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Engine Hesitation
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rveighta(at)comcast.net
Guest

Posted: Mon Sep 14, 2009 4:58 am Post subject: Engine Hesitation

I have a Lycoming IO-360 in my RV8A which  exhibits an engine hesitancy or "stumble" that is proving very difficult to diagnose. 

This problem shows up when taxiing back in after a flight, and in an RPM range of 750-1300. In flight there is no evidence of a stumble, 

and no stumble at initial start up, taxiing out for take off or during run-up. In other words, the engine only exhibits this behavior when it 

is warm.  

  

I have talked to some very knowledgable folks and have tried several things: (1) Reset the idle mixture, (2) removed and cleaned the 

servo finger screen, (3) removed the nozzles and placed them in a cup of acetone, which was then placed in a sonic cleaner for about 

an hour. After the nozzles were reinstalled, I test flew the plane and the stumble was gone. However, a subsequent test flight revealed 

that although the engine was running much smoother, an occasional stumble was still there.  

  

Additional facts: 

  

Oil temps are normal (around 180 deg F) 

Compression test is normal (all cylinders mid 70's) 

I'm using a Catto 3 blade prop 

  

Any and all suggestions you may have will be greatly appreciated. 

  

Thanks, 

  

Walt Shipley



 [quote][b]

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Mon Sep 14, 2009 5:59 am Post subject: Engine Hesitation

This type of troubleshooting forces you back to basics. Air, spark, fuel 

in right proportions at right time. When the engine is hot, vapor 

bubbles in fuel lines are possible. Tight valve stem to guide 

clearance(minor valve sticking) is possible. Coil faults can show up 

with heat.

Stumbles are usually a mixture problem, but you don't say if it happens 

with or without throttle movement. You don't say what time is on the 

engine. My guess is either some fuel boiling in the injector lines or a 

valve sticking, preventing sufficient mixture getting into the cylinder. 

Have you done a SB188 valve wobble check? Spark problems are less likely 

to be at low power and intermittent.



rveighta(at)comcast.net wrote:

 	  Quote: 	
		   I have a Lycoming IO-360 in my RV8A which  exhibits an engine hesitancy 

 or "stumble" that is proving very difficult to diagnose.

 

 This problem shows up when taxiing back in after a flight, and in an RPM 

 range of 750-1300. In flight there is no evidence of a stumble,

 

 and no stumble at initial start up, taxiing out for take off or during 

 run-up. In other words, the engine only exhibits this behavior when it

 

 is warm.

 

  

 

 I have talked to some very knowledgable folks and have tried several 

 things: (1) Reset the idle mixture, (2) removed and cleaned the

 

 servo finger screen, (3) removed the nozzles and placed them in a cup of 

 acetone, which was then placed in a sonic cleaner for about

 

 an hour. After the nozzles were reinstalled, I test flew the plane and 

 the stumble was gone. However, a subsequent test flight revealed

 

 that although the engine was running much smoother, an occasional 

 stumble was still there.

 

  

 

 Additional facts:

 

  

 

 Oil temps are normal (around 180 deg F)

 

 Compression test is normal (all cylinders mid 70's)

 

 I'm using a Catto 3 blade prop

 

  

 

 Any and all suggestions you may have will be greatly appreciated.

 

  

 

 Thanks,

 

  

 

 Walt Shipley

 

 *

 

 

 *

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

recapen(at)earthlink.net
Guest

Posted: Mon Sep 14, 2009 6:16 am Post subject: Engine Hesitation

Sounds like you may have a minor case of Vapor-Lock.  Like others, increasing the fuel flow makes it go away.  Have you tried running your boost pump to see if that helps?  There's been some discussion about this in the archives.



--

mrobert569(at)hotmail.com
Guest

Posted: Mon Sep 14, 2009 6:21 am Post subject: Engine Hesitation

Walt C

  

 have you tried checking for an intake leak.  It can cause exactly what you are talking about.

