Engine drops a cylinder. Head Scratcher. AFP?

[Kahuna]

Need ideas for troublshooting.
IO-540, AFP.

Symptom,
Below 1500 RPM, #2 cylinder drops cold. Misses, no EGT, CHT drops.
~1500rpm, cylinder comes back alive, but is running ~100degF egt hotter than normal/others. Leaning it shows the cylinder continues to lean and peaks early indicating cylinder is lean. Mag checks good.

Bring RPM up higher ~2000rpm and the cylinder functions normally. EGT in line with others. Mag checks function as expected.

Actions so far.
1. Compression check hot and cold GOOD. 78/90
2. Swap injectors, swap injector lines around. Problem stays with the one cylinder. (I though for sure plugged injector.
3. Rockers snug, nothing unusual under rocker cover.
4. Oil change, filter clean.
5. Plugs look good.
6. Intake tube tight. No sign of leaks at cylinder or sump
7. Cylinder inspection superficial scan all around it looks good.

Ideas from the brainiacs?
THanks

[JonJay]

My buddy had a similar symptom but it moved around from time to time to different cylinders. After hours of agonizing troubleshooting he found a few small pieces of material floating around in the Distributor.
Worth a shot.

[Don at Airflow]

Check the fuel distribution of the flow divider by doing the bottle check. If you don't know how to do this give me a call.

Don

[AltonD]

Originally Posted by Kahuna

Need ideas for troublshooting.
IO-540, AFP.

Symptom,
Below 1500 RPM, #2 cylinder drops cold. Misses, no EGT, CHT drops.
~1500rpm, cylinder comes back alive, but is running ~100degF egt hotter than normal/others. Leaning it shows the cylinder continues to lean and peaks early indicating cylinder is lean. Mag checks good.

Bring RPM up higher ~2000rpm and the cylinder functions normally. EGT in line with others. Mag checks function as expected.

Actions so far.
1. Compression check hot and cold GOOD. 78/90
2. Swap injectors, swap injector lines around. Problem stays with the one cylinder. (I though for sure plugged injector.
3. Rockers snug, nothing unusual under rocker cover.
4. Oil change, filter clean.
5. Plugs look good.
6. Intake tube tight. No sign of leaks at cylinder or sump
7. Cylinder inspection superficial scan all around it looks good.

Ideas from the brainiacs?
THanks

We saw this exact thing on an angle valve IO360. It was the #3 cylinder. It turned out to be the #2 cylinder intake. The o-ring on the intake tube was letting in air. How this affected the #3 cylinder, who knows. repaired the tube, problem gone.

[mahlon_r]

Sounds like an induction leak on number two cylinder intake system. Classic intake/ induction leak symptoms! Double check the pipes especially if the lip under the flange is cracked and also that the non used 1/8 pipe plug in the cylinder intake port.
When the suction is high, in that cylinder?s intake system, as it gets as you go to lower RPM and power, something is killing that cylinder. Either you are sucking in outside air or you are getting more fuel then you should have. Maybe a partially restricted FI nozzle vent that allows more fuel at high suction??
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

[Kahuna]

I also am leaning towards an intake leak. Your right. Classicsymptoms.
Ill check the tube and npt port.

Ill check it and report back.

[Kahuna]

Originally Posted by Don at Airflow

Check the fuel distribution of the flow divider by doing the bottle check. If you don't know how to do this give me a call.

Don

I figured that since I hooked up the line to a different port off the flow divider, that would be ruled out.

I do have my test jars though. Easy enough to try.

[jthocker]

For crying out loud Mike, you've got 6 cylinders! Most of us make do with just 4!
No sympathy!

Mutha

[Kahuna]

Was the intake gasket. Brittle and wore out.
Thanks for the responses guys.
Best,

[AZtailwind]

Originally Posted by jthocker

For crying out loud Mike, you've got 6 cylinders! Most of us make do with just 4!:

That right! make #1 leak and you'll be back with us
easy find, glad to hear