Rough Engine Concern

[George]

11 hours ago, tony said:

Why did you overhaul the mag?  When the engine was running rough did you do an inflight mag check?  I would suspect the  mag that was rebuilt 50 hours ago.  A bad cap in the mag  would have similar symptoms.  

Mag sent off for overhaul during prebuy at DMs facility. They could not get the engine started and found that left mag cam points were worn. Did not do inflight mag check. Oil change and investigation today w mechanic if it happens again inflight will try mag check.

[George]

11 hours ago, bradp said:

George notes a non normal mixture sweep to peak.

Thinking about the "differential diagnosis" and the symptom- should consider spark and more likely injection / servo fuel delivery issues if you can rule out lingering water.

Do you have an engine monitor and can you upload the data?

Have you tried doing a LOP magneto check? What kind of mags do you have?

Are all cylinders peaking together or is one too lean (induction leak, fuel injector blockage) or too rich?

Just PP thoughts as Anthony says


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 I have Insight 602 GEM not sure if you can download info. I will have to check or perhaps the forum can answer. 

Have not tried LOP mag check on the Slick Mags. Will try today after oil change and some additional investigative work.

On 2 of the 3 legs the #4 cylinder was peaking well before the remaining cylinders.

"PP thoughts" ??

Thank you for the ideas.

GHW

[nels]

I think you said the plugs are all new about 15 hrs ago? Would it be worth trading the #4 plug set with another cylinder to see if the problem follows the plug set? Simple check to rule out a possible inferior new plug. 

You might also look at plug wires that might move with the frontal air blowing against them. Possible chaffed wire getting grounded. I imagine the plug wires got moved around when the plugs were changed and possibly a tie strap needs to be added.

[kmyfm20s]

Have you checked for and induction leak on #4?

[Bob_Belville]

19 hours ago, Marauder said:

Bob -- I think the big O rings on our bladder caps call for the fluorosilicone ones. I saw them at one time on the Aircraft Spruce site but can't find them now. They were expensive, something like $50 each. 

I will call the new owners of the bladder STC and ask what should be used. I know I also saw someone on Beechtalk selling them. I will look for that information as well.

 

19 hours ago, jetdriven said:

The Shaw aero bladder cap o-rings are not the same size as the Beech ones or the ones listed in the Mooney IPC. However someone on here did find the right ones at Spruce for a little less than the price from O&N, which was like 110$ for all 4. Yikes. 

Sky Geek shows the Military Specification M25988/1-338 O-Ring which is the right material, but I'm not sure of the size. But Sky Geek shows all kinds of stuff they do not stock. Their price is $7.88 ea but 25 must be ordered = $197. 

I wonder if someone like DMax or LASAR orders enough to be able to offer a better price.

My E only has 2 caps.

Edit, 12/26: Will this work? www.oringsusa.com   $20.90 ea.  http://www.oringsusa.com/catalog/product_info.php/cPath/21_90_94/products_id/94000338

Chris, I have tried to contact the company that now owns the O&N STC about the 10 gallon add on and they have not responded. (Their website requires confirmation that email inquiries are not machine generated. Hardly customer friendly.)  

[George]

So not water issue best I can tell. No water present when I checked the fuel this morning. Mag checks at 1700 rpm showed maybe a 50 rpm drop L&R. Flew the plane in the pattern and first lap at pattern altitude no issue. Second & third lap the occasional rough engine / knock... at 25 squared. Was getting  a 100 rpm drop during the occasional rough engine bouts when I check the L&R mags...it seemed to make the roughness worse / more noticeable. No maintenance today hopefully tomorrow I can pass along the forum thoughts..

 

GHW 

[Lrn2Fly]

Classic symptoms of an intake leak on #4 tube.  Sometimes it's there, sometimes it's gone.  Depending on manifold pressure, atmospheric pressure, and mechanical security, the EGT will act sporadically and frustrate the troubleshooting efforts.  But the core symptoms point at either too much air or too little fuel on one cylinder.  Since you're flying a C model, that rules out injectors.

The easiest test to do is a lean range test - at 2000' and 23/2300, pull the mixture. There should be at least a 200' rise on all 4 cylinders before they peak.  If one cylinder peaks well before the others, and does not have a healthy amount of rise, it's not getting enough fuel OR  too much air.

