M20E for me Posted October 17, 2022 Report Posted October 17, 2022 On my M20E I'm having problems with the engine wanting to die when it has warmed up. The engine fires right up when cold and idles well, it is only after flying when I have the wanting to die problem. While reducing power for landing there is a lot of back firing and, once one the ground, I need to keep the RPMs above 1400 or the engine WILL die. I don't have a JPI monitor so I can't provide good engine data, this is going to be the first pieces of new avionics I install. I do, however, have an EGT monitor for each cylinder. To trouble shoot I took the plane up to 4000 feet while staying within landing distance of the airport and I cycled through the EGTs at various different power settings. I was thinking an induction leak which should give a higher EGT reading on the cylinder(s) that would have a leak. At all power settings the EGT was consistent across all of the cylinders with the exception of #2 which, was lower by around 200 degrees. At the lower power settings the readings were a bit closer but, #2 was always colder then the other three. Even on the ground after landing they were all close with the exception of #2 being a little colder. I have had all of the intake runner gaskets and O-rings replaced and still have the problem. When the #2 runner was removed the O-ring was split in two with one half laying inside the sump. I thought this was the smoking gun and my mechanic replaced it but the problem still exists. One thing of note is two of the intake runners have a different O-ring configuration than the other two; two are big thick O-rings and two have a much smaller cross section diameter, I read on this forum that can be typical? One thing I did noticed was the bores in the sump for the O-rings, while they are all smooth, they are not straight (if that makes sense). When I run my finger through the bore I can feel some waviness in the bore. my thought is maybe with the thermal expansion the intake runner moves to a position where the O-ring no longer creates a good seal and after the engine cools off it seals again? Any thoughts on where else there might be an induction leak or any thoughts on possible other culprits? Thanks! Scott
Ragsf15e Posted October 17, 2022 Report Posted October 17, 2022 53 minutes ago, M20E for me said: On my M20E I'm having problems with the engine wanting to die when it has warmed up. The engine fires right up when cold and idles well, it is only after flying when I have the wanting to die problem. While reducing power for landing there is a lot of back firing and, once one the ground, I need to keep the RPMs above 1400 or the engine WILL die. I don't have a JPI monitor so I can't provide good engine data, this is going to be the first pieces of new avionics I install. I do, however, have an EGT monitor for each cylinder. To trouble shoot I took the plane up to 4000 feet while staying within landing distance of the airport and I cycled through the EGTs at various different power settings. I was thinking an induction leak which should give a higher EGT reading on the cylinder(s) that would have a leak. At all power settings the EGT was consistent across all of the cylinders with the exception of #2 which, was lower by around 200 degrees. At the lower power settings the readings were a bit closer but, #2 was always colder then the other three. Even on the ground after landing they were all close with the exception of #2 being a little colder. I have had all of the intake runner gaskets and O-rings replaced and still have the problem. When the #2 runner was removed the O-ring was split in two with one half laying inside the sump. I thought this was the smoking gun and my mechanic replaced it but the problem still exists. One thing of note is two of the intake runners have a different O-ring configuration than the other two; two are big thick O-rings and two have a much smaller cross section diameter, I read on this forum that can be typical? One thing I did noticed was the bores in the sump for the O-rings, while they are all smooth, they are not straight (if that makes sense). When I run my finger through the bore I can feel some waviness in the bore. my thought is maybe with the thermal expansion the intake runner moves to a position where the O-ring no longer creates a good seal and after the engine cools off it seals again? Any thoughts on where else there might be an induction leak or any thoughts on possible other culprits? Thanks! Scott This isn’t perfect, but you can look at your lowest idle manifold pressure to help check for a intake leak. It depends on where the manifold pressure reading is taken from and where the leak is, but sometimes you may show a high manifold pressure on the ground at idle. Mine goes down to around 10 inches or so at idle.
