63 Cessna 182F 0470R #5 not firing at idle

[fivezero]

Since I owned the plane (7 years now) I have been seeing the number 5 cylinder show low egt at idle. When the plane is taken up to 1700 rpm the cylinder EGT comes alive. It is more pronounced when the engine is cold. When warm it only happens at idles. When it is cold sometimes the rpm where the cylinder comes alive is higher and sometimes requires me to do a 2000 rpm run up to get the number 5 to make EGT. When in the green arc it never stumbles and I never notice it after flying. I have checked for induction leaks and the plugs have been checked good. I lean aggressively on the ground as I thought it might be flooding out. The compressions are low but acceptable for the continental.

Anyone else have this problem? Any thought or ideas on possible causes? Any input is appreciated. The engine is way over TBO but the oil analysis is good and this is the only problem the engine has.

Thanks
Chuck

 

[Tom-D]

The compressions are low but acceptable for the continental.

Apparently not..

 

[Skip Miller]

I’m guessing you have low compression in cylinder 5. Someone will be along shortly to tell you a quick method of determining if you have a burned exhaust valve or a problem with your piston rings/cylinder.

Do you know the results of a compression test done at annual inspection time? I am betting it will show a steady decline over the years...

-Skip

 

[fivezero]

#1 60/80 #2 74/80 #3 65/80 #4 60/80 #5 64/80 #6 70/80 from last annual in June of 2018.

#5 History
2013 60/80
2014 68/80
2015 71/80
2016 70/80
2018 64/80

 

[timwinters]

Mine does the same thing. I won't say "it's not firing" rather #5 runs richer than the others. It's obvious when the plugs are pulled...#5 plugs definitely indicate a rich run. It also runs 100*F cooler in cruise than the others. I've f***ed with it numerous times (sealing up the intake system, etc) but nothing thus far had made a difference. It's done this since the last OH. My compressions are great for a continental, all were over 70 last month at annual and all have been over 70 since the OH which was 3 years and 300 hours ago.

How do your plugs look? (never mind, I reread your post and see you said the plugs look good...I guess I'd ask what "looks good" means.)

You may not have a problem other than it running rich. And #5 is a weird cylinder to be running rich...considering how far away from the carb it is with the F***ed up O-470 induction system.

 

[Tom-D]

2018 64/80

Tell us where the air is going ... exhaust valve? Crank case? Intake valve?

Are we certain this is a compression problem.. Has anyone checked the spark quality?

Have you ever done an idle mag check?

Try this tell us why happens.
Run the engine at IDLE 500-650 RPM is #5 firing? do a mag check L Both R Both, did anything change between mags?

 

[timwinters]

Are we certain this is a compression problem..

You and Skip were the only ones who went there in the first place. And you certainly seemed sure then.

 

[Tom-D]

You and Skip were the only ones who went there in the first place. And you certainly seemed sure then.

AND after that he told us it had 64.
So are we sure it's a compression problem?

 

[bnt83]

Since I owned the plane (7 years now) I have been seeing the number 5 cylinder show low egt at idle. When the plane is taken up to 1700 rpm the cylinder EGT comes alive. It is more pronounced when the engine is cold. When warm it only happens at idles. When it is cold sometimes the rpm where the cylinder comes alive is higher and sometimes requires me to do a 2000 rpm run up to get the number 5 to make EGT.

Thanks
Chuck

Mine does the same thing.

​

We have an O-470R in a 68 182 and it does pretty much the same bloody thing on #5. It runs fantastic after it gets warmed up. This was a factory reman about 700 hours ago. Compressions are about what you guys are seeing.

Only really noticed if after installing a full engine monitor.

I've noticed when starting it from dead cold, it really helps to pull the carb heat on and let the carb temp get up to about 100F simultaneously leaning like crazy, it starts running better much quicker than just letting it suck 40F air into a cold induction system.

 

[timwinters]

​

We have an O-470R in a 68 182 and it does pretty much the same bloody thing on #5.

I'd bet you have a compression problem!

 

[bnt83]

Mine does the same thing.

I'd bet you have a compression problem!

I think the carburetor and induction system is just too sloppy to get the performance we think it should have.

Pulls hard, runs smooth, good mag drops and still show these symptoms when cold at low RPM, always on #5. Always #5 cooler in cruise

 

[timwinters]

Sarcasm...

The O-470 induction system indeed SUCKS!

