hello all- i have a 96 f-350 351 4x4 220,000kms a few things i would like some help on.i used a code reader to find out check engine light.this would go on with a load up moderate hills and go out when motor shut of ,and back on next time i would go up a grade. no grade no light on?.koeo no codes except for coolant temp high or low,i have a after market dash gauge with sep sender.stock sender still pugged in and attached to coolant pