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Mixture too lean; misfires; 0.7 GAMI spread


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4 minutes ago, carusoam said:

In the latest Savvy graph...

EGT1 & CHT1 are not warming up like the others right from start-up...

What happens at 5:00 into the run?  A peak for some reason... but EGT1 is low but bumps up at this time...   EGT4 screams higher,  while other two aren’t moving... what knobs got moved here?

In the flight EGT4 is getting hotter than the others....

EGT1 is staying colder and really falling out the bottom at the end of the flight like it started....

See if you can point out where the mag tests were... time and switch position... because it isn’t super obvious with all the different things going on...

when the prop knob gets pulled...

+1 on the baby jar test...

Something is weird at 5minutes and 15minutes where the EGT4 has unexplained peaks like a plug not behaving...

I’ll be back tomorrow...

-a-

 

 

Yeah, not sure what's going on with EGT1/CHT1.

At the 5:00 minute mark I was at idle and had been slowly leaning from full rich to almost ICO. As soon as it seemed like the engine was going to cut out, I restored the mixture. That's the exact moment when it started to stumble from being too lean.

EGT4 is 20-50° hotter than the other cylinders in flight, aye, but I'm told that's normal and likely due to minute variations in probe placement. I'll know more when I open her up again.

"EGT1 is staying colder and really falling out the bottom at the end of the flight like it started...." You mean at about 42:05? That's at idle, taxi'ing back to the hangar after landing. (Mile long runway, several minutes taxi time.)

"See if you can point out where the mag tests were... time and switch position... because it isn’t super obvious with all the different things going on..." I kinda did, with timestamps and video, but here goes.

On the ground mag check (video):

  • 10:40-11:05 left mag
  • 11:05-11:20 both
  • 11:25-11:50 right mag
  • 11:55-12:10 both
  • 12:15-12:30 left mag (again)
  • 12:35 back to both

(Turns out I did have about 15 seconds per position, I remember waiting for everything to stabilize before moving to the next step in the check, but didn't realize it had been ~15 seconds between key turns.)

In flight mag check, at approx. 65% power (video):

  • 34:15-34:35 left mag
  • 34:35-34:50 both
  • 34:50-35:10 right mag
  • 35:15 back to both

"Something is weird at 5minutes and 15minutes where the EGT4 has unexplained peaks like a plug not behaving..." I'm not seeing anything at 5:15. At 4:40 there's a spike, but that's the idle mixture test. At 5:15 EGT4 is 16°F hotter than EGT3, and the total spread is 136°F. I've had bad plugs before (hence having them replaced in December), I know what it looks like when one cylinder isn't firing during a mag check. I don't see that here. (And wouldn't a plug not behaving cause the EGT to drop significantly, rather than peak? No combustion = no exhaust gases.)

Yeah, here's a run-up I did for my A&P mid-December (that resulted in the plugs being swapped out for new); note how EGT2 drops on the right mag, eventually dropping off the scope completely: https://drive.google.com/open?id=1GmvuzgYgduywOs6nfY755J92O78igqP4

 

 

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4 hours ago, chrixxer said:

Baby jar test?

Injectors were inspected and cleaned 6 months / 100 hours ago. Can revisit, once my A&P has time to come up for air. Mixture is going to the stops on the servo.

It’s the flow check referenced here.  Basically you put small jars on the jugs and put each injector into the jar while hooked to the spider.  The flow should be even and no spitting.  You may have a misbehaving injector that will cause symptoms in other cylinders as well.  Cleaning may be needed again.  They are easily compromised by tiny debris.  Even the cleaning process can compromise them with a piece of rag.  The cleaning SB is also referenced.  Do you ever get particulates when you sump the fuel?

 

https://www.lycoming.com/content/improved-fuel-injector-nozzles

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1 minute ago, takair said:

It’s the flow check referenced here.  Basically you put small jars on the jugs and put each injector into the jar while hooked to the spider.  The flow should be even and no spitting.  You may have a misbehaving injector that will cause symptoms in other cylinders as well.  Cleaning may be needed again.  They are easily compromised by tiny debris.  Even the cleaning process can compromise them with a piece of rag.  The cleaning SB is also referenced.  Do you ever get particulates when you sump the fuel?

