Misfire on a Pull

patmcclelland

We have an annoying missfire on a part throttle pull between 40 and 60 mph. The missfire is less pronounce but still occurs when the overdrive is turned off. The fuel pressure is 1 lb low at 29 when running and one lb above minimum at 36 when ignition on and motor off. What do you go after after the fuel filter? Or is it likely to be the torque converter even with the OD off. The car has 260,000 gently driven and well maintained miles?
Thanks
Pat

crownedvictor

when i had this issue, it was due to a mass air flow sensor malfunction. on the rear of the engine on the left below the intake manifold is a vacuum diaphram that has a hard plastic line that runs to your air intake assymbly .. fortunately for me it was the fact that it was disconnected that made the car either not run with the mass air flow sensor connected or i had to disconnect the mass air sensor entirely to make it run. it may also be your charcoal filter located under the headlight access panel in front of the battery just under the bumper. make sure that it isnt clogged. also these 4.6L SOHC SFI engines are very tempermental when you have a vacuum issue. they have alot of systems tied into the vacuum system. that one diaphram i mentioned earlyer was the root cause of my car not running at all with the mass air flow sensor connected. it was very bizzare. just make sure all your vacuum lines are free of clogs and are not weathered. also, ensure you do not have an EGR (Exhaust gas recerculation) valve problem going on, an OBD test should determine this. they run about 45 dollars from my local dealer anyways. you'll need an angled open ended wrench, and its a pain to get to it as it is on the back of the engine on the passenger side. the mechanic had to cut a wrench and weld it at an angle to even remove the egr. regardless, i'll bet its a vacuum issue.