Engine hesitation ~1500 Piper Archer II

cowman

cowman

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Had this happen a couple of times now, first time I would have believed it was a fluke, few more times isn't a fluke...

The scenario is this: I've just turned final and at some point decide I'm just a touch lower than I'd like. Throttle is maybe 1300-1500rpm. I bump the throttle up slightly to add 100rpm or so and the engine stutters/hesitates. This lasts only a moment, I don't even think a full second before it recovers and is running fine with my extra 100rpm bumped in.

I've had nothing unusual taxiing, on my runups, takeoff, climbout, or in cruise flight. Only this split second hiccup that had no operational consequence in this one specific set of circumstances... but it has repeated it's self.

I think I need to have an A&P check it out but first I thought I'd consult the hive mind to see if I can give him something more specific to focus on. I did just put in a new left mag back in Jan and don't have a lot of hours on it since then... my instincts say this is a carb thing though.
 
Are you 100% sure you're full rich?
 
I'm 100% sure the mixture controls are set to full rich.
 
I get the same thing. Pretty sure it's a low jet high jet transition on the carb.

Mine does it every time I go full throttle on takeoff, doesn't matter if I'm full rich, not quite FR, or leaned for best power.
 
cowman said:
Had this happen a couple of times now, first time I would have believed it was a fluke, few more times isn't a fluke...

The scenario is this: I've just turned final and at some point decide I'm just a touch lower than I'd like. Throttle is maybe 1300-1500rpm. I bump the throttle up slightly to add 100rpm or so and the engine stutters/hesitates. This lasts only a moment, I don't even think a full second before it recovers and is running fine with my extra 100rpm bumped in.

I've had nothing unusual taxiing, on my runups, takeoff, climbout, or in cruise flight. Only this split second hiccup that had no operational consequence in this one specific set of circumstances... but it has repeated it's self.

I think I need to have an A&P check it out but first I thought I'd consult the hive mind to see if I can give him something more specific to focus on. I did just put in a new left mag back in Jan and don't have a lot of hours on it since then... my instincts say this is a carb thing though.
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My Cherokee 180 always did this if I aggressively added power. I learned that slowly increasing RPM fixed it.
 
Accel pump too weak?

Btw, instead of "mixture full rich", you should be checking "mixture set". Especially now in the summer where DA even on the ground is higher than normal.
 
cowman said:
Had this happen a couple of times now, first time I would have believed it was a fluke, few more times isn't a fluke...

The scenario is this: I've just turned final and at some point decide I'm just a touch lower than I'd like. Throttle is maybe 1300-1500rpm. I bump the throttle up slightly to add 100rpm or so and the engine stutters/hesitates. This lasts only a moment, I don't even think a full second before it recovers and is running fine with my extra 100rpm bumped in.

I've had nothing unusual taxiing, on my runups, takeoff, climbout, or in cruise flight. Only this split second hiccup that had no operational consequence in this one specific set of circumstances... but it has repeated it's self.

I think I need to have an A&P check it out but first I thought I'd consult the hive mind to see if I can give him something more specific to focus on. I did just put in a new left mag back in Jan and don't have a lot of hours on it since then... my instincts say this is a carb thing though.
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I get the same thing on the Archer I rent. Once I reduce power to 1500rpm abeam the numbers, any slight increase in power is accompanied by a momentary hesitation. Quite un-nerving the first couple of times it happens.
 
cowman said:
I'm 100% sure the mixture controls are set to full rich.
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It's hard to tell without hearing the hesitation, both excessively lean and rich can cause the same thing, but they sound different. First place I would go is the air filter, next place is the accelerator pump.
 
Hmm so this is "normal"? I've flown this thing for over 2 years now and this is the first I've noticed it.
 
cowman said:
Hmm so this is "normal"? I've flown this thing for over 2 years now and this is the first I've noticed it.
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On my old Cherokee it depended on how fast I pushed the throttle.
 
I have this happen quite often on my Archer II. I've found it happens less when the mixture is just a bit leaner than full rich.
 
cowman said:
Hmm so this is "normal"? I've flown this thing for over 2 years now and this is the first I've noticed it.
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No, it's not 'normal' for the plane, it's 'normal' for people to not care that the plane isn't right as long as it runs and flies. There is something 'not right'. In Australia if you would complain you would be told, "She be right mate.":lol:
 
I say accelerator pump issue... Spray some nitrous in it, that will get rid of the hesitation. Ha Ha
 
Mine does it as well(Cherokee 180, 0-360-a4a). When I go up through 1300-1500 it hesitates and then smooth's out. Going back down is fine. I've also noticed that in the cold winter it doesn't happen but in the summer every time(maybe I need to richen it up some for the summer). I've been told its the transition from the idle circuit to the main circuit. Going slow or fast through it doesn't change anything in mine.

Last person on here who had that wanted it fixed and he got a new carb. He said that did it, or was that on another forum?? At any rate, normal or not, a few people do complain about that.
 
Perfectly normal, henning.
 
It's inherent to the engine, as it is with many small, carborated engines. Throttle response is not going to be instant. Its a simple problem of instant increased air flow with no additional fuel to burn until the carb can create the vacuum drawing in the go juice. Simple physics. Fuel will flow but it has to work its way through the circuit and that will take milliseconds to make it to the combustion chamber. At higher RPM, the delay is reduced to a time slow low its unnoticeable.
 
How many of the owners that are having these problems are running Kelly overhauled carbs?
 
This is typical. If it has a 10-3878 carburetor you can fix it by having it upgraded to the 10-3878M or the next higher applicable 10-number which I can recall. Charlie Melot Zephyr Engines
 
charlie said:
This is typical. If it has a 10-3878 carburetor you can fix it by having it upgraded to the 10-3878M or the next higher applicable 10-number which I can recall. Charlie Melot Zephyr Engines
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^^^^^^And you can take that to the bank!
 
