Ford Repair: 1994 Ford E-350 5.8L

Question
how you doing i am  having lots of trouble with my van it has a misfire while driving and at idle ittermitenitly and cant figure out from where i have changed many parts such as cap/rotor/plugs/wires/ ignition coil/ pick up coil/ tps sensor/it runs fine the sputters really hard out of nowhere i bought this vehichle used with the problem thinking it only needed a tune up and i replaced all the parts and its still the same it only has 107,000 mils i was going to replace the mass air flow sensor but i cant locate it for the life of me

Answer
This vehicle has a bad problem with the catalytic converters. When going bad, the van will run erratic until they clog up for good, the the vehicle will lose power. I would have the converters checked. I believe there is three maybe four converters that have to be replaced as a unit. Good luck.
Jeff