  

 Mike Robertson

 

  Date: Mon C 14 Sep 2009 12:56:45 +0000

From: rveighta(at)comcast.net

To: rv-list(at)matronics.com

Subject: Engine Hesitation



  .ExternalClass p {;}    I have a Lycoming IO-360 in my RV8A which  exhibits an engine hesitancy or "stumble" that is proving very difficult to diagnose.

 This problem shows up when taxiing back in after a flight C and in an RPM range of 750-1300. In flight there is no evidence of a stumble C

 and no stumble at initial start up C taxiing out for take off or during run-up. In other words C the engine only exhibits this behavior when it

 is warm. 

  

 I have talked to some very knowledgable folks and have tried several things: (1) Reset the idle mixture C (2) removed and cleaned the

 servo finger screen C (3) removed the nozzles and placed them in a cup of acetone C which was then placed in a sonic cleaner for about

 an hour. After the nozzles were reinstalled C I test flew the plane and the stumble was gone. However C a subsequent test flight revealed

 that although the engine was running much smoother C an occasional stumble was still there. 

  

 Additional facts:

  

 Oil temps are normal (around 180 deg F)

 Compression test is normal (all cylinders mid 70's)

 I'm using a Catto 3 blade prop

  

 Any and all suggestions you may have will be greatly appreciated.

  

 Thanks C

  

 Walt Shipley

 	  Quote: 	
		  



3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D



	
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rickpegser(at)yahoo.com
Guest

Posted: Mon Sep 14, 2009 8:44 am Post subject: Engine Hesitation

walt 

kelly is right. a little more info is needed . you need to do 97-3 from start to finish to check the fuel system. pressures are critical. what are your chts. 

rick

--- On Mon, 9/14/09, Kelly McMullen <kellym(at)aviating.com> wrote:

 	  Quote: 	
		   From: Kelly McMullen <kellym(at)aviating.com>

 Subject: Re: Engine Hesitation

 To: rv-list(at)matronics.com

 Date: Monday, September 14, 2009, 6:57 AM

 Kelly McMullen <kellym(at)aviating.com>

 This type of troubleshooting forces you back to basics.

 Air, spark, fuel in right proportions at right time. When

 the engine is hot, vapor bubbles in fuel lines are possible.

 Tight valve stem to guide clearance(minor valve sticking) is

 possible. Coil faults can show up with heat.

 Stumbles are usually a mixture problem, but you don't say

 if it happens with or without throttle movement. You don't

 say what time is on the engine. My guess is either some fuel

 boiling in the injector lines or a valve sticking,

 preventing sufficient mixture getting into the cylinder.

 Have you done a SB188 valve wobble check? Spark problems are

 less likely to be at low power and intermittent.

 rveighta(at)comcast.net

 wrote:

 > I have a Lycoming IO-360 in my RV8A which 

 exhibits an engine hesitancy or "stumble" that is proving

 very difficult to diagnose.

 > 

 > This problem shows up when taxiing back in after a

 flight, and in an RPM range of 750-1300. In flight there is

 no evidence of a stumble,

 > 

 > and no stumble at initial start up, taxiing out for

 take off or during run-up. In other words, the engine only

 exhibits this behavior when it

 > 

 > is warm.

 > 

 >  

 > I have talked to some very knowledgable folks and have

 tried several things: (1) Reset the idle mixture, (2)

 removed and cleaned the

 > 

 > servo finger screen, (3) removed the nozzles and

 placed them in a cup of acetone, which was then placed in a

 sonic cleaner for about

 > 

 > an hour. After the nozzles were reinstalled, I test

 flew the plane and the stumble was gone. However, a

 subsequent test flight revealed

 > 

 > that although the engine was running much smoother, an

 occasional stumble was still there.

 > 

 >  

 > Additional facts:

 > 

 >  

 > Oil temps are normal (around 180 deg F)

 > 

 > Compression test is normal (all cylinders mid 70's)

 > 

 > I'm using a Catto 3 blade prop

 > 

 >  

 > Any and all suggestions you may have will be greatly

 appreciated.