Happened in all the multiple warriors I flew. Something about changing power, makes you sit up and take notice, but by the time you do there is nothing to notice.

I asked the a&p about it, but he wasn't concerned about a momentary hesitation unless I called is a sputter and that isn't the right description. Also, the engines keep running and those airplanes flew 500+ hours/year for over a decade and there has never been an engine failure...a few pilot failures, but never the engine.
 
cowman said:
I'm 100% sure the mixture controls are set to full rich.
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Try leaving the mixture to running lean position. The only time you should be full rich is on take off or go around. Don't try this on final, but go up and try it at 2,500 AGL just to be sure and then try it in the pattern. I never land full rich in a fixed wing. :no:

Also, like Henning said the accelerator pump may be weak, but try running lean in the pattern and see if that makes a difference.

On a side note, this is why patterns should be tight to the runway. If the big fan quits you can glide to it.
 
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Tom-D said:
Apparently you are up to date on the problems of the kelly overhauled carbs.
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If you have a bad carb, what makes it ok much less "right"?:dunno: The plane in the OP just started having this problem. You may be ok with this stuff and accept broken junk on your plane because it still flies with it, but that does not make it normal or right.
 
Henning said:
If you have a bad carb, what makes it ok much less "right"?:dunno: The plane in the OP just started having this problem. You may be ok with this stuff and accept broken junk on your plane because it still flies with it, but that does not make it normal or right.
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That's true, but I do not except a unairworthy aircraft so don't insinuate that I do. and your beliefs that the accelerator pump causes the fuel air ratio to go lean is not correct. with the Kelly overhauls they go too rich.
 
Has any one really read the OP's post? his engine stumbles when he make small throttle adjustments.
 
Tom-D said:
That's true, but I do not except a unairworthy aircraft so don't insinuate that I do. and your beliefs that the accelerator pump causes the fuel air ratio to go lean is not correct. with the Kelly overhauls they go too rich.
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I wasn't directing that comment at you, rather to those who claim it's fine. As for rich or lean, that's why I said before one has to hear the problem to understand the problem. The reasoning given before by others would be solved with the accelerator pump. If the engine stumbles, there is a problem of one form or another.
 
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I get this on my Archer when I gas it for take off, or if I need to bump up the throttle a little while on approach. I chalk it off to the heat and humidity here in Florida. It's never cause me a bit of worry, though.
 
stevenhmiller said:
I get this on my Archer when I gas it for take off, or if I need to bump up the throttle a little while on approach. I chalk it off to the heat and humidity here in Florida. It's never cause me a bit of worry, though.
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You have a problem that you just accept due to ignorance of it being a problem.
 
Q - To the OP - Does it still hesitate if carb heat is ON thru the throttle change? This might suggest if it is experiencing a temporary lean or rich mixture. Carb heat will normally richen a steady state mixture in a calibrated carburator.

Another cross check - is it worse or better on cooler/dry days?
 
Henning said:
I wasn't directing that comment at you, rather to those who claim it's fine.
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I get the feeling you don't understand what the OP was describing. It is a minor anomaly that is common to many Pipers. To characterize it as "broken" or "junk" is inaccurate and shows that you're talking about something you don't know about.

I describe it best as a "skip", like a plug didn't fire, once. Not sure why it happens, maybe something like baffling design in the -28 combined with slower air flow making a certain cylinder hotter under climb or approach conditions, which combines with a particular engine RPM and throttle change to produce a momentary skip. That's as good a guess as any as to the cause.

Working off memory, which is dangerous, but I recall it happening more often in the summer.

I do recall the first time it happened was on crosswind and I was ready to immediately turn back to the airport, except that the engine was still running. So I stayed in the pattern and landed, did a runup and tried again - it happened at pretty much the same point and the engine kept running. It's almost predictable and doesnt' happen anywhere away from the airport or in cruise. *shrug*
 
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Minor anomaly = ain't right. Don't want to fix it? Fine, doesn't make it right.
 
Henning said:
Minor anomaly = ain't right. Don't want to fix it? Fine, doesn't make it right.
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It isn't right. But it also can't be nailed down as to why it happens AND it's such a minor thing that it doesn't have an impact on the flight. I would compare it to getting a squeak from your sun visor when you turn it. It ain't right. But you're not going to ground the airplane because of it.

It does not rise to the level of "broken junk". You're back pedaling now because you were too extreme earlier.
 
bflynn said:
It isn't right. But it also can't be nailed down as to why it happens AND it's such a minor thing that it doesn't have an impact on the flight. I would compare it to getting a squeak from your sun visor when you turn it. It ain't right. But you're not going to ground the airplane because of it.

It does not rise to the level of "broken junk". You're back pedaling now because you were too extreme earlier.
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The carb is defective, replace it with the one Charlie listed. It's broken junk, it just still manages to work... kinda.

I'm not back pedaling a bit, I say fix it correctly.
 
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I've only flown a few Pipers and I only noticed this anomaly as it is described on one. I have been told though that it is fairly common on them so maybe not an issue but the post below by the OP has me wondering if it is something new or if it has just gone unnoticed until now. I somehow doubt the latter. In my opinion, an anomaly common to type should be more or less omnipresent and not just pop up all of a sudden with a new consistency. It is worth checking out.

cowman said:
Hmm so this is "normal"? I've flown this thing for over 2 years now and this is the first I've noticed it.
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Tom-D said:
And that is which way?

even the carb swap doesn't fix it some times.
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Then find the induction leak or whatever else is the root of the problem. This is not a "normal" way for an engine to react, plain and simple; it's indicative of a problem. Do you drive your car around when it hesitates every time you step on the gas?:dunno:
 
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