Have you put a socket on the intake tube bolts and check for security?

[George]

2 hours ago, Lrn2Fly said:

Classic symptoms of an intake leak on #4 tube.  Sometimes it's there, sometimes it's gone.  Depending on manifold pressure, atmospheric pressure, and mechanical security, the EGT will act sporadically and frustrate the troubleshooting efforts.  But the core symptoms point at either too much air or too little fuel on one cylinder.  Since you're flying a C model, that rules out injectors.

The easiest test to do is a lean range test - at 2000' and 23/2300, pull the mixture. There should be at least a 200' rise on all 4 cylinders before they peak.  If one cylinder peaks well before the others, and does not have a healthy amount of rise, it's not getting enough fuel OR  too much air.

Have you put a socket on the intake tube bolts and check for security?

Will give this a try tomorrow weather permitting. Will also check bolts as well. Am I correct to assume the order of cylinders starts with farthest forward as #1?  Which would make #4 closest to firewall?

 

Thanks

GHW

[Guest]

53 minutes ago, George said:

Will give this a try tomorrow weather permitting. Will also check bolts as well. Am I correct to assume the order of cylinders starts with farthest forward as #1?  Which would make #4 closest to firewall?

 

Thanks

GHW

On your Lycoming the front right is number 1, back right is number 3, front left is number 2 back left is number 4.  The numbers are cast into the crankcase beside the cylinders.

Clarence

[bradp]

On your Lycoming the front right is number 1, back right is number 3, front left is number 2 back right is number 4.  The numbers are cast into the crankcase beside the cylinders.
Clarence

Minor type. Back left is #4. This is from the perspective as if you're sitting in the cockpit.


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[Guest]

7 minutes ago, bradp said:

 

Minor type. Back left is #4. This is from the perspective as if you're sitting in the cockpit.


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Corrected it, good catch!

Clarence

[carusoam]

Fuzzy PP ideas...  things that may cause a skip

1) Since we are possibly talking about air leaks on the four intake tubes of an O360...

It would be helpful to know the last time the seals were replaced...are they silicone or cork? Gasket at one end rubber hose/sleeve at the other...(?)  (one of my more ancient memories)

2) how thick is the blue goo inside the tubes?  In my Old C's intake tubes there was quite a bit of thick coating inside the intake tubes

3) Are the spark plugs Champions.  Have they had their resistance checked?

4) Do the lower plugs have a growing collection of lead balls collecting in them?  Befor learning to lean aggressively on the ground, I learned how large the lead shot can get before creating a hazard to the lower plug's ignition.

5) Since it is only happening on one cylinder, it is probably not related to mag timing shifting after mag maintenance...

6) If they are Champion spark plugs in there, write a letter of displeasure to the manufacturer, then check the resistance of the plug...

Just one PP's ideas of what is possibly going on...  My C had neither FF, or an engine monitor.  All maintenance was done by following logic and chatting with the mechanics during it's annual...  

It is much better to have data that you can share.

Best regards,

-a-

[George]

1 hour ago, carusoam said:

Fuzzy PP ideas...  things that may cause a skip

1) Since we are possibly talking about air leaks on the four intake tubes of an O360...

It would be helpful to know the last time the seals were replaced...are they silicone or cork? Gasket at one end rubber hose/sleeve at the other...(?)  (one of my more ancient memories)

2) how thick is the blue goo inside the tubes?  In my Old C's intake tubes there was quite a bit of thick coating inside the intake tubes

3) Are the spark plugs Champions.  Have they had their resistance checked?

4) Do the lower plugs have a growing collection of lead balls collecting in them?  Befor learning to lean aggressively on the ground, I learned how large the lead shot can get before creating a hazard to the lower plug's ignition.

5) Since it is only happening on one cylinder, it is probably not related to mag timing shifting after mag maintenance...

6) If they are Champion spark plugs in there, write a letter of displeasure to the manufacturer, then check the resistance of the plug...

Just one PP's ideas of what is possibly going on...  My C had neither FF, or an engine monitor.  All maintenance was done by following logic and chatting with the mechanics during it's annual...  