 > 

 >  

 > Thanks,

 > 

 >  

 > Walt Shipley

 > 

 > *

 > 

 > 

 > *

 Forum -

 FAQ,

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

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 Dralle, List Admin.

rveighta(at)comcast.net
Guest

Posted: Mon Sep 14, 2009 12:15 pm Post subject: Engine Hesitation

Mike, I'm not sure what you mean by checking for an intake leak. How do you go about doing that? 

  

Walt 



---

rveighta(at)comcast.net
Guest

Posted: Mon Sep 14, 2009 12:44 pm Post subject: Engine Hesitation

Kelly, you're so right. This kind of problem does force you back to the basics. To give you 

a bit more info, the stumble doesn't occur when the throttle is pushed up; only at a steady 

setting.  

  

I have experimented with tie wrapping foam insulation around the injector lines from the 

flow divider to the cylinders, but a test flight afterward revealed the problem was still there, 

so it appears fuel vaporization is not the culprit.  

  

Cylinder head temps are between 250-300 deg F on my Grand Rapids monitor. 

  

Total time on the engine is 750 TTSN and 300 STOH,     which included new valves. 

I have not done a SB188 valve wobble test.  

  

Thanks,      Walt 



---

mrobert569(at)hotmail.com
Guest

Posted: Mon Sep 14, 2009 1:54 pm Post subject: Engine Hesitation

Walt C

  

 Try tightening all the clamps and bolts on the intake system from the oil sump to the cylinder head and do a visual check on the rubber connectors for condition.  If everything appears ok then C very carefully C spray soapy water on the intake system while the engine is running.  You won't see bubbles because it is sucking but the engine will stumble if it a big leak C or you will see EGT and cylinder head temp changes.

  

 Mike

 

  Date: Mon C 14 Sep 2009 20:05:03 +0000

From: rveighta(at)comcast.net

To: rv-list(at)matronics.com

Subject: Re: Engine Hesitation



  .ExternalClass p {;}    Mike C I'm not sure what you mean by checking for an intake leak. How do you go about doing that?

  

 Walt

 

---

n8zg(at)mchsi.com
Guest

Posted: Mon Sep 14, 2009 2:17 pm Post subject: Engine Hesitation

Safest way is to connect the blower side of your shop vac to the intake and spray soapy water around all the joints looking for bubbles.Â    

   

There are more adventurous methods, but they present serious risk to life and limbâ€¦  

   

neal  

       

From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of rveighta(at)comcast.net

 Sent: Monday, September 14, 2009 3:05 PM

 To: rv-list(at)matronics.com

 Subject: Re: Engine Hesitation  

  

  

     

Mike, I'm not sure what you mean by checking for an intake leak. How do you go about doing that?  

   

Walt  

  

        [quote][b]

welchvincent(at)hotmail.c
Guest

Posted: Mon Sep 14, 2009 2:44 pm Post subject: Engine Hesitation

Walt C

  

 I know that it is off the subject but how did you end up with oil temps in the 180's?  I also have an RV-8A with an IO-360-A1A and a Hartzell constant speed prop C I have one mag and one lightspeed ignition.  On a warm day I will see 205 - 210 in cruise.  The only time I see 180 is in the winter.  My oil cooler is located behind #4 on the baffle.  It has a 1" C-Channel stand off and is well sealed to the baffle.  I have cleaned up as much as I can C the baffle seal is good as evidenced by CHT's in the low to mid 300's.  I even cut about two inches off the bottom of the cowl to open up the exit a bit.  How did you get 180's?????

  

 Vince 

 

  Date: Mon C 14 Sep 2009 12:56:45 +0000

From: rveighta(at)comcast.net

To: rv-list(at)matronics.com

Subject: Engine Hesitation



  .ExternalClass p {;}    I have a Lycoming IO-360 in my RV8A which  exhibits an engine hesitancy or "stumble" that is proving very difficult to diagnose.

