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I have been having an issue with my coupe at idle - she runs fine at 900 rpm or better but seems to want to stall below this mark unless I put the carb heat on. I have a C75-12F with a stromberg carb in mine - the engine has just been "0" timed and have only put about 6 hours on her thusfar. What I have found is that the RPM decreases with carb heat during run-up (1500+ rpm) which is what I expect, the mags have 0 differential between them during run-up but when I pull back the throttle to idle the engine starts to sputter and stall unless I pull the carb heat out. At this point she seems to idle well around 800 or so rpm. The other solution is that I keep the RPM up around 900-1000 without carb heat. This isn't a problem during cruise descent since I use carb heat and leave the power setting up a bit anyway, I haven't tried pulling her all the way back without carb heat in flight and am not in a hurry to find out. Otherwise she starts pretty easily, and runs great at cruise power (2000-2200 RPM). My AME (A&P) has messed a bit with the main mixture setting with varying results (but no solution), he seems to think that it's a sparkplug fouling issue (I'm running M100 mineral at the moment) but I'm not convinced. Although the lower plugs may be fouling, the uppers should still be clean and able to deal with the air/fuel mixture for the short period that I have her in idle. Has anyone had this issue before or has any suggestions for alleviating this issue? My feelings is that the effect of the carb heat is having the effect of letting the engine breathe better and that my air filter may be clogged up and in need of cleaning / replacing. I am just throwing out the question in case somebody else has seen the issue and has some experience with this problem. Any suggestions would be appreciated. John Stevens 415-C owner going through withdrawl at the moment.... ========================================================================== ==== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/
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