Cylinder #3 Went Cold on EGT

[drstephensugiono]

Flew back from Monterey, CA....to...Redlands, CA.  Very smooth flight for 1 hr 39 min.  8 miles from the airport I descended from 3K feet for left base RWY8.  I don't know why I open the cowl flaps,  usually do it on the ground, figure it was a 105 deg day.  Well, on final i gve little throttle and noticed it was missing and cyl #3 on the egt and cht went cold.  landed and lean it out trying to clean out foul plugs but to no avail!  

Mechanic change both plugs on that cylinder, fuel flows nicely and cleaned injector, compression were in mid 70's.  We are stumped!  

Anyone with similar situation?

[jackn]

Just a thought. If you descend at full prop fwd & low MP there is a posibility of the prop driving the cylinders. This will loosen the rings and let oil bypass the rings. This could be made worse with cold cylinders.

[cbarry]

It sounds like that channel on the monitor went offline.  Try temporarily switching a probe and it if #3 comes alive, it's not the monitor.

[Nathan Peterson]

You said it was missing... did you try checking the Mag check... Left watch for a rise, Right watch for a rise?

Since you replaced the plugs and they were good... try going up stream.

[jetdriven]

Pulling the cowl flaps open while going rich on the mixture could result in a temporary stuck valve due to very rapid cooling.  I am not a shock cooling believer, but pulling power, opening cowl flaps, and richening the mixture might cause a very rapid cooling event. Lycoming recommends no more than 50 degrees a minute. You may have exceeded that.

[drstephensugiono]

Found the problem.....Right Magneto is bad!  started it on both mags.....feel the miss.  Turn one click to to the left mag and NO change.  Turn 2 clicks to right mag and it missed and stumbled very badly!  I gues I might as well change both mags.  

[jetdriven]

Sounds more like a bad spark plug or lead on the top of #3.

[Nathan Peterson]

Make sure you look @ # 3 cylinder and check for a rise on the EGT on the right Mag. If all other cylinders are rising and # 3 isn't .  I would check for leads and that they are not grounding themselves out.  You still would have a good Right Mag as indicated by the other cylinders rising.  Check the P-lead... make sure the spark plug isn't grounding out somewhere.

I agree with Byron on the Lead, spring.

I would hate for you to go out and buy new Mags when that really isn't the problem.

 

Please check this out:    http://www.sacskyranch.com/eng37.htm

[Piloto]

I had the same experience and found out it was a loose nut on the fuel injector line. If it would have been a bad mag or plug the egt temp would have gone up as it happens when you turn a mag off during run up. In your case it was likely a clogged fuel injector. I would also check the gascolator and fuel servo fuel screens for contaminants or debris. The beauty of having an engine analyzer is that you can pinpoint the faulty cylinder thus saving a lot of time in troubleshooting a problem like this.

José 

[drstephensugiono]

Checked the mags like U guys suggested and turning it to the left was still missing....no rise.  checked the right, no rise but stumbling more.  Checked top plug of cyl #3 and no spark...checked wire and leads...was fine.  Took right mag off and found points heavy pitted...ran to Aircraft Spruce for parts..put it on...now we have spark at the plug.  Guess what....still missing!!!  The nubie mechanic that I fired said there were spark and he cleaned the injector....well, I will check the injector next week w Casper of Red Aero Aviation thats been doing this with me.  Hope its not a valve or head!  The fired, nubie mechanic said he checked compression too......I will have to check it myself again!  Signing out for now till something new.....I still love my TLS Bravo !

[carusoam]

While you are in there, check the resistance of the spark plugs. There has been some discussion here lately on the topic....

Best regards,

-a-

[drstephensugiono]

2 new plugs....old plugs only had approx 850 ohms each!

 

[MooneyMitch]

I'm sorry if I missed it somewhere along this thread but, did anyone suggest checking the integrity [cable tester] of the high tension [spark plug] wire or the actual connection quality at either end? Mag or plug end?

 

 

[drstephensugiono]

Eureka!!!! Broken valve springs! Closes valve for good compression until u start engine. Will post pics later!

Edited January 9, 2016 by drstephensugiono

[drstephensugiono]

wont allow me to post my pics

[Nathan Peterson]

Eureka!!!! Broken valve springs! Closes valve for good compression until u start engine. Will post pics later!

I'm glad that you were able to diagnose the problem... you had said " I hope it wasn't a valve or head problem"

would love to see pic if you can figure it out. Nate

[drstephensugiono]

Ok....I can't post my attachment pics but I could put them on my gallery....! My plane runs so much smoother with new points, condensers on both mags, and new valve springs on cylinder #3.

[carusoam]

That photo sure does explain a lot...

My next thought is, what caused that to happen in the first place?

Sticky valve or another symptom that may need to be serviced.

Best regards,

-a-

[drstephensugiono]

Carusoam......don't scare me......I will call my mechanic to see if the valves moved freely and the rockers had no play!

[carusoam]

Stephen,

Not trying to....

My only experience on valves was a stuck/bent one in a lyc O-360 that sat too long prior to my purchase.

My engineering senses would have me looking a little deeper, like you indicated, while your mechanic is in there.

There is some TLS/Bravo experience on this site that may be more fitting/helpful.

Best regards,

-a-

[thinwing]

Broken valve spring..uhoh.....better have a mechanic do a valve wobble test on that cylinder...also get him to boroscope the "burn pattern "on that cylinder...how was the spring replaced???Did they pull the jug or do the rope trick...good luck..kpc

[drstephensugiono]

Did the wobble test.....boroscope prior to finding out the springs broken....did not remove jug.