The $9k annual (and counting) with not much to show...

tawood said:
In a nut shell: number 3 cylinder EGT is up to 250 degrees hotter than the rest...any attempts to lean the engine immediately causes bad miss (presumably from number 3 cylinder). Altitude exacerbates the problem (which seems opposite to me). I don't have a cylinder head temp gauge, but oil temp stays normal.



Probes and gauge swapped and high EGT still present.
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How did the "compression" number of cylinder 3 compare to the others? If it was lower, could it not be a leaking exhaust valve?

If the exhaust valve is leaking, it can allow still-burning mixture into the pipe and drive the EGT value up.

Tim
 
tawood said:
In a nut shell: number 3 cylinder EGT is up to 250 degrees hotter than the rest...any attempts to lean the engine immediately causes bad miss (presumably from number 3 cylinder). Altitude exacerbates the problem (which seems opposite to me). I don't have a cylinder head temp gauge, but oil temp stays normal
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I guess the first thing I would do is swap #3 for #1 and see if the problem follows, thus taking the engine out of the equation...
 
Troska said:
How did the "compression" number of cylinder 3 compare to the others? If it was lower, could it not be a leaking exhaust valve?

If the exhaust valve is leaking, it can allow still-burning mixture into the pipe and drive the EGT value up.

Tim
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I don't remember exactly but all were very good...like 74 75 75 74 / 80 good.
 
tawood said:
For the IFR cert: EVERY SINGLE pitot related part replaced: airspeed indicator, VSI, Alt, new tubing, new pitot. Finally passed.
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Say what?

91.411 IFR certification requires the static system, altimeter, and altitude encoder to be inspected. The airspeed indicator and pitot system are not part of it.

A VSI is not even required equipment for IFR so how could there possibly be a requirement to inspect and replace it?

---

On another note, as someone else said, no such thing as "high EGT".
 
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Takes what, 2 hours, to swap cylinders 1 and 3? That'll tell you immediately if you must look inside or outside the engine.
 
dmspilot said:
Say what?

91.411 IFR certification requires the static system, altimeter, and altitude encoder to be inspected. The airspeed indicator and pitot system are not part of it.

A VSI is not even required equipment for IFR so how could there possibly be a requirement to inspect and replace it?

---

On another note, as someone else said, no such thing as "high EGT".
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Based on OP's avatar, he's got a Cherokee. On the Cherokee, the static port is on the back of the pitot mast, which could explain why a new pitot mast was required. The both the ASI and VSI have static inputs. If those were failing/leaking, the static system would leak. Only way to fix that leak in the static system is to replace the offending gauges.
 
Not sure what kind of interference problem you are having but I just worked with an Avionics guy and owner to figure out an interference problem on a Cherokee.

The issue was a new Garmin Comm radio, Antenna Cable, and Antenna were installed.
It worked great until we flew over to the local Class C airspace (Boise), Then the squelch would break and we would hear static all the time.
Seemed to only happen on weekends and within about 3 miles of the airport, but not on the ground. We would turn the squelch all the way up on the radio and it would still do this.

Troubleshooting was difficult because we had to fly on weekdays to test it.
Obviously there is some sort of equipment near Boise that only runs during business hours on weekdays that is generating additional radio noise. But other aircraft with the exact same radio do not have this issue. In fact we tried swapping another radio to confirm it wasn't the radio itself.

After several calls to Garmin, and additional troubleshooting we determined that it is something about the ELT or ELT antenna causing it. At this point we know that disconnecting the ELT antenna will eliminate this noise. Garmin essentially said "something re-radiating the signal in the airplane"

Just something to possibly check.

Brian
 
He swapped the cylinders, or the sensors?
 
Ryanb said:
More than likely he would, or at least take a good shot at it.

He's an experienced mechanic, but most folks on here like to discount it, and his abilities.
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Most don't discount his abilities. Rather discount his "conversation" style. I rarely come across someone who constantly answers a question with another question like Tom does. As though he expects the person making the original query to know as much and have seen as much as he has. If they did have his knowledge and experience they probably wouldn't bother asking.
 
weirdjim said:
I wasn't aware that Tom had passed away. Is that true?

Jim
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I believe he went on a driving vacation. To Canada.
That's the same thing isn't it. :rolleyes:

Rumor has it he hit a beaver...

images


or maybe it was a bear...
images
 
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GRG55 said:
Most don't discount his abilities. Rather discount his "conversation" style. I rarely come across someone who constantly answers a question with another question like Tom does. As though he expects the person making the original query to know as much and have seen as much as he has. If they did have his knowledge and experience they probably wouldn't bother asking.
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Most might not, but I've seen a fair number of posts in the past discrediting his knowledge and work he's performed. Some on here act like they know more than he does and they're not even A&P's.

I imagine the brash tone that is noticed in some of his posts, are a result of the years he's spent in the Navy.

weirdjim said:
I wasn't aware that Tom had passed away. Is that true?

Jim
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No it's not.
 
