on a 3.8l just rebuilt the engine so first time run. it idles okay and is fine untell about half throttle then it starts backfiring and gets worse the more throttle applied.
First thought that comea to mind might be a fuel volume problem. Not delivering enough fuel at higher RPM.
Second thought was what happened with my boat.
Timing was retarded. Even though when checked with a timing light it showed bang on it wasnt. Advanced timing and ran well through full RPM range.
