First would like to say hello to the forum. As stated in the title I am having a misfire on my 4.7 GC. My " misfire " happens around 60-70 miles an hour on highways. I give it a certain position on the pedal and it gives me a lean pop through the airbox. If I am starting out and have the same pressure on the pedal no problems or pops. It seems to be only in higher gears. I have had computers hooked up while on test drives and results are pretty much lean 75% of time. I have replaced the following parts
All plugs, coils, TPS, IAC, fuel filter, checked fuel pressure when problem happens, nothing changes when it does. I have also NO codes at all. Light does work if codes are present. Replaced the O2 sensors as well. I have read about the Exhaust valves going bad...Possible? Runs smooth as can be otherwise. Even when it pops just have to get off of the throttle so problem stops. All help would be thankful.