 

[fivezero]

Thanks for the replies. This has done it ever since I have had the plane. The problem felt like the 5 was too rich and getting flooded out when cold. I had heard about the problem with the induction system but could not remember if everyone had a problem with 5 or if it was another cylinder. I have never had a problem with it but I let the engine get nice and hot before I get going. What brought this to a head is I let someone borrow the plane and he stalled it on taxi and before the stall he had the rpm hunting with approx. a 100 rpm up and down. I thought he had not let it get warm or had not leaned it enough or too much. It sounded like the rpm problem was 5 coming in and going out. An unrelated starter problem ended his day. I later talked to folks and they said he just started it then started taxi without getting it hot or even warm and I think that is what caused the problem. I have to get the starter fixed then I want to run the engine myself to see if it is the usually 5 problem or if it is something new. Again, it has been checked out before and never can find the problem so I wrote it off as a quirky problem that I just had to live with.

I appreciate my fellow 0-470 owners as if we all have a problem with 5 then I may not have a problem.

 

[jesse]

If the problem didn’t exist before and just started, then I would pursue fixing it. All airplanes are a bit different. Thing is..you didn’t have this before...so I wouldn’t accept it now.

Personally, I’d thoroughly check everything that makes that cylinder bang: compression, spark, timing, and fuel. One of those things isn’t working like it used to on that cylinder.

Something changed. Find it. Everytime I’ve accepted a problem that started because someone told me it’s normal, I’ve come to regret it.

 

[Tom-D]

It is a 0-470, convert it to a 0-520, for a Mear 100,000 you can make this problem go away..

 

[benyflyguy]

I later talked to folks and they said he just started it then started taxi without getting it hot or even warm and I think that is what caused the problem.

Sounds like a friend who isn’t getting handed the keys anymore. Kinda crappy that he turned the key and burned.

 

[timwinters]

If the problem didn’t exist before and just started, then I would pursue fixing it. All airplanes are a bit different. Thing is..you didn’t have this before...so I wouldn’t accept it now.

I think you misread, Jesse...

Thanks for the replies. This has done it ever since I have had the plane.

 

[wilkersk]

Well, now I'm confused. You say the engine runs fine, doesn't stumble. Compressions are within limits. And, I've always been under the impression that EGTs at idle weren't really something to put a whole lot of stock in. If everything else is OK, is this really a problem?

 

[sardonux]

I have a ‘63 182F with a higher-time (1430 hrs) O-470-R and see exactly the same performance.

Recently I moved to a hangar with power and now have the luxury of an engine heater for the winter, so the cold weather side of the equation has been minimized.

I’ve not found any arguments in my research that this is an issue that needs to be addressed. I like knowing (thanks to my EDM 730) this information and use it to ensure I’ve got the entire engine warmed up before going to takeoff power. When I was tied down outside and temps were 15 degrees F, it definitely took a while to get up to operating temps I desired.

 

[timwinters]

It definitely sounds like an issue common to O-470s and their #5 cylinder. One other thing worth checking though, if you haven't.

Have you checked to ensure that all your EGT probes are mounted the exact same distance down the stack from your cylinders? If not, actual temps are irrelevant.

I *believe* EI suggests 1" as optimal. Whatever it is, I was able to mount mine at that location.

 

[wilkersk]

This doesn't say anything about "low" EGT. But, its one of my favorite Mike Busch articles.

http://www.gami.com/articles/egt_myths.pdf

 

[fivezero]

I have my routine with the plane and I think the person that borrowed it just didn't understand the engine. He is used to flying injected engines so I think the carb threw him for a loop. I was a car mechanic at one point in my life and the problem really seemed to act like a cylinder that was flooding out and not firing. 5 always runs cooler and that confirms it is getting more fuel than the rest. The fact that it would clear up with after warm up or with higher RPM leads to the conclusion that the non firing plug was clearing out.

 

[timwinters]

Mentioning Mike Busch, or worse, linking one of his articles, in any technical thread on an aviation board should be the aviation equivalent of Godwinning that thread.

 

[3393RP]

↑

I later talked to folks and they said he just started it then started taxi without getting it hot or even warm and I think that is what caused the problem.

Sounds like a friend who isn’t getting handed the keys anymore. Kinda crappy that he turned the key and burned.

I wouldn't attach any blame based on what "folks" said. That's not fair to the friend. Besides, how could it have "caused the problem" when symptoms have been occuring since the OP purchased the aircraft seven years ago?

 

[benyflyguy]

↑





I wouldn't attach any blame based on what "folks" said. That's not fair to the friend. Besides, how could it have "caused the problem" when symptoms have been occuring since the OP purchased the aircraft seven years ago?

Not attaching blame. Agree the problem predates that. But it’s a crappy thing to do to an airplane right??

 

[Duster]

When oat is below freezing or near, it is pretty common for 5&6 to flood at idle, even if the engine is pre-heated and leaned for ground ops. They will fire up normally and run smooth for the first minute or so, then the front cylinders will potentially start flooding as mentioned; to the point that if you try to shut down with the mixture, the engine will continue to run.

The solution is to run carb heat during warm-up and lean properly, or you can insulate the crossover tube, which has helped resolve that issue on my 0-470.

