation Medical Examiner). :-)

Russell Kent

[Mark Bailey]

I think Roger Long could be on to something. I had a like experience
with my Hawk XP. Although it has a different engine than the "R", I
too had a power loss. Airplane would not get off the ground well and
climbed poorly. Flew a little slower, but not seemingly much. Had
the fuel system overhauled as well as the governor. No change.
Leaning had no effect. Compressions were no lower than 73. After a
couple shops, the mechanic found same issue Roger mentioned. Mechanic
replaced a few parts and the old plane was back. Good luck!


Mark

[Dan Thomas]

Russell Kent > wrote in message >...
> Chuck wrote:
>
> > Thanks again for your help. I'm going to ask my AME to check the fuel injection
> > system.
>
> You can do what you want, but I suspect that your mechanic (A&P: Airframe and
> Powerplant) would know more about the fuel injection system than your physician
> (AME: Aviation Medical Examiner). :-)
>
> Russell Kent

He'll be a Canadian. An AME here is an Aircraft Maintenance
Engineer, roughly equivalent to an A&P-IA.

Dan (Canadian AME)

[Jay Honeck]

> I leaned the mixture for the static runup and consequently got good
> results. I did NOT lean before takeoff. Perhaps that is significant.

That can be very significant on a hot day.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Russell Kent]

Ah so. Apologies Chuck.

Russell Kent

Dan Thomas wrote:

> Russell Kent > wrote in message >...
> > Chuck wrote:
> >
> > > Thanks again for your help. I'm going to ask my AME to check the fuel injection
> > > system.
> >
> > You can do what you want, but I suspect that your mechanic (A&P: Airframe and
> > Powerplant) would know more about the fuel injection system than your physician
> > (AME: Aviation Medical Examiner). :-)
> >
> > Russell Kent
>
> He'll be a Canadian. An AME here is an Aircraft Maintenance
> Engineer, roughly equivalent to an A&P-IA.
>
> Dan (Canadian AME)

[Jay Smith]

Nathan Young wrote:
> Are you sure they put the correct prop on the plane? I know some of
> the new 172 series were produced with 160hp and others with 180hp.
> Although you have to hope the mechanics did a better job - if you have
> a 160hp it is possible they swapped props with a 180hp 172.
> A cruise prop would drag down both the static RPM and climb
> performance. On the other hand, you should notice a few mph
> improvement in cruise (unless the prop is grossly wrong).

You will definitely feel the difference when you bring the power up for
takeoff.
The club I am in has three C172N's. One has a cruise prop. The first
time I flew it, I thought something was wrong when it took what seemed
(and actually was) a longer takeoff roll. I looked at the tach to see if
the RPM was low, but it was fine. Once leveled off in cruise, I noticed
the higher cruise airspeed and realized the prop difference.