 This problem shows up when taxiing back in after a flight C and in an RPM range of 750-1300. In flight there is no evidence of a stumble C

 and no stumble at initial start up C taxiing out for take off or during run-up. In other words C the engine only exhibits this behavior when it

 is warm. 

  

 I have talked to some very knowledgable folks and have tried several things: (1) Reset the idle mixture C (2) removed and cleaned the

 servo finger screen C (3) removed the nozzles and placed them in a cup of acetone C which was then placed in a sonic cleaner for about

 an hour. After the nozzles were reinstalled C I test flew the plane and the stumble was gone. However C a subsequent test flight revealed

 that although the engine was running much smoother C an occasional stumble was still there. 

  

 Additional facts:

  

 Oil temps are normal (around 180 deg F)

 Compression test is normal (all cylinders mid 70's)

 I'm using a Catto 3 blade prop

  

 Any and all suggestions you may have will be greatly appreciated.

  

 Thanks C

  

 Walt Shipley

 	  Quote: 	
		  



3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D



	
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rick.mcbride(at)me.com
Guest

Posted: Mon Sep 14, 2009 3:40 pm Post subject: Engine Hesitation

Vince,



Just as another point of reference, I have an IO360-A3B6D in my -8 with dual Lightspeed.   It has a firewall mounted oil cooler (13 row if I recall).  The plenum into the cooler has a butterfly valve.  Without shutting the valve I rarely see temperatures about 200 degrees unless in a climb on a hot day.  It's not uncommon that I have to close the valve partially to get temps to 180 or above.  With the valve open on a warm day my temps are usually in the 170s.

Rick McBride



On Sep 14, 2009, at 6:28 PM, Vincent Welch wrote:

 	  Quote: 	
		  Walt,

 

I know that it is off the subject but how did you end up with oil temps in the 180's?  I also have an RV-8A with an IO-360-A1A and a Hartzell constant speed prop, I have one mag and one lightspeed ignition.  On a warm day I will see 205 - 210 in cruise.  The only time I see 180 is in the winter.  My oil cooler is located behind #4 on the baffle.  It has a 1" C-Channel stand off and is well sealed to the baffle.  I have cleaned up as much as I can, the baffle seal is good as evidenced by CHT's in the low to mid 300's.  I even cut about two inches off the bottom of the cowl to open up the exit a bit.  How did you get 180's?????

 

Vince 

 

Date: Mon, 14 Sep 2009 12:56:45 +0000

From: rveighta(at)comcast.net (rveighta(at)comcast.net)

To: rv-list(at)matronics.com (rv-list(at)matronics.com)

Subject: Engine Hesitation



I have a Lycoming IO-360 in my RV8A which  exhibits an engine hesitancy or "stumble" that is proving very difficult to diagnose.

This problem shows up when taxiing back in after a flight, and in an RPM range of 750-1300. In flight there is no evidence of a stumble,

and no stumble at initial start up, taxiing out for take off or during run-up. In other words, the engine only exhibits this behavior when it

is warm. 

 

I have talked to some very knowledgable folks and have tried several things: (1) Reset the idle mixture, (2) removed and cleaned the

servo finger screen, (3) removed the nozzles and placed them in a cup of acetone, which was then placed in a sonic cleaner for about

an hour. After the nozzles were reinstalled, I test flew the plane and the stumble was gone. However, a subsequent test flight revealed

that although the engine was running much smoother, an occasional stumble was still there. 

 

Additional facts:

 

Oil temps are normal (around 180 deg F)

Compression test is normal (all cylinders mid 70's)

I'm using a Catto 3 blade prop

 

Any and all suggestions you may have will be greatly appreciated.

 

Thanks,

 

Walt Shipley

 	  Quote: 	
		  



3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D



	


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rveighta(at)comcast.net
Guest

Posted: Mon Sep 14, 2009 4:00 pm Post subject: Engine Hesitation

Vince, I too had temps above 200 F on warm days. That was before I installed louvered vents in the lower cowl. Now I have the reverse problem; 

hard to get the oil temps up on cold days.  

