1996 thunderbird v8....if i fill the gas tank full or take the gas cap off the check eng light goes on...gets down to 3/4 , light goes off....and when it gets to 1/4 comes back on...any insite on this one? reset computer but with no luck....could a faulty gas cap do this? most tell me o2 sensor....

 

It does seem like it would be a fussy gas cap. But don't guess. Go to autozone and get them to check the codes in the computer (they do this for free) post the codes here and hopefully one of the pros can tell you what it means (BTW it could be the O2 sensor and it could be dozens of other things so don't throw parts at

 

MANY dozens of other things,

start with the actual code