Ragsf15e Posted October 17, 2022 Report Posted October 17, 2022 55 minutes ago, M20E for me said: On my M20E I'm having problems with the engine wanting to die when it has warmed up. The engine fires right up when cold and idles well, it is only after flying when I have the wanting to die problem. While reducing power for landing there is a lot of back firing and, once one the ground, I need to keep the RPMs above 1400 or the engine WILL die. I don't have a JPI monitor so I can't provide good engine data, this is going to be the first pieces of new avionics I install. I do, however, have an EGT monitor for each cylinder. To trouble shoot I took the plane up to 4000 feet while staying within landing distance of the airport and I cycled through the EGTs at various different power settings. I was thinking an induction leak which should give a higher EGT reading on the cylinder(s) that would have a leak. At all power settings the EGT was consistent across all of the cylinders with the exception of #2 which, was lower by around 200 degrees. At the lower power settings the readings were a bit closer but, #2 was always colder then the other three. Even on the ground after landing they were all close with the exception of #2 being a little colder. I have had all of the intake runner gaskets and O-rings replaced and still have the problem. When the #2 runner was removed the O-ring was split in two with one half laying inside the sump. I thought this was the smoking gun and my mechanic replaced it but the problem still exists. One thing of note is two of the intake runners have a different O-ring configuration than the other two; two are big thick O-rings and two have a much smaller cross section diameter, I read on this forum that can be typical? One thing I did noticed was the bores in the sump for the O-rings, while they are all smooth, they are not straight (if that makes sense). When I run my finger through the bore I can feel some waviness in the bore. my thought is maybe with the thermal expansion the intake runner moves to a position where the O-ring no longer creates a good seal and after the engine cools off it seals again? Any thoughts on where else there might be an induction leak or any thoughts on possible other culprits? Thanks! Scott Is the fuel pressure steady when it’s warm? Ever try the boost pump when it’s stumbling? There are places where you need good insulation on the fuel line fittings or they get hot and vaporize fuel in the line. Probably won’t happen with good cooling air or higher fuel flow while you’re flying, but on the ground? Maybe.
N201MKTurbo Posted October 17, 2022 Report Posted October 17, 2022 It sounds like you just need to adjust your idle mixture. Do it when the engine is hot. It sounds like it is very rich. When it is hot and doesn’t want to idle pull the mixture out a lot and see if there is a mixture setting where it will idle. 1
M20E for me Posted October 17, 2022 Author Report Posted October 17, 2022 I should have added that I have the same result with and with out the boost pump on. I'll check the manifold pressure this weekend. I do lean it out quite a bit while on the ground while taxing but, after landing, haven't been leaning it out because I'm just trying to keep the engine from dying. I'll give that a try as well.
M20F Posted October 17, 2022 Report Posted October 17, 2022 Has the plane ever run correctly? If it did when did the change in circumstances occur, what things occurred around the change, etc. When you had the A&P look at it what was their feedback.
Guest Posted October 17, 2022 Report Posted October 17, 2022 4 hours ago, M20E for me said: On my M20E I'm having problems with the engine wanting to die when it has warmed up. The engine fires right up when cold and idles well, it is only after flying when I have the wanting to die problem. While reducing power for landing there is a lot of back firing and, once one the ground, I need to keep the RPMs above 1400 or the engine WILL die. I don't have a JPI monitor so I can't provide good engine data, this is going to be the first pieces of new avionics I install. I do, however, have an EGT monitor for each cylinder. To trouble shoot I took the plane up to 4000 feet while staying within landing distance of the airport and I cycled through the EGTs at various different power settings. I was thinking an induction leak which should give a higher EGT reading on the cylinder(s) that would have a leak. At all power settings the EGT was consistent across all of the cylinders with the exception of #2 which, was lower by around 200 degrees. At the lower power settings the readings were a bit closer but, #2 was always colder then the other three. Even on the ground after landing they were all close with the exception of #2 being a little colder. I have had all of the intake runner gaskets and O-rings replaced and still have the problem. When the #2 runner was removed the O-ring was split in two with one half laying inside the sump. I thought this was the smoking gun and my mechanic replaced it but the problem still exists. One thing of note is two of the intake runners have a different O-ring configuration than the other two; two are big thick O-rings and two have a much smaller cross section diameter, I read on this forum that can be typical? One thing I did noticed was the bores in the sump for the O-rings, while they are all smooth, they are not straight (if that makes sense). When I run my finger through the bore I can feel some waviness in the bore. my thought is maybe with the thermal expansion the intake runner moves to a position where the O-ring no longer creates a good seal and after the engine cools off it seals again? Any thoughts on where else there might be an induction leak or any thoughts on possible other culprits? Thanks! Scott With the two side cowls removed, connect the blow side of your shop vacuum to the open ram air door in the front of the cowl, seal with some duct tape. Spray the intake pipe with soapy water, pay attention to leaks at the intake tube flange gaskets and the O rings. There are two different sizes of O rings for intake pipes, I’ve never heard of both sizes on the same engine.