  

Walt 



---

welchvincent(at)hotmail.c
Guest

Posted: Mon Sep 14, 2009 5:59 pm Post subject: Engine Hesitation

Are you using the cowl louvers also Rick?

  

 Vince

 

  From: rick.mcbride(at)me.com

To: rv-list(at)matronics.com

Subject: Re: RV-List: Engine Hesitation

Date: Mon C 14 Sep 2009 19:30:56 -0400



Vince C 



 Just as another point of reference C I have an IO360-A3B6D in my -8 with dual Lightspeed.   It has a firewall mounted oil cooler (13 row if I recall).  The plenum into the cooler has a butterfly valve.  Without shutting the valve I rarely see temperatures about 200 degrees unless in a climb on a hot day.  It's not uncommon that I have to close the valve partially to get temps to 180 or above.  With the valve open on a warm day my temps are usually in the 170s.

 



 Rick McBride

 

  On Sep 14 C 2009 C at 6:28 PM C Vincent Welch wrote:

  	  Quote: 	
		   Walt C

 

I know that it is off the subject but how did you end up with oil temps in the 180's?  I also have an RV-8A with an IO-360-A1A and a Hartzell constant speed prop C I have one mag and one lightspeed ignition.  On a warm day I will see 205 - 210 in cruise.  The only time I see 180 is in the winter.  My oil cooler is located behind #4 on the baffle.  It has a 1" C-Channel stand off and is well sealed to the baffle.  I have cleaned up as much as I can C the baffle seal is good as evidenced by CHT's in the low to mid 300's.  I even cut about two inches off the bottom of the cowl to open up the exit a bit.  How did you get 180's?????

 

Vince 

 

  Date: Mon C 14 Sep 2009 12:56:45 +0000

From: rveighta(at)comcast.net (rveighta(at)comcast.net)

To: rv-list(at)matronics.com (rv-list(at)matronics.com)

Subject: Engine Hesitation



 I have a Lycoming IO-360 in my RV8A which  exhibits an engine hesitancy or "stumble" that is proving very difficult to diagnose.

This problem shows up when taxiing back in after a flight C and in an RPM range of 750-1300. In flight there is no evidence of a stumble C

and no stumble at initial start up C taxiing out for take off or during run-up. In other words C the engine only exhibits this behavior when it

is warm. 

 

I have talked to some very knowledgable folks and have tried several things: (1) Reset the idle mixture C (2) removed and cleaned the

servo finger screen C (3) removed the nozzles and placed them in a cup of acetone C which was then placed in a sonic cleaner for about

an hour. After the nozzles were reinstalled C I test flew the plane and the stumble was gone. However C a subsequent test flight revealed

that although the engine was running much smoother C an occasional stumble was still there. 

 

Additional facts:

 

Oil temps are normal (around 180 deg F)

Compression test is normal (all cylinders mid 70's)

I'm using a Catto 3 blade prop

 

Any and all suggestions you may have will be greatly appreciated.

 

Thanks C

 

Walt Shipley

 	  Quote: 	
		  



3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D



	


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welchvincent(at)hotmail.c
Guest

Posted: Mon Sep 14, 2009 5:59 pm Post subject: Engine Hesitation

I was looking at the louvers also.  I was holding that option as a last resort but it looks like I may have to go that way by next summer.  Thanks for the info.

  

 Vince

 

  Date: Mon C 14 Sep 2009 23:54:17 +0000

From: rveighta(at)comcast.net

To: rv-list(at)matronics.com

Subject: Re: Engine Hesitation



  .ExternalClass p {;}    Vince C I too had temps above 200 F on warm days. That was before I installed louvered vents in the lower cowl. Now I have the reverse problem;

 hard to get the oil temps up on cold days. 

  

 Walt

 

---

Bruce(at)glasair.org
Guest

Posted: Mon Sep 14, 2009 6:22 pm Post subject: Engine Hesitation

He  means to check the intake riser seals where they exit the sump. The easiest way  I know, is to spray each riser seal area with engine starter fluid while the  engine is running at low idle. If the engine speeds up, you have a  leak.

