1994 Ford Explorer, high RPM's at highway speeds

1994 ford explorer XLT 4dr 4 wd 140,000 miles. My explorer shifts into every gear just fine, even into overdrive. However at 55 mph the rpms are at 2200 to 2500 instead of 1900, and doing 70mph is next to impossible unless I am going downhill or I have a heavy tail wind. If I try and do 65 or 70 mph the check engine light comes on as the rpms hit 2800-3100 and goes off when I ease up on the gas and drop the rpms back down.

Is this a torque converter problem or could it be a handfull of different things?