 

https://www.lycoming.com/content/improved-fuel-injector-nozzles

Cool, thanks!

Particulates? Never that I've seen. Tanks were stripped and resealed about 3 years ago.

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1 minute ago, chrixxer said:

Cool, thanks!

Particulates? Never that I've seen. Tanks were stripped and resealed about 3 years ago.

Particulates are just costly crud....:-). Hard to say what can make it to the injectors.  Even an eyelash is enough....

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Just now, takair said:

Particulates are just costly crud....:-). Hard to say what can make it to the injectors.  Even an eyelash is enough....

Though this bit from the Lycoming document you linked, suggests partial blockage would manifest itself visibly on the engine data:

When fuel flow is only partially blocked by dirt in the injector nozzle, the exhaust gas temperature will rise and not respond to mixture control until idle cut-off is reached. The reason for this is that the blockage now becomes the primary restriction and is independent of mixture-control position.

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2 hours ago, chrixxer said:

Though this bit from the Lycoming document you linked, suggests partial blockage would manifest itself visibly on the engine data:

When fuel flow is only partially blocked by dirt in the injector nozzle, the exhaust gas temperature will rise and not respond to mixture control until idle cut-off is reached. The reason for this is that the blockage now becomes the primary restriction and is independent of mixture-control position.

Maybe blockage is the wrong term.  A piece of fiber can cause a change in the spray pattern, which changes the mixture.  It can vary with fuel pressure and power settings.  To determine if you had a crud, have the mechanic do the initial cleaning over a clean white cloth to catch any debris.  By the way, my worst experience with this was shortly after having bladders installed.  Any servicing of the fuel system is an opportunity for something to move through the system and get into the injectors.  For example, if a fiber remained in the servo after overhaul, it could easily make it to the injectors.  IDK...I could be wrong, but the injectors are rather easy to check....and can be frustrating analyze. 

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I think you have an intake leak on number 1.  How does the plane idle?  Nice and smooth, or a little rough?  

Your number 1 EGT is is 100° cooler at idle.  As you advance the throttle, it joins the rest at the party until you pull it back to idle for landing and taxi.   I just had this problem.  Mine was a but more severe where cylinders 5 and 6 would not participate during idle when it was cold.  I found a massive intake leak at the balance tube to intake riser joint (Continental thing)

Your IO360 should purr in the idle, if it doesn't there's a problem.  I chased an erratic idle for three years in my Mooney. Turned out to be an airframe-side fuel leak... but I digress....

My suggestion is to do Savvy's intake leak flight test profile.  I bet you will find you find one or more intake leaks.  I had repeated problems with intake gaskets until I coated them with Permatex #3 aviation sealer.  That finally did the trick.

 

Edited by Guitarmaster
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1 hour ago, Guitarmaster said:

Your IO360 should purr in the idle, if it doesn't there's a problem.  I chased an erratic idle for three years in my Mooney. Turned out to be an airframe-side fuel leak... but I digress....

According to Don Maxwell, the IO-360 should have a distinctive "loping" rhythm at idle because of the sniffle valve in the intake manifold.  I'm not sure what "loping" means, but mine definitely doesn't "purr..."

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17 minutes ago, jaylw314 said:

According to Don Maxwell, the IO-360 should have a distinctive "loping" rhythm at idle because of the sniffle valve in the intake manifold.  I'm not sure what "loping" means, but mine definitely doesn't "purr..."

I know some have a rhythmic lope to them, but mine was just erratic.  Once the fuel leak (leaking fuel strainer) was fixed, she idled very smooth. 

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2 hours ago, Guitarmaster said:

Your IO360 should purr in the idle, if it doesn't there's a problem.  I chased an erratic idle for three years in my Mooney. Turned out to be an airframe-side fuel leak... but I digress....

My suggestion is to do Savvy's intake leak flight test profile.  I bet you will find you find one or more intake leaks.  I had repeated problems with intake gaskets until I coated them with Permatex #3 aviation sealer.  That finally did the trick.