  

  

 

Bruce

www.Glasair.org  [quote]   

   --

garrys(at)tampabay.rr.com
Guest

Posted: Mon Sep 14, 2009 7:13 pm Post subject: Engine Hesitation

Where can I get info on these "cowl louvers"?

 Garry Stout

 [quote]   ---

rickpegser(at)yahoo.com
Guest

Posted: Tue Sep 15, 2009 12:14 am Post subject: Engine Hesitation

Walt



you have already tried the shotgun approach to solve this problem. Without a logging engine monitor, i have to go back to the basics. As said before, it is air, fuel or fire. 



you have yet to tell us how old this engine is.



you have played with the fuel side, this is not something you should do without the right tools. if you over lean these engines at max power you will be buying another one.



On the fire side i need to know what you have installed.

One the air side there could be any number of things that could be causing this. 



The problem with any experimental airplane, is that it is an experimental airplane. They are all one offs. There is no decent customer support, since almost everyone builds them a little different. 



rick

a+p/ia 25+ yrs.

--- On Mon, 9/14/09, Mike Robertson <mrobert569(at)hotmail.com> wrote:



[quote] From: Mike Robertson <mrobert569(at)hotmail.com>

 Subject: RE: Engine Hesitation

 To: "rv list" <rv-list(at)matronics.com>

 Date: Monday, September 14, 2009, 2:50 PM

 

 

 

 #yiv892795043 .hmmessage P

 {

 margin:0px;padding:0px;}

 #yiv892795043 {

 font-size:10pt;font-family:Verdana;}

 

 

  

 Walt,

 

  

 

 Try tightening all the clamps and bolts on the intake

 system from the oil sump to the cylinder head and do a

 visual check on the rubber connectors for condition. 

 If everything appears ok then, very carefully, spray soapy

 water on the intake system while the engine is

 running.  You won't see bubbles because it is

 sucking but the engine will stumble if it a big leak, or you

 will see EGT and cylinder head temp changes.

 

  

 

 Mike

  

 

 

 Date: Mon, 14 Sep 2009 20:05:03 +0000

 From: rveighta(at)comcast.net

 To: rv-list(at)matronics.com

 Subject: Re: Engine Hesitation

 

 

 

 #yiv892795043 .ExternalClass p

 {}

 

 

 

 Mike, I'm not sure what you mean by checking for an

 intake leak. How do you go about doing that?

 

  

 

 Walt

 

 

 ---

rick.mcbride(at)me.com
Guest

Posted: Tue Sep 15, 2009 3:55 am Post subject: Engine Hesitation

No I'm not.  I suspect my temps are due to a larger cooler, which is probably not a viable option for you.  The louvers sound like a good solution.



Rick

On Sep 14, 2009, at 9:58 PM, Vincent Welch wrote:

 	  Quote: 	
		  Are you using the cowl louvers also Rick?

 

Vince

 

From: rick.mcbride(at)me.com (rick.mcbride(at)me.com)

To: rv-list(at)matronics.com (rv-list(at)matronics.com)

Subject: Re: Engine Hesitation

Date: Mon, 14 Sep 2009 19:30:56 -0400



Vince,



Just as another point of reference, I have an IO360-A3B6D in my -8 with dual Lightspeed.   It has a firewall mounted oil cooler (13 row if I recall).  The plenum into the cooler has a butterfly valve.  Without shutting the valve I rarely see temperatures about 200 degrees unless in a climb on a hot day.  It's not uncommon that I have to close the valve partially to get temps to 180 or above.  With the valve open on a warm day my temps are usually in the 170s.

Rick McBride



On Sep 14, 2009, at 6:28 PM, Vincent Welch wrote:

 	  Quote: 	
		  Walt,

 

I know that it is off the subject but how did you end up with oil temps in the 180's?  I also have an RV-8A with an IO-360-A1A and a Hartzell constant speed prop, I have one mag and one lightspeed ignition.  On a warm day I will see 205 - 210 in cruise.  The only time I see 180 is in the winter.  My oil cooler is located behind #4 on the baffle.  It has a 1" C-Channel stand off and is well sealed to the baffle.  I have cleaned up as much as I can, the baffle seal is good as evidenced by CHT's in the low to mid 300's.  I even cut about two inches off the bottom of the cowl to open up the exit a bit.  How did you get 180's?????

