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Bonanza with IO-520BB idles rough

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martymitchell

Joined: 14 Sep 2008
Posts: 10
Location: Newport Beach, CA

Posted: Sun Sep 14, 2008 9:16 am Post subject: Bonanza with IO-520BB idles rough

I have an IO-520BB in my Beech Bonanza that runs rough at idle and low RPM.  I have changed the spark plugs, cleaned the injectors, checked the mag timing (just installed after 500 hour inspection and new distributor block), and had a mechanic check the idle fuel pump pressure and idle mixture setting.  



I also did a compression check and all cylinders are above 60/80. There doesn't seem to be any difference in drop with each mag at various RPM's.  I have not changed the ignition wires.



Any ideas on other things to look for?



Thanks!

_________________
Marty Mitchell
Bonanza N44GN

idewhirst(at)indtechnolog
Guest

Posted: Mon Sep 15, 2008 3:13 am Post subject: Bonanza with IO-520BB idles rough

I would look for an intake leak.



--

martymitchell

Joined: 14 Sep 2008
Posts: 10
Location: Newport Beach, CA

Posted: Mon Sep 15, 2008 7:06 am Post subject: Re: Bonanza with IO-520BB idles rough

I have verified that all the hose clamps are tight and that all the intake bolts are secure, but not sure where else to look and how to determine if it's leaking.



Thanks.

_________________
Marty Mitchell
Bonanza N44GN

Heavy707(at)comcast.net
Guest

Posted: Mon Sep 15, 2008 7:44 am Post subject: Bonanza with IO-520BB idles rough

What is the largest difference between cylinder  compression? You say all are at least 60/80 but how far apart are they and are  they very different from the last time they were taken? When is the last time  the prop governor was checked?

 Did it start being rough just after coming out of  the shop for repairs? Could it be cam related? Bad lobe on cam?

 Best of luck.

   [quote][b]

martymitchell

Joined: 14 Sep 2008
Posts: 10
Location: Newport Beach, CA

Posted: Mon Sep 15, 2008 8:02 am Post subject: Re: Bonanza with IO-520BB idles rough

Both mags were inspected, a new distributor block was installed on one due to a corroded terminal, and returned to the plane.  I only did a brief compression check to see if anything really bad happened to a cylinder, but will have to go back and do it more carefully to get the exact numbers and will compare with existing numbers.



Seems like the trouble began after the mags were pulled out and returned.  



I suppose it could be a bad cam lobe.  The engine is 1500 hours TSO.



The prop governor has not been checked for 1500 hours as far as I know.



I'm planning to check the ignition wires today.

_________________
Marty Mitchell
Bonanza N44GN

martymitchell

Joined: 14 Sep 2008
Posts: 10
Location: Newport Beach, CA

Posted: Mon Sep 15, 2008 9:51 pm Post subject: Re: Bonanza with IO-520BB idles rough

Problem Found! I did a second compression check and took my time. Although all of the compressions are in the low to mid 60's, it appears that each cylinder has a valve leak, one exhaust and 5 intakes. I suppse that is why it idles so rough. 



Thank you all for your help and suggestions. I should have started off with a careful compression check.

_________________
Marty Mitchell
Bonanza N44GN

BobsV35B(at)aol.com
Guest

Posted: Tue Sep 16, 2008 5:36 am Post subject: Bonanza with IO-520BB idles rough

Good Morning Marty,

  

 I am getting in on this thread very late, but didn't I see that your  roughness came on suddenly following a repair to an ignition component?

  

 I would not feel that your cylinder compressions would have caused a sudden  change in operation.

  

 Have you looked at the cylinders with a borescope?

  

 Continental now tells us that the older compression check done alone is not  valid. You really need to take a good look at the valve face.  That will  tell you if the valve is leaking under operating conditions. Many valves that  show leakage via a static compression check will seal just fine under normal  operations. I would look further for your problem.  

  

 I think there may be a newer version of the Continental Motors Service  Bulletin concerning cylinder testing, but the one I have before me right now is  dated 2003. It is SB03-3. Be sure you have that one or a newer version before  you start tearing things apart!

  

 Happy Skies,

  

 Old Bob

  

  In a message dated 9/16/2008 12:52:44 A.M. Central Daylight Time,  orders(at)martymitchell.com writes:

  	  Quote: 	
		  -->    Beech-List message posted by: "martymitchell"    <orders(at)martymitchell.com>



Problem Found! I did a second    compression check and took my time. Although all of the compressions are in    the low to mid 60's, it appears that each cylinder has a valve leak, one    exhaust and 5 intakes. I suppse that is why it idles so rough. 



Thank    you all for your help and suggestions. I should have started off with a    careful compression check.



--------

Marty Mitchell

Bonanza    N44GN

	




Psssst...Have you heard the news? There's a new fashion blog, plus the latest fall trends and hair styles at StyleList.com.

  [quote][b]

martymitchell

Joined: 14 Sep 2008
Posts: 10
Location: Newport Beach, CA

Posted: Tue Sep 16, 2008 7:03 am Post subject: Re: Bonanza with IO-520BB idles rough

Thanks Old Bob.  Good advice.  I am aware of Service Bulletin SB03-3 and have read it.  Turns out that I mistakenly reported my problem as being 5 intake leaks, when in fact, air was leaking thru the crankcase breather, so they are actually ring leaks.



So I have 1 exhaust valve leak and 5 that are leaking past the rings.



I'm not sure that explains idle roughness.  I'm just about ready to pull the mags and have them re-checked for proper internal timing but the mag shop says it not my problem.  



Still very confused....

_________________
Marty Mitchell
Bonanza N44GN

thender(at)adelphia.net
Guest

Posted: Tue Sep 16, 2008 8:07 pm Post subject: Bonanza with IO-520BB idles rough

This sounds dumb..   but have you verified that all the plug wires are going 

to the right places, and that they aren't damaged, etc?



-TH

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martymitchell

Joined: 14 Sep 2008
Posts: 10
Location: Newport Beach, CA

Posted: Tue Sep 16, 2008 8:14 pm Post subject: Re: Bonanza with IO-520BB idles rough

I did test all the ignition wire with one of those ignition wire testers.  I believe it only checks for shorts to ground but does not check for opens.  I'm sure all the wires are in the right place or it would run REAL bad.



There are a couple damaged spots but just to the outer vinyl, no further.



Any other ideas?



Marty

_________________
Marty Mitchell
Bonanza N44GN

hal_kempthorne(at)sbcglob
Guest

Posted: Wed Sep 17, 2008 9:33 am Post subject: Bonanza with IO-520BB idles rough

An intake air leak will be a factor at low speeds and less so at higher speeds.   

  

hal 

(Finally rid of the Debonair - but I loved her for all her faults) 

Now flying an RV6-a (Lycoming) 



 

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pankajnagarkoti86

Joined: 12 Oct 2009
Posts: 2

Posted: Mon Oct 12, 2009 2:10 pm Post subject: Re: Bonanza with IO-520BB idles rough

no,Any ideas| 

 ......because i do not knowledge for that.

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