Coming back from Savanah GA today just leveling at 9500' I experienced a power loss and rough running on the IO-320 in my RV9A. Looking quickly at the engine monitor I could see the EGT on #1 headed to zero. All other EGTs good. After doing some troubleshooting I discovered that richening the mixture substantially cause the engine power to come back and #1 EGT coming back up but it kept going when reaching the other EGTs it kept going and went above 1500, 300 degrees above the other three. Full rich brought the EGT back to about 1450 and engine running OK, but other EGTs much lower by about 300 degrees. I started heading for a nearby airport and dropping altitude. About 3500' #! EGT started coming down suddenly and engine running very well. EGTs now all equal. All good, CHT and EGT exactly where they should be. I releaned the engine and all remained good. I decided to climb and keep an airport in gliding range and continued the trip home about 45 minutes. Engine continued to run properly. My conclusion is that a something was blocking either the injector or flow divider to #1 and then either passed or dissolved
What do you think?
Ed.
PS, Edit, forgot to mention I had leaned to about 20 degrees LOP at 9500, which is normal for me and never an issue prevously. Rolling back the mixture to well ROP did NOT bring the #1 EGT back up from zero nor did the engine roughness change until the mixture was richened almost back to full rich at 9500.
What do you think?
Ed.
PS, Edit, forgot to mention I had leaned to about 20 degrees LOP at 9500, which is normal for me and never an issue prevously. Rolling back the mixture to well ROP did NOT bring the #1 EGT back up from zero nor did the engine roughness change until the mixture was richened almost back to full rich at 9500.
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