 

Vince 

 

Date: Mon, 14 Sep 2009 12:56:45 +0000

From: rveighta(at)comcast.net (rveighta(at)comcast.net)

To: rv-list(at)matronics.com (rv-list(at)matronics.com)

Subject: Engine Hesitation



I have a Lycoming IO-360 in my RV8A which  exhibits an engine hesitancy or "stumble" that is proving very difficult to diagnose.

This problem shows up when taxiing back in after a flight, and in an RPM range of 750-1300. In flight there is no evidence of a stumble,

and no stumble at initial start up, taxiing out for take off or during run-up. In other words, the engine only exhibits this behavior when it

is warm. 

 

I have talked to some very knowledgable folks and have tried several things: (1) Reset the idle mixture, (2) removed and cleaned the

servo finger screen, (3) removed the nozzles and placed them in a cup of acetone, which was then placed in a sonic cleaner for about

an hour. After the nozzles were reinstalled, I test flew the plane and the stumble was gone. However, a subsequent test flight revealed

that although the engine was running much smoother, an occasional stumble was still there. 

 

Additional facts:

 

Oil temps are normal (around 180 deg F)

Compression test is normal (all cylinders mid 70's)

I'm using a Catto 3 blade prop

 

Any and all suggestions you may have will be greatly appreciated.

 

Thanks,

 

Walt Shipley

 	  Quote: 	
		  



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3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D



	


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rveighta(at)comcast.net
Guest

Posted: Tue Sep 15, 2009 5:06 am Post subject: Engine Hesitation

Rick, thanks for sticking with me on this problem. To answer your questions, the engine is a 1978 IO-360 B4A. It is equipped with two 

Bendix Magnitos  (R) S4LN-30, P/N 10-51360-29   (L) S4LN-21  P/N 10-51360-37.  I am using Unison  Aviation plugs, UREM37BY. 

Sparkplug wires are standard Lycoming.  

  

Thanks again..... 

  

Walt 

  



---

khorton

Joined: 18 Jun 2006
Posts: 4
Location: Ottawa, Canada

Posted: Tue Sep 15, 2009 4:18 pm Post subject: Re: Engine Hesitation

 	  rveighta(at)comcast.net wrote: 	
		  I have a Lycoming IO-360 in my RV8A which  exhibits an engine hesitancy or "stumble" that is proving very difficult to diagnose. 

This problem shows up when taxiing back in after a flight, and in an RPM range of 750-1300. In flight there is no evidence of a stumble, 

and no stumble at initial start up, taxiing out for take off or during run-up. In other words, the engine only exhibits this behavior when it 

is warm.  

	


Fuel injected Lycomings quite commonly run rough at idle if the engine is hot, as the fuel vaporizes in the fuel injection lines from the "spider" to the fuel injectors (it may be vaporizing in the spider too, so simply insulating the injection lines might not be an adequate test).  They run OK at higher power, as the pressure in the spider and those lines increases as the fuel flow increases.  At higher power the fuel pressure is high enough to keep the fuel from vaporizing. 



If this is the cause of your rough running, you might be able to improve things by switching to fuel injection nozzles from Air Flow Performance.  They sell nozzles with many different diameters.  Smaller nozzles require higher line pressure to get the same fuel flow, so this reduces the chances of fuel vaporizing at idle.    If you go down this road, you need to be sure you are still getting enough fuel flow at take-off power.  I don't know if you can just install these smaller nozzles and go flying, or if the fuel injection servo needs to be set up on a flow bench.  Don at AFP would know.

_________________
Kevin Horton RV-8
Ottawa, Canada
http://www.kilohotel.com/rv8

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