It is much better to have data that you can share.

Best regards,

-a-

Engine was field overhaul 1996 and currently has almost 500 SMOH...I'm guessing they seals would have been replaced during overhaul. I will check the logs in morning.

Have not looked in the tubes will pass along to A&P.

Tempest plugs (Dec.12) all new 15 - 20 hrs since installation with no issues until now.  Will take a look at lower plugs tomorrow.

Thank you for your input..

GHW

[carusoam]

Having your mechanic pull an intake tube shouldn't be too time consuming...

If you want to save some time on the bill, taking the cowl off is typical PP work. Knowing which intake tube you want to pull would help.  A can of carb cleaner, towels, and a seal, would be good if you want to remove the the tube for cleaning...

This is a simple job.  I did it under the supervision of a mechanic during an annual...several years ago.

500 hours probably isn't a lot. But, I was surprised with how much had collected in the tubes and rocker covers.  I have no idea how many hours the goo collected for before I cleaned mine.  All four were equally full up with goo...

Great project to work with your mechanic on.  Helps to get to know that person.  He gets to know you.  All is good this way.

Best regards,

-a-

[George]

15 minutes ago, carusoam said:

Having your mechanic pull an intake tube shouldn't be too time consuming...

If you want to save some time on the bill, taking the cowl off is typical PP work. Knowing which intake tube you want to pull would help.  A can of carb cleaner, towels, and a seal, would be good if you want to remove the the tube for cleaning...

This is a simple job.  I did it under the supervision of a mechanic during an annual...several years ago.

500 hours probably isn't a lot. But, I was surprised with how much had collected in the tubes and rocker covers.  I have no idea how many hours the goo collected for before I cleaned mine.  All four were equally full up with goo...

Great project to work with your mechanic on.  Helps to get to know that person.  He gets to know you.  All is good this way.

Best regards,

-a-

Thanks...will let you know what we find..

GHW

[moodychief]

I have a 63 C model and had a similar situation that kept getting worse.  We OH'd mags, new plugs/wires, rebuilt carb, checked timing, etc. And still had the intermittent problem.  We then started troubleshooting the fuel lines.  We finally found the culprit when we pushed air through the fuel lines.  After the fuel line leaves the gascalator the line has a short 4-6 inch run inside the cockpit on the left front of the nosegear doghouse.  The line had abrasion tape where it went through a circular hole.  After removing the tape we discovered it had been rubbing enough on the upper part of the line that there was a crack allowing air in the line. You couldn't see anything with the black tape on it.  After replacing that section I have flown 800 hours without any issues.  This may not be your issue but it is very cheap to do a visual inspection before spending a lot of money like I did trying to track it down.

[George]

Thank you all for your input. May have found the problem. I pulled plugs today and three of the four bottom plugs had lead deposits. Lower number 4 cylinder plug had a large deposit of lead. After cleaning the plugs we took it up for about 15 minutes and did not notice any issues with roughness. I will keep my fingers crossed in hopes that the lead deposits were in fact the problem.

Did someone say something about leaning aggressively? LOL

However I do have another question...With the build up of lead on the plugs would we not notice an issue while doing mag check?

GHW

[cctsurf]

25 minutes ago, George said:

Did someone say something about leaning aggressively? LOL

According to Mike Busch, aggressive leaning means to lean according to Lycoming's new guidance on the subject: lean always other than takeoff and early climb or starting the engine.  For taxiing or run-up, lean to best power mixture (highest rpm).  I tried this for the first time recently and found that it was WAY leaner than I had been "aggressively" leaning to previously.  I have been listening to Mike's webinars quite a bit recently, they are excellent!  https://www.savvyaviation.com/savvyaviation-home/resources/mikes-webinars/

I can't remember which webinar specifically contains this guidance, probably the one on leaning or advanced leaning.

Lycoming's Leaning recommendations: http://sdcap.us/wp-content/uploads/2015/05/Lycoming-Engine-Leaning-Procedures.pdf

Edited December 31, 2016 by cctsurf
Add Lycoming link

[Cyril Gibb]

58 minutes ago, cctsurf said:

For taxiing or run-up, lean to best power mixture (highest rpm). 

