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Auto Mechanics 1A. Your idle jet or the carb passage leading to it is plugged. Carbs have a separate idle circuit because the high-speed circuit is too big to let the fuel atomize properly with low air flows. Greg At 03:19 PM 6/5/03 -0300, John Stevens wrote: >----[Please read http://ercoupers.com/disclaimer.htm before following any >advice in this forum.]---- > > >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/ > > ========================================================================== ==== 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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