M20E for me Posted October 17, 2022 Author Report Posted October 17, 2022 Yes, I bought it in Oklahoma and flew it out to San Diego with a few stops along the way. Didn't have a problem until landing in San Diego. Nothing was done to the engine/plane between Oklahoma and San Diego. The rough running went away for a flight or two then came back. The A&P initially adjusted the mixture (enrichened it) but the problem came back. He has been pretty sure all along that it is an induction leak but cant seem to isolate where the leak is coming from, hence the replacement of the intake runner O-rings and gaskets. He has talked with a Lycoming engine expert who also isn't sure of what the source could be. After reading Riche's post I'm thinking he might have richened the mixture too much? Something to try,
M20E for me Posted October 17, 2022 Author Report Posted October 17, 2022 13 minutes ago, M20Doc said: With the two side cowls removed, connect the blow side of your shop vacuum to the open ram air door in the front of the cowl, seal with some duct tape. Spray the intake pipe with soapy water, pay attention to leaks at the intake tube flange gaskets and the O rings. There are two different sizes of O rings for intake pipes, I’ve never heard of both sizes on the same engine. I'll give that a try. With it only acting up when warm I'll have to get the set up ready and do it after the engine has warmed up. I was surprised to see there were to different styles of runners on the same engine too!
Guest Posted October 17, 2022 Report Posted October 17, 2022 Just now, M20E for me said: I'll give that a try. With it only acting up when warm I'll have to get the set up ready and do it after the engine has warmed up. I was surprised to see there were to different styles of runners on the same engine too! Did you check the sniffle valve on the bottom of the engine? It’s right above the muffler, it’s a plastic ball inside the blue AN elbow fitting. They are known to leak.
M20E for me Posted October 17, 2022 Author Report Posted October 17, 2022 9 minutes ago, M20Doc said: Did you check the sniffle valve on the bottom of the engine? It’s right above the muffler, it’s a plastic ball inside the blue AN elbow fitting. They are known to leak. Yes, we removed it and it was clean, almost new. The ball moves freely and no gunk inside.
carusoam Posted October 18, 2022 Report Posted October 18, 2022 Let me guess… No FF instrument? It really helps to know what FF you have for leaning on the ground… It also is important for troubleshooting… Best regards, -a-
M20E for me Posted October 18, 2022 Author Report Posted October 18, 2022 8 hours ago, carusoam said: Let me guess… No FF instrument? It really helps to know what FF you have for leaning on the ground… It also is important for troubleshooting… Best regards, -a- No, not yet, going to get a JPI 730 with FF. 1
81X Posted October 18, 2022 Report Posted October 18, 2022 Take a look at your logbooks as well. If it’s been over 10 calendar years since the fuel system has been overhauled, consider it time. There are a lot of rubber components and o rings that should be replaced periodically. I had similar symptoms where my 231 wouldn’t low idle when warm and I needed about 1000 RPM to keep it going. I thought it just needed adjustment until it quit on a takeoff roll.
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