Agree with everything else except taxiing.  I taxi as lean as possible while just barely keeping the engine from stumbling.  An additional safety advantage is when taking off.  My engine at full throttle would die at the lean setting I taxi with.  If you taxi at best power and get distracted, then there's a chance you could inadvertently take off without going full rich at a fuel flow that wouldn't feel rough but would be damaging to cylinders (or worse).

[carusoam]

One of these days, George...

you will be quoting these ideas to the next new guy on the block...

Soon, you will collect some first hand knowledge that the next guy may not have yet.

its amazing how much useable information you can get at MS.

Best regards,

-a-

[George]

8 minutes ago, carusoam said:

One of these days, George...

you will be quoting these ideas to the next new guy on the block...

Soon, you will collect some first hand knowledge that the next guy may not have yet.

its amazing how much useable information you can get at MS.

Best regards,

-a-

I look forward to when I can offer my experience and knowledge as time goes on...right now I am taking it all in to keep the plane healthy and my boys safely building time.

Going to fly a couple short legs tomorrow to see if the plugs were the problem.

[Hank]

27 minutes ago, Cyril Gibb said:

Agree with everything else except taxiing.  I taxi as lean as possible while just barely keeping the engine from stumbling.  An additional safety advantage is when taking off.  My engine at full throttle would die at the lean setting I taxi with.  If you taxi at best power and get distracted, then there's a chance you could inadvertently take off without going full rich at a fuel flow that wouldn't feel rough but would be damaging to cylinders (or worse).

That's hiwmi lean on the ground, too. I recently parked in the grass,and the engine nearly died when I advanced the throttle less than halfway to pull up onto the pavement. The last time I flew a 172, I leaned out in the runway after slowing, the engine quit and we rolled clear to restart; took rather a lot of priming to reestablish fuel flow . . . Since I've been doing this, I find almost no lead in my plugs at annual.

[George]

On ‎12‎/‎23‎/‎2016 at 8:35 PM, Dham said:

D you know what your fuel flow was? Had something similar and it was the fuel flow divider the diaphragm had a cut in it.


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Do not remember...will advise during annual..

Thanks

[George]

On ‎12‎/‎25‎/‎2016 at 8:07 PM, bradp said:

George notes a non normal mixture sweep to peak.

Thinking about the "differential diagnosis" and the symptom- should consider spark and more likely injection / servo fuel delivery issues if you can rule out lingering water.

Do you have an engine monitor and can you upload the data?

Have you tried doing a LOP magneto check? What kind of mags do you have?

Are all cylinders peaking together or is one too lean (induction leak, fuel injector blockage) or too rich?

Just PP thoughts as Anthony says


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I feel the engine is running on the lean side w/o leaning. Flew yesterday and the GEM was indicating the EGTs graphs already in the area of peak EGT and I had not even touched the mixture control.

A&P checked for induction leaks (visually and carb cleaner sprayed near induction potential leak areas) non found.

All cylinder EGTs rising pretty close together.

All plugs firing after checking with GEM. Each cylinder had about 50-75 rise in temp when operating on either L or R mag.

Slick mags

 Fuel injector would only be on IO360...correct?

Thanks for thoughts..

GHW

[George]

On ‎12‎/‎30‎/‎2016 at 11:02 AM, moodychief said:

I have a 63 C model and had a similar situation that kept getting worse.  We OH'd mags, new plugs/wires, rebuilt carb, checked timing, etc. And still had the intermittent problem.  We then started troubleshooting the fuel lines.  We finally found the culprit when we pushed air through the fuel lines.  After the fuel line leaves the gascalator the line has a short 4-6 inch run inside the cockpit on the left front of the nosegear doghouse.  The line had abrasion tape where it went through a circular hole.  After removing the tape we discovered it had been rubbing enough on the upper part of the line that there was a crack allowing air in the line. You couldn't see anything with the black tape on it.  After replacing that section I have flown 800 hours without any issues.  This may not be your issue but it is very cheap to do a visual inspection before spending a lot of money like I did trying to track it down.

I'm going to check that fuel line..still having issue..engine seems to be running lean before I touch mixture.

thanks

GHW