I am relatively new owner of 1971 PA28-180. If I reduce throttle to control taxi speed, the engine seems to run very rough ( approx 400-500 rpm.) It runs smooth at 900 and above. But at 900 above rpm, I have to use excessive breaks to control the speed. So I am almost taxing at 900-1000 rpm with both feet on breaks. What am I doing wrong? I lean the mixture after start. last three run-ups I had to burn the left mag as it was dropping 190 rpm when switched to left mag alone. That could be separate issue altogether. I just had first annual done , engine compressions were really good per AP. Any advice will be appreciated.
Either condition You have (Slow idle speed, excessive RPM drop) will cause roughness but with both conditions combined it's a given. It would be nice if these engines would idle smoothly at 400-500 RPM but they just won't. I have a 6 cylinder and it doesn't idle acceptably smooth until 600-650 so I imagine a 4 cyl is higher yet, but You'd never get it on the ground if You idle much higher.
Don't know if this is significant but I don't have this problem in 160HP Warriors or 180HP Archer IIs. Could it be because they're club rentals and get the balls flown off of them? Maybe.
JimC Wrote:
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> A 190 rpm mag drop is unacceptable. You need to
> find out what is causing that immediately.
> Sometimes it is just improper timing on that mag.
>
> 400 to 500 rpm is way slow. The engine should be
> expected to run rough at that speed.
> JimC
Jim,
How do you control taxi speed. At 900 rpm, the taxi speed is too high.
I read somewhere taxi should be done at idle and breaks used the minimum. I am literally holding breaks hard to reduce speed which is not good for the break pads either.
Hi, I have a 180 as well. You should ask your mechanic to check your idle mixture and idle speed setting. Idle speed should be about 650 RPM with throttle full back and the mixture adjusted to give a small (10-50) RPM rise at idle speed just before engine shuts down if you lean very slowly to idle cut off. An excessively rich idle mixture could be causing your roughness and fouling your plugs and causing the rough mag check.
If the idle mixure is set properly, I do not believe you should have to lean at idle unless you are at a very high elevation.
One last thought, the speed at which the airplane rolls along at idle can also be affected by your tire inflation! If you have over inflated your tires to the point where they look perfectly round, you can expect to roll along quite fast compared to the normal inflation profile. Check your owners handbook for proper inflation pressure.
Jim C... You must have to bring your engine to idle considering your " aft facing powerflow" gives you 3 knots of extra speed. LOL LOL LOL!!!! LOL!!!! Biggest CROCK I ever heard!!!!
