So after four overhauled cylinders installed with new pistons and rings, my airplane doesn't run the best. I recently let the resident AP/IA who I share a hangar with have a crack at the Cherokee. He's a Charles Taylor award winner and been around a long, long time.
He borescoped the cylinders and said the pistons and bores look good other than small amounts of some strange dark honey like bubbles of crap near the top of the bore and a little bit on one of the pistons that he had never seen before. He cleaned and tested spark plugs. Checked spark plug leads. Decided that the right mag needed to be tested (it needed to be cleaned and the points retimed, they were off pretty badly). We took the cowlings off, and I installed a 3" KN air filter that I keep around for ground running. After reinstalling the magneto he suspected of having problems (that the shop cleaned and retimed due to the points being out of time), we fired it up. Fixed an air leak around the intake tube gasket. Adjusted the mixture. Got the idle down to 650. Seems to be running pretty good. Mag check is ok. Tried a full power static runup and it pulls 2340 RPM. We eliminated the cough that we would get whenever we pull the throttle back, and it's now running smooth other than an occasional little hiccup. So we put it back in the hangar, put the cowlings back on, he signs it off, and we call it done.
Fast forward two weeks. Instructor gets back into town so we go to do some flying. Airplane starts right up on the second blade. But runs a little rough. And the warmer it gets, the more obvious it is. We motor on out to a clear area of the ramp and do a 2000 RPM mag check. Mag drop is only 75 RPM, and it runs the same on either mag. Static RPM - 2340. But has a definite miss, and now it doesn't want to idle like it did before......it's slower and rough. And occasionally there's a hard "kick" in the rudder pedals.
Lastly, #3 cylinder which has shown cooler readings in the past, is dropping from 950 at idle, to 425 ish at full throttle. I'm going to install an alternate EGT sender and gauge to see if this is a solid reading or a wiring harness or gauge issue.
The only difference since the mechanic tuned it up, is that with the cowlings on, the engine is now running off the cowling air duct and air filter. I have a Brackett oiled foam filter, the oil on these is really strange and gooey. Do these break down or shed and cause problems? I'm planning to pull and check it tonight.
And I also checked out the engine mount looking for issues.....the lower right Lord mount looks to be collapsed......like the engine is sagging on the mount and smooshing the rubber insulator. None of the others look like this. I think this is why we are feeling a lot of roughness in the airframe. If it's visibly sagging, it's junk, correct?
I'm going to inspect the air filter, and verify the EGTs on that #3 cylinder one more time, then have a heart to heart with the guy who did the top overhaul for me.......
Thanks in advance for any ideas....
He borescoped the cylinders and said the pistons and bores look good other than small amounts of some strange dark honey like bubbles of crap near the top of the bore and a little bit on one of the pistons that he had never seen before. He cleaned and tested spark plugs. Checked spark plug leads. Decided that the right mag needed to be tested (it needed to be cleaned and the points retimed, they were off pretty badly). We took the cowlings off, and I installed a 3" KN air filter that I keep around for ground running. After reinstalling the magneto he suspected of having problems (that the shop cleaned and retimed due to the points being out of time), we fired it up. Fixed an air leak around the intake tube gasket. Adjusted the mixture. Got the idle down to 650. Seems to be running pretty good. Mag check is ok. Tried a full power static runup and it pulls 2340 RPM. We eliminated the cough that we would get whenever we pull the throttle back, and it's now running smooth other than an occasional little hiccup. So we put it back in the hangar, put the cowlings back on, he signs it off, and we call it done.
Fast forward two weeks. Instructor gets back into town so we go to do some flying. Airplane starts right up on the second blade. But runs a little rough. And the warmer it gets, the more obvious it is. We motor on out to a clear area of the ramp and do a 2000 RPM mag check. Mag drop is only 75 RPM, and it runs the same on either mag. Static RPM - 2340. But has a definite miss, and now it doesn't want to idle like it did before......it's slower and rough. And occasionally there's a hard "kick" in the rudder pedals.
Lastly, #3 cylinder which has shown cooler readings in the past, is dropping from 950 at idle, to 425 ish at full throttle. I'm going to install an alternate EGT sender and gauge to see if this is a solid reading or a wiring harness or gauge issue.
The only difference since the mechanic tuned it up, is that with the cowlings on, the engine is now running off the cowling air duct and air filter. I have a Brackett oiled foam filter, the oil on these is really strange and gooey. Do these break down or shed and cause problems? I'm planning to pull and check it tonight.
And I also checked out the engine mount looking for issues.....the lower right Lord mount looks to be collapsed......like the engine is sagging on the mount and smooshing the rubber insulator. None of the others look like this. I think this is why we are feeling a lot of roughness in the airframe. If it's visibly sagging, it's junk, correct?
I'm going to inspect the air filter, and verify the EGTs on that #3 cylinder one more time, then have a heart to heart with the guy who did the top overhaul for me.......
Thanks in advance for any ideas....
