High EGTs on one cylinder

[Raptortail]

As background, I have a 1993 Bravo TLS and over the summer of '24 we replaced cylinder #1.  For 6mo, the cylinder was fine but in January, the EGTs on cylinder #1 dropped off to 180 deg on takeoff and climbout while the other cylinders were at a normal ~1360 deg.   I put the plane in the shop and the A/P cleaned the spark plugs and says he fixed an intake leak that caused the issue.  I then had two good flights and now on climbout over the weekend, the EGT on cylinder 1 was consistently 200 deg higher than the next highest cylinder.   However, once in cruise, the EGT1 came back into normal range with the other cylinders.   I repeated this result on a high-speed taxi down the runway on another day.

My guess is its either a fouled spark plug (unlikely because the AP just cleaned them a month ago with the last EGT drop issue) or a fuel injector clog (the AP also supposedly cleaned the injector last month too).  CHTs on cylinder 1 were the second highest at 402 deg but not excessively high.  

My question is whether I should be concerned enough not to fly it because of high EGTs on one cylinder or if its safe to fly to another airport were my primary AP is located?  What would be the risks or any other thoughts on what the issue could be?  Thanks,

[hammdo]

Have you swapped probes to see if the high EGTs go with the probe? That is also a possibility the probe may be defective. Also a resistance check on the plug would be another check.

-Don

[Rick Junkin]

7 hours ago, Raptortail said:

As background, I have a 1993 Bravo TLS and over the summer of '24 we replaced cylinder #1.  For 6mo, the cylinder was fine but in January, the EGTs on cylinder #1 dropped off to 180 deg on takeoff and climbout while the other cylinders were at a normal ~1360 deg.   I put the plane in the shop and the A/P cleaned the spark plugs and says he fixed an intake leak that caused the issue.  I then had two good flights and now on climbout over the weekend, the EGT on cylinder 1 was consistently 200 deg higher than the next highest cylinder.   However, once in cruise, the EGT1 came back into normal range with the other cylinders.   I repeated this result on a high-speed taxi down the runway on another day.

My guess is its either a fouled spark plug (unlikely because the AP just cleaned them a month ago with the last EGT drop issue) or a fuel injector clog (the AP also supposedly cleaned the injector last month too).  CHTs on cylinder 1 were the second highest at 402 deg but not excessively high.  

My question is whether I should be concerned enough not to fly it because of high EGTs on one cylinder or if its safe to fly to another airport were my primary AP is located?  What would be the risks or any other thoughts on what the issue could be?  Thanks,

Your #1 CHT is out of phase with the rest of the cylinders so I don't think you have an EGT or CHT probe issue. There's something happening at full power on #1 that resolves at cruise power. 1748dF EGT is troubling, and implies either a too lean mixture or a bad plug. Since the problem resolves at cruise power and the fuel side has been checked I'd look at both #1 plugs. An extended runup check at a lean mixture might show you if one of the plugs is dropping out. Otherwise pulling them both and checking that resistance is <4K ohms as has been suggested might show which plug is bad, if either is.

What plugs are you running?

Cheers,
Rick

[Fly Boomer]

1 minute ago, Rick Junkin said:

Your #1 CHT is out of phase with the rest of the cylinders so I don't think you have an EGT or CHT probe issue. There's something happening at full power on #1 that resolves at cruise power. 1748dFEGT is troubling, and implies either a too lean mixture or a bad plug. Since the problem resolves at cruise power and the fuel side has been checked I'd look at both #1 plugs. An extended runup check at a lean mixture might show you if one of the plugs is dropping out. Otherwise pulling them both and checking that resistance is >4K ohms as has been suggested might show which plug is bad, if either is.

What plugs are you running?

Cheers,
Rick

Do you mean <4K ohms?

[Rick Junkin]

3 minutes ago, Fly Boomer said:

Do you mean <4K ohms?

Thanks for catching that, my bad. Yes. <4K ohms. I corrected my original post.

 

[Rick Junkin]

8 hours ago, Raptortail said:

For 6mo, the cylinder was fine but in January, the EGTs on cylinder #1 dropped off to 180 deg on takeoff and climbout while the other cylinders were at a normal ~1360 deg.

For clarification, did #1 EGT drop TO 180dF, or drop BY 180dF? If it dropped TO 180dF then you lost all combustion in #1 and that most likely points to faulty ignition. I would suspect you felt some roughness in the engine if this is the case.

[Raptortail]

Yes, back in January, cylinder #1 EGT dropped TO 180dF at full power on takeoff and climb-out.  At the point that it happened I had run out of runway and kept climbing.  I definitely lost some power and the engine didn't sound normal so I limped tightly around the pattern and landed with no incident.  The A/P on the field looked at it a few weeks later and said I had an induction leak and he cleaned the spark plugs.  I got two good flights out of it before this opposite problem of the EGT's being 200dF higher than the other cylinders on climb-out. 

I agree with some of the comments that it seems to be a lean mixture issue.  I'm waiting on the A/P on the field to get to me but I will make sure he re-checks the plugs (Champion - RHB37E Massive plugs) and also cleans out the fuel injector.   My guess is this isn't a probe issue but we can certainly try to swap them with another cylinder if we need to.

I would prefer to take the plane to my primary A/P about 30 miles away.  Thoughts on whether you would fly it in this condition?  There is no published limitation on EGT temp like there is CHT or TIT so as long as CHT and TIT are within reasonable range, would you fly?

[Slick Nick]

It depends what's causing the issue. If it's an air leak, what's to say it doesn't suddenly get worse on your 30 mile flight and cook the cylinder? If there's a way for you to "limp" it there at a reduced power setting that may be advantageous.

[hammdo]

Question, do you have backup vacuum system for steam gauges? Just ruling that out - sometimes they hook those up to an intake tube…

-Don

[Raptortail]

2 minutes ago, hammdo said:

Question, do you have backup vacuum system for steam gauges? Just ruling that out - sometimes they hook those up to an intake tube…

-Don

No, vacuum pump is gone and I am all digital (Garmin GI-275 ADI, HSI, ESI).  For good measure, I'll mention that we did keep the analog Airspeed, vertical speed, altimeter and turn coordinator to maintain the more traditional 6-pack look and feel.  Its a great mix of old and new.   

[IvanP]

I would start with the fuel injector. Partially clogged injector will cause lean mixture and higher EGTs. Also, borescoping the cylinder may be a good idea to see if there are any signs of damge to valves. I woudl not fly in its present condition.  

[Raptortail]

2 hours ago, IvanP said:

I would start with the fuel injector. Partially clogged injector will cause lean mixture and higher EGTs. Also, borescoping the cylinder may be a good idea to see if there are any signs of damge to valves. I woudl not fly in its present condition.  

Good thoughts and thanks for the advice.