Piper Seminole: Rough Engine at Full Power

oktex88

oktex88

Well-Known Member
I was out flying a Piper Seminole today that had just got out of maintence.. was cold soaked and she wouldn't start so had to get a preheat to start her up.

Anyway, I got her up to cruise and leaned out the engines... the left engine leaned out fine however the right one seemed to lean out (EGT peak) with a way cooler EGT than the left. I also had trouble keeping the Manifold Pressure even with the left engine with about an inch difference in throttle settings which seems to be a lot more than the other seminoles in our fleet I"ve flown.

After some manuevers and getting setup for a GPS approach I bumped up both throttles to full power to there a little quicker and the right engine started to vibrate a lot, kind of like when you lean the mixture out too much. (Mixtures were rich at this time) All engine insturments checked normally and the only way to get the vibration to stop was to retard the throttle a little. I noticed that that the airplane had been written up yesterday for the same issue and maintence replaced the #4 cylinder...Any ideas as to what might actually be going on here?
 
What EGT instrumentation do you have/are you using? Any other engine monitoring equipment? How was the run-up? What were the fuel flows/mp/RPM settings?

-mini
 
minitour said:
What EGT instrumentation do you have/are you using? Any other engine monitoring equipment? How was the run-up? What were the fuel flows/mp/RPM settings?

-mini
Click to expand...

EGT, Oil Press, Oil Temp, Fuel Press All normal. CHT was on the cold side even with the cowl flaps closed but within normal operating range albiet barley. Run up was normal, no problems with any of the mags. When the right engine was vibrating MP was around 20in RPMs 2500. Altitude was about 6,000ft. Closer to the ground i.e. the two takeoffs I did I didn't notice any vibrations.. nor on the climb out. Also tried leaning the mixtures on the right engine and it had no effect on the vibrations. Seems to me it is just happening at the higher altitudes. Maintence also did a ground run up an hour or two before I flew it with no problems.
 
Did you try carb heat? Could be carb icing or induction icing, could also be carbon tracking in the magnetos, down low that wouldn't cause a problem but up higher where there's less resistance in the air it shows itself. Were fuel pressures and flows normal?
 
I had suggested trying the carbheat but the person I was flying with didn't seem to think that was the problem, he was PIC. Don't think it was carb ice due to the fact that this was a disrepancy reported the day before as well and roughness was strictly only at full power.
 
oktex88 said:
I had suggested trying the carbheat but the person I was flying with didn't seem to think that was the problem, he was PIC. Don't think it was carb ice due to the fact that this was a disrepancy reported the day before as well and roughness was strictly only at full power.
Click to expand...

so you guys didnt even try the carb heat? hmm. i have about 1000 hours in the PA-44 and never once had carb ice. But I never flew anywhere that required pre heating the engine either! Did you replicate the problem on the ground?
 
Carb Heat was one of the first things in my mind to try and I suggested it. This was my first time getting a preheat and boy my preflight was COLD! Didn't try to run it up on the ground again, just reported the discrepancy to dispatch, I'm paying for the time so I'd rather let maintenance do it on their dime. I guess I will try to get ahold of the aircraft book again and see what maintenance said. My Instructor and I just couldn't think of anything specifically that could cause this to happen only at full throttle up at altitude. Didn't even have any hiccups at all during the run up.
 
Looks like you fly at UND, me too. I flew the semi back in december when it was very cold. I remember having the same problem. All i did was lean the mixture. you said you had it rich, that could have been your problem. I leaned my right engine and it ran smooth, just as smooth as the ice is on all ramps :rotfl:
 
which tail number? 581 just had a carb replaced, the plane you flew might have the same problem
 
an intake gasket was just replaced a few days ago. I flew it last night and it was perfect

they also cleaned the plugs a few days after the gasket
 
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