 

I did all the flying yesterday with ANR off, and didn't hear or feel any roughness or erraticness (?) in the idle. I'm not sure I'd call it purring or loping, but it didn't seem in any way out of the ordinary to me.

But I'm adding the Induction Leak Test (assuming that's what you meant; https://www.savvyanalysis.com/articles/in-flight-diagnostics ) to my next flight, thanks! Can't hurt.

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This is what a partially plugged injector looks like.  This is an IO360.  It caught my attention flying home one night when the EGT jumped  and the CHT decreased together for no apparent reason.
When I pulled the injector out, I found the tiniest particle of something in the injector.  Cleaned it out and it cleared right up.

https://www.savvyanalysis.com/flight/2430228/25d50e01-a31c-48ee-a33b-2b02c03e9b7e

The event starts around 22:40

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Do you have an in-line fuel filter next to the gascslator?

Do the fuel tanks vent properly?

What were your egts prior to them reading high?

I would still have an outside accessory shop look at the servo. I don’t trust precision. 

You’ve had a ton of fuel related issues and I’m thinking it might be the airplane. See if the fuel selector is leaking by trying to shut down with the selector itself. 

-Matt

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Okay, did another diagnostics flight. Uploaded it to Savvy and crossing my fingers Paul can get to it before the long weekend. Have some time booked with my A&P next week.
https://savvyanalysis.com/flight/3188152/aa0f2851-beff-485c-b05d-2d2fa7389b02

Run-up ignition system ("mag") check (L/B/R/B, 20 seconds each):    6:56-8:12vionics on at 02:56:00Z.

Take-off fuel pressure was 27 PSI, fuel flow in the mid-15s, RPMs were below 2650 until just a smidge at the very end (about 23:52), which I think was just my putting the nose down to level off. So, good news, I probably can safely adjust it +50 RPM safely, and get into the high 2600s without risking an overspeed.

GAMI test conducted at 7500' (leveled off and set power starting about 24:00), 21.9" MAP, 2400 RPM, 65% power as indicated by EDM-830, 13.8 gph full rich.

GAMI lean 1: 26:24 - 29:04
Enrichen:    29:04 - 31:20
GAMI Lean 2: 31:20 - 34:48
Enrichen:    34:48 - 38:08
GAMI lean 3: 39:04 - 41:44

Ignition stress test ("smooth" (no roughness) on both L and R) (B/L/B/R/B >30 seconds each):
Both:    41:36 - 42:24
Left:    42:24 - 43:00
Both:    43:00 - 44:08
Right:   44:08 - 44:56
Both:    44:56 - 45:52

Induction leak test done at 5,000' 24.1" 2550 RPM, then 14.1" 2550 RPM:
Leveled off at 5,000' at 49:44
Full rich at 50:56
WOT (24.1"):     50:00 - 51:36
10" MAP Reduced: 52:32 - 53:04

(at which point ATC needed me to descend for traffic so I ended the test).

Flew the RNAV LPV approach for 29R.

Post-flight idle check (850 rpm at 2 gph full rich):

1:05:20 - 1:08:00 (1:07:52 was where the engine started to stumble and threaten to cut out).

(Paul recommended I try this check when the plane was post-flight warm. Clearly it's way out of spec; idle is way too high, and idle mixture is way, way too rich.)

After that, just a mile long taxi back to the hangar.

Sigh. Does this stuff get easier? Less expensive? Ever? (More and more, renting a clapped out, threadbare Arrow for $195/hr is seeming like not such a bad option... :( )

Edited by chrixxer
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Looking again a day later...

1) EGT1 and CHT1 are staying colder than the other three cylinders... that’s two sensors saying the same thing...  possibly extra fuel feeding this FI...

2) Looks like a learning procedure was followed early in flight... three cylinders go to peak and come down... flight continues.... E4 also goes to peak, and never comes down... in fact it continues to creep higher...

I’m a fan of the data more than the video....  As PIC you know when you switch mags... while watching the EGTs rise... trying to watch two things at once.... hand and response... has become too challenging for me to follow along...

