Hangar Flying

Thanks for the insight. I difinetly will continue to look into all the suggestions and hopefully isolate the problem as you suggested. I'm forutnately have a good A&P familiar with the engine, but not with the electronic ignition system. One peculiar thing is that after we calibrated the carburator for idle and max throttle, after the flight, the idle RPM was a lot lower when I landed (at the same setting) and in the first instance the engine quit while exiting the runway. That also happen yesterday after the second test flight, while bringing it to idle, the engine sputtered substantially and then it quit. ? Thank you very much for your time.

Afif

I own a Long EZ that has a CDI system (2 coils and a magneto) and has been flown close to 400 hrs with it. Since I didn't build the aircraft, I've  invested time and effort studying ever aspect of the aircraft. I would like to share my experiences with your expertise and hopefully we can identify the inconvenience I'm having right now.
 
While flying my airplane I've noticed every now and then a "thump" which ususally makes my heart skip a beat. At the beginning I thought it was maybe moisture on the fuel or bad fuel, however, the problem has not gone away. After experiencing some engine roughness on a flight around 10,000 ft, I was suspecting tht my carburator of my Lycoming 320 engine need an overhaul given that I didn't have supporting documentation that any service had been done to the carburator. I ordered a new carburator, spark plugs &cables were in good condition, no visible moisture on the coils, air intake clean and with good integrity, etc. We did all the calibration to the carburator and I took it to a test flight. To my surprise the every now and then "thump" didn't go away, but the engine run pretty smooth with the new carburator. Trying to troubleshoot this I am looking into the CDI systems to be able to understand it better and try to determine if the CDI might be a "suspect" in this case. Is it possible that the coil might not be giving the proper charge to the system while in running mode? I've discarded the magento because every amg check is smootha and on tolerance. Do these coils loose efficiency over time? Should they be replaced?
 
Thanking you in advance...

Best Regards,
 
Afif E. Saybe, LONG EZ, HR-ATQ
President
Saybe Engineering S. de R.L./Honduras