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If the problem did not follow the sensor probe there are only a limited number of potential issues:
1. Fuel
2. Air
3. Combustion chamber
4. Ignition

You have three basic symptoms:
1. EGT has risen from previous values
2. Engine sounds/feels like it is miss-firing when you lean
3. Problem is worse as you gain altitude

Here are the possible scenarios I can think of:
  • If the ignition timing is delayed you will get a higher EGT. Unless this is combined with another problem, I do not see how this can cause the second symptom.
  • Fuel constrained in some manor (think of debris in the line). The cylinder may be running at peak or close by not having enough fuel. As you lean the fuel flow, suddenly there is insufficient fuel and you start to get miss fires. From what I recall a Lycoming carburetor is adjusting mixture based on altitude; if that is the case you it would get worse as you climb since the engine is getting progressively leaner.
  • Air flow restriction from the carb to cylinder. This can make the cylinder supper rich, and cause a delayed flame front. This matches the first symptom. However, the engine will fire more smoothly and not miss when you lean it. That means the second and likely the third symptom do not apply.
  • Ignition system has become delayed too far, specifically for this cylinder. Depending on where you are in terms of ROP/LOP and how delayed you can match the symptoms. If delayed by a few degrees, the EGT will rise. This is caused by not all the fuel being fully com-busted in the expansion stroke. As you lean the engine, until you are significantly LOP, you increase the speed of the flame front. This can cause the engine to run rough and feel like a miss fire, as the expansion of the flame front runs over the bottom dead center and continues to push on the piston before the exhaust value releases the pressure. The same situation works as you climb in altitude.

I am sure there is more. The timing from what I understand can be measured by turning the prop by hand with the spark plugs removed and see when they fire (from what I have been told remove all of them, something about the compression and back firing). Using any one of the digital timers on the prop will be more accurate then depending on the marks on the gears. For the fuel constraint you need to ask the mechanic. I know the standard answer for a fuel injected engine.

Note, usual disclaimers apply: I am not a mechanic, I just listen to them a fair amount. So run this by someone who actually knows this stuff.

Tim
 
Have you swapped spark plugs between cylinders?
 
I'm glad I have a very smart and very honest mechanic. I always feel bad because he does not charge enough. I guess that is why he is always backlogged several months.
 
Some update...my mechanic admits there is something wrong, but also admits he can't figure it out and has no more things to try. Anyone know a good o-320 mechanic in the SE Michigan area? I'm going to start calling around today.

And a note on those saying "no such thing as high EGT"...I agree, and perhaps I wasn't clear. What I am seeing is "abnormally high EGT"...or "Peak EGT without / before leaning".
 
Checkout_my_Six said:
what happens when you do lean?.....does it peak early?
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It starts to run rough...the other cylinders egt climb/peak while #3 at first stays at peak (it runs at full rich with #3 at the egt point where the others peak), then drops off.
 
could be cracked somewhere....I'd pressurize it and spray soapy water on the outside and look for bubbles.
 
tawood said:
I need to vent...

I also had requested they look into a interference problem with my Comm 1 KX155 caused by my JPI fuel flow meter.
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brcase said:
The issue was a new Garmin Comm radio, Antenna Cable, and Antenna were installed.
It worked great until we flew over to the local Class C airspace (Boise), Then the squelch would break and we would hear static all the time.

After several calls to Garmin, and additional troubleshooting we determined that it is something about the ELT or ELT antenna causing it. At this point we know that disconnecting the ELT antenna will eliminate this noise. Garmin essentially said "something re-radiating the signal in the airplane"
Click to expand...

I had this exact issue with a KX-155 and Garmin setup and suffered like Brian (new antennas, new coax all the way to them, another few hours replacing wires that were supposedly not shielded correctly). Upon return each time, same squelch break. Also had the recommended ELT interference suggestion, and logged the ELT inop, had it removed and flew with it completely out of the plane locally ... still the same problem.

I had about given up ... had a non-avionics mechanic tell me to have them check the on/off volume knob on the KX-155 as they wear and start moving slightly from pilots adjusting them during turbulence. Sent the unit in for refurb, they said the knob had a "little play" changed the volume knob on the unit .... and squelch breakthrough is now gone. It makes absolutely no sense and I'm sure someone will call BS as that breakthrough was occurring across Com1 and Com2. After having gone through all the above, I know what the original poster is suffering and didn't care if they fixed it by exorcism, voodoo/chicken blood etc.

Had a similar nightmare with a different issue mechanically. That one was solved finding a better mechanic that didn't just throw parts at problems and actually diagnosed issues.
 
Oh my...,get your plane away from this guy. And go quickly. Crazy to read this.
 
9k on a cherokee 140. Some folks just don't know when to fold 'em, and I don't even play poker...
 
The engine runs fine, but one cylinder always peaks later than the others. How much later? I know you said this is a new problem however this is definitely not unusual for a carb engine...
 
Prime the **** out of it and look for any leaks in the primer lines. He may or may not have sprayed those while looking for leaks during his checking of the intake system.

Its acts more cylinder issues, showed up suddenly and nothing found.
 
is this a four channel egt or a single channel with a rotary switch to change probe? if it is a rotary switch change the #3 probe to a different position and check to see if its a switch problem. same with 4 channel EGT. hook probe 3 to a different position to make sure its not a indicator problem.

bob
 
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