If that is not what is causing the problem, I would suspect an induction leak (they can be a real challenge to pinpoint sometimes), or it could be a cam/valve issue. Do one thing at a time, and hopefully it is an easy fix.


Sent from my iPhone using Tapatalk

 

[Witmo]

I don't think taxiing is going to do much of anything to an engine right after engine start unless you use takeoff power to roll over the chocks.

 

[SloRoam]

I have been chasing a similar issue for some time. Using soapy water and a vacuum to pressurize the system, I found several induction leaks.

To rule out induction leaks, try writing down the egts and chts at wot and then at say 15", and see if the differences between cylinders are the same or different in both states.

If the differences are the same under atmospheric pressure (wot) and some vacuum (15") you probably don't have an induction leak.

Also: when the engine is warmed up fully, does it fire at idle?

What's your mp at idle btw?

 

[jesse]

Taxing an airplane immediately after starting it doesn’t hurt a damn thing and won’t cause an issue. You’re sitting there holding the brakes stopping the movement. There is no reason to wait for it to warm up before you allow the airplane to roll forward. The engine doesn’t know or care about the brakes.

Would I take off immediately after starting a cold engine? No. But by the time I get to the runway threshold and am ready to go, so will the engine.

 

[SloRoam]

If it helps, here are my idle temps - keep in mind this is a o-470-50 (pponk), for what its worth. And yes, my #5 is also the hottest. Typically #5 at idle is hottest for EGT, and #2 for CHTs. This is about 1 minute after startup.

 

[bnt83]

I'm pretty sure our 182 has been doing this since before we bought it, well this year I decided to look into it suspecting sticky valves Dad & I did the "rope trick", ei pulled the valve covers, rocker arms, valve springs and dropped the valves into the cylinder for inspection. The first sign that there was no smoking gun is that both intake and exhaust valves traveled freely in the guides with no binding at all. The bores of the valve guides were clean, the appropriate sized reamers didn't do anything but confirm the ID was correct. The valve stems were also fine.

Additional troubleshooting included taking a video of starting the airplane from room temp and watching the engine monitor, 2 strokes of the primer and it fires quickly, during initial start #5 fires for 45 seconds with the EGT coming up similar to all others then for whatever reason at a lower RPM it starts missing. It acts the same on all magneto switch settings. I swapped the spark plugs from #3 to #5 and vice versa, absolutely no change. Its not mags, its not plugs, its not the wires, its not the valves. Compression test was 70 over 80 with all the leakage noise indicating normal ring leakage. Both top and bottom spark plugs are bone dry as they should be.

Its cold out this time of year and it seemed like I could improve the situation by pulling full carb heat and aggressively leaning (and regulating/reducing carb heat as the muffler warms up) and it seemed like #5 would start running better, as the engine warms up a normal mag check at 1700 its smooth and firing on all 6.

Another forum post suggest taking all the intake runners off, bolting them back on in-place without the hoses and clamps and the balance tube on the front and seeing how well aligned they are, and re-positioning them to get the best alignment possible.

(Engine history, its basically 800 hours from factory zero -timed, the TCM mags are 477 since 500 inspection, spark plugs have about 177 hours on them.)

 

[SloRoam]

Revisiting this thread I'm very glad to hear of others experience about flooding cylinders five and six. I just spent some quality time working on my plane and annual, and was able to remove the carb, use a blanking plate to block the intake, and pressurize the intake system, and found a few very large intake leaks that I had not found with the soapy water and vacuum method.

I also found after all of that maintenance and ensuring that I had no induction leaks, the number five on take off, would run a lot cooler EGTs, even after I insulated the crossover tube.

If I use partial carb heat, it goes right back into line, at cruise my number five is in line with all the others, and it idle, when it's cold, I found that if I simply fire it up to about 1100 or 1200 RPM and then lean aggressively, it stays roughly in line with the others.

I also bore scoped the valves, and my compression is also the same in five as it is in all the others, so I'm in agreement with numbers five and six potentially flooding when it's very cold.

I've also come to the conclusion that the heat shields force most of the clamps too far apart on the induction tubes, and that after looking at a few other 182's on the airfield almost all of them have bent induction tubes from over torquing.

I would love to see an aftermarket, or improved induction system?

 

[bnt83]

I wonder how it would act if a guy drilled a tiny hole say like a #50 drill bit, into the plugs of the fuel injection ports on #5 and #6.

 

[thomasdr72]

If it makes anyone feel better to have another data point, our bird has an IO-470S with stock injectors (no GAMI yet) and it pretty much does the same thing when cold and/or idling. Compressions are perfect, plugs are great, mags almost new, engine is about 450 SMOH. I had some unevenness with in-Flight temps until I went on a campaign to reseal all the baffles to the engine, and check the cowl for fit. Now temps across the board in flight are consistent for a non-GAMI engine. I have chocked it up to type design as well...