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AFP throttle shaft air leak

AN23

Well Known Member
IO-360 with AFP fuel injection and one emag and one pmag . Idle has gotten progressively worse. Manifold press historically varied between 9-12 inches at idle with corresponding rpm change of 100-200 rpm. Checked for leak in manifold press and MAP sensor line by capping at engine. No change. Absolutely no evidence of any leaks either at cylinder or rubber connectors. Talked to Don and we played with idle mixture and it seemed better for a while. We chalked it up to hot fuel, light prop and perhaps God’s will. Yesterday, I noticed on runup that BOTH mags had a larger drop than usual but still well within limits. Takeoff indications were all normal but decided to stay in pattern. Upon reducing power, noticed a slight roughness that I hadn’t noticed before. Engine got rougher as power was reduced for landing. Taxiing in, the idle was just terrible below about 1100 rpm. Today pulled off cowl and checked compressions (excellent), plugs and leads (all good) and visually checked the induction system for signs of leakage (none). Decided to pressurize the induction system with output side of small vacuum and no leaks found until I came to the throttle plate shaft (where throttle cable attaches). It is leaking to the point that it will blow the soapy water off as fast as you can spray it on. I have a call into Don now but don’t expect to hear from him until Monday. Checked for other threads on this but with no luck anyone else have this experience? Can’t be right as it is obviously sucking unfiltered air in at this point.
 
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Just for everyone?s info, after talking to Don, this throttle plate shaft leakage is completely normal. He suggested I go back and check the plugs and leads again but also cautioned that this time of year (really, really hot), he gets lots of calls with idle issues due to fuel boiling in the lines.. So, I started back at the plugs again. I had just read about people having issues with plugs with the removeable ferrules so I checked mine and found six of the eight loose!!!!!! Needless to say, those were trashed and new, non-removeable ferrule plugs were installed. All good.
 
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