I can barely see the graph do anything...  my older JPI 700shows 6 bars that grow and peak, the decline and bottom... very easy to follow along...

Might just be camera angle...

Unfortunately, I didn’t see the expected effects of plugs going off line...

 

It would help for the next one to follow a procedure step by step...  the added steps take away from understanding what you did...

three mag tests causes confusion... unless you say.. ‘i’m Doing three mag tests’....

 

peaks in flight... ‘ I leaned 50°F ROP’  ‘ I used the ship’s gauge for leaning...’

It is a lot of work....

But even more work to try to figure things out... 

Expecting a mechanic to figure things out for you can get even more challenging.... or more expensive.... and frustrating for the owner...

 

I like to focus on one step at a time...

If looking for bad plugs... they show up in mag tests...if they don’t show up.... they aren’t bad enough...

if looking for bad fuel injectors.... they show up using a Gami spread...  the JPI is great for this... E4 never reached peak in this particular flight... ?

Summary... 

  • Something seems to be making E1 act cold.... and not because of TC placement....  
  • Something caused E4 to peak and stay there for the flight...
  • Following a tight plan will make the next data set easier to review... share the plan.
  • Annotating is especially helpful...
  • What leaning method are you using? What instrument(s) did you watch... how long did it take?

PP thoughts only not a mechanic...

Best regards,

-a-

 

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Chrix,

You got a head of me on this one, by a few minutes...

New data is much easier to follow.... great notes to go with that!

The mag test on the ground isn’t showing what I hoped to see...

  • two identical peaks...
  • it looks like three... and none are identical.  Like the two mags are not working the same... or the procedure isn’t the same... or both....

E1 still behaving colder than the rest...

How do you feel about the Gami lean tests? Did you get anything from that?

The Gami test typically is a lean through peak and keep leaning until you come out the other side on all cylinders... this seems to show two peaks. You may have caught the data... FF at peak for each cylinder...  but it isn’t easy to see in the graph if you smoothly leaned in one direction or moved the mixture back and forth...

The in flight mag test is definitely showing an anomaly...  expecting to see two identical peaks with all EGTs nicely overlaid..... look at the first mag test (L) and compare to the next...  the odd cylinders are showing cold EGTs on the left mag...

Do you see what I am seeing?  It is possible that I mixed up cyl numbers and mags...  takes a lot of memory to write about this stuff...

The good news... you are getting much better at reporting what is going on...  and it looks like one mag is not behaving very well compared to the other...

What would cause the odd cylinder EGTs to not peak as much as the even cylinders... on the L mag test...

E1 continues to show cold behavior... possibility of more FF going to that FI...

E4 continues to not lean like the others... not going past peak as the other three do...

I can take screen shots of the close-ups of each step discussed here... if that will help...

PP thoughts at the end of the evening....

-a-

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The RPMS jumps around +/-50 RPMs, are you feeling that?

I would not worry about absolute EGT temps.

You mags seem like they are timed differently.

I would do baby jar test and in addition to checking flow is the same, also carefully check output.

You were leaning a little too quickly, you need to do it very slowly, so EGTs don’t lag.

 

Tom

 

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If there is more FF going to one or more cylinders, I would expect a large spread in EGT peaks, I don’t see that.

Here is mine when 1&2 and 3&4 were running different mixtures:

554ed0f90c4a17b50840fb9dc3e5b88e.jpg

 

I’m no expert and didn’t study it in great detail, so I will defer to those who more experience.

 

Tom

 

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9 hours ago, chrixxer said:

Sigh. Does this stuff get easier? Less expensive? Ever? (More and more, renting a clapped out, threadbare Arrow for $195/hr is seeming like not such a bad option... :( )

It does get easier, but it never goes away, just ebbs and flows.  If you buy a vintage plane from an owner that was not mechanically inclined/aware (god forbid also a CB), then you are buying from someone who doesn't know what they don't know.  The quality of the mx is entirely up to an A&P that does not fly the airplane.  That A&P is in a tough position.  You're here, you're getting good advice and you're learning more about what keeps these planes safe and in the sky.  I think that all of the challenges you've faced will make you a much more savvy operator in the long run.  When I became partners in my aircraft it took one annual to make it airworthy, but years to find all of the minor things that needed to be corrected to make it the fine flying (it's not a looker but it flies beautifully) plane that it is today.  It still has minor squawks (non airworthiness issues) but they are known and there is a plan to address them.  You are thoroughly trouble shooting issues that probably would have gone unnoticed by pilots a few decades ago.  This process will make you way more perceptive of the operational condition of this plane and any that you fly in the future.  This will make you a better pilot/operator.

Edited by Shadrach
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29 minutes ago, Shadrach said:

It does get easier, but it never goes away, just ebbs and flows.  If you by a vintage plane from an owner that was not mechanically inclined/aware (god forbid also a CB), then you are buying from someone who doesn't know what they don't know.  The quality of the mx is entirely up to an A&P that does not fly the airplane.  That A&P is in a tough position.  You're here, you're getting good advice and you're learning more about what keeps these planes safe and in the sky.  I think that all of the challenges you've faced will make you a much more savvy operator in the long run.  When I became partners in my aircraft it took one annual to make it airworthy, but years to find all of the minor things that needed to be corrected to make it the fine flying (it's not a looker but it flies beautifully) plane that it is today.  It still has minor squawks (non airworthiness issues) but they are known and there is a plan to address them.  You are thoroughly trouble shooting issues that probably would have gone unnoticed by pilots a few decades ago.  This process will make you way more perceptive of the operational condition of this plane and any that you fly in the future.  This will make you a better pilot/operator.

To add on to what Ross says, you are making this the plane you wish it was when you bought it. There is always a larger expense catching up on deferred maintenance, but it does get better over time. You will come out of this with a solid plane where you know every vibration that should and should not be there when you fly it, and knowing that will help reduce your costs since problems get addressed before they get out of hand.

I was fortunate my J had a lot of loving, corporate care for the majority of its life, and then two owners who also took care of problems as they were found. Doesn't mean there was nothing wrong with it when I bought it, but nothing airworthy or expensive was in need of repair. Now, I get to do upgrades and updates to her as long as I keep the age-related items under control.

Yours will get to that point as well. You are doing a good job and soaking up more knowledge than many people. It will all pay off.

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The RPMS jumps around +/-50 RPMs, are you feeling that?
I would not worry about absolute EGT temps.
You mags seem like they are timed differently.
I would do baby jar test and in addition to checking flow is the same, also carefully check output.
You were leaning a little too quickly, you need to do it very slowly, so EGTs don’t lag.
 
Tom
 

Yeah, RPMs often hunt a tiny bit. When I’m not mucking with other settings, it fluctuates maybe +/- 10 rpm in cruise. I just assumed that was the extra precision of digital vs 50 year old mechanical tach.

We’ll check mag timing and do the baby jar test, hopefully next week. Both Paul and my A&P want to get the prop governor adjusted before I dive into FF issues though.

The Savvy flight profiles call for a 3-4 minute lean, which I was doing for the GAMI sweeps (had a stopwatch running). It’s a challenge with the quadrant power controls, to do it slowly and steady enough to not be “too quick,” but not so slowly that the JPI interprets a false peak and shifts into icicle mode prematurely...


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2 hours ago, chrixxer said:

The Savvy flight profiles call for a 3-4 minute lean, which I was doing for the GAMI sweeps (had a stopwatch running). It’s a challenge with the quadrant power controls, to do it slowly and steady enough to not be “too quick,” but not so slowly that the JPI interprets a false peak and shifts into icicle mode prematurely...

There's no reason to put the JPI into lean-find mode for the GAMI sweeps.  You're going to be reviewing the data after the fact anyway, and having the display abruptly change is another distraction.  You can just put it in normalize mode when you're near peak, and you'll be able to see when all the bars are coming down since it's more sensitive

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15 minutes ago, bradp said:

You had your original piece of baffle in the FF servo or induction I can’t remember ... 

A&P reported he found it in the fuel servo. Not sure "baffle" is right; it was the lower part of the gasket that seals the ram air intake door.

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