Hi all!!


I'm coming here looking for help, and I'm pretty sure this is the right place . Some months ago my father bought a quad city challenger clipped wings with just 35 hours of flight in both engine and airframe. This sounds good, but the previous owner sold the plane for one reason: the engine became a headache... long story short, he bought the engine brand new, fuel injected. Since the begining the things went wrong when one side of the ignition failed and he had to replace the armature plate. At this point the engine ran well. Based on this event and on some histories on internet, he decided to get rid of the injection and replaced it with two bing 54, with the jetting according to the factory (He sent the injection to the dealer and received the bings..). Once this done, the engine start to gave problems to accelerate. He worked on it for months and at the end he decided to sell the plane to us...


The problem is very weird: If you push the throttle slowly, the engine go up to 6200 RPM easily. But if you push it in one shot from idle, it get stuck stumbling in 2500 RPM's, until you close slowly the throttle at certain point where it pick up again and you can open the throttle fast and it will go to 6200 again... In any case, the EGT goes up almost to the limit (1256F) if you stay around 4400 RPM for some time...


We have tried several things to fix this, for some months... We have tested all the combinations of jetting that you can imagine, and all the positions of the jet needle, and adjusted the mixture all ways possible... and the problems remain the same... at some point, we took two carburetors from a 503 in perfect working condition and installed on it, and the engine did the same...


Recently, we started to suspect about the timing, so we checked the manual and found out that it can be adjusted, so we moved it in all the ways possible and the things went the same...


Now we have the suspect that maybe the E-Boxes, which are suposed to be programed, could have and advance timing map for and injected engine, and this don't mach with the carb behaviour.. however, looking at the part list, the E-boxes have the same part number for both, and injected and carbureted engine...


All this being said, and sorry for made you read all this, we have no clue what to do next...


Any advice will be highly appreciated, greetings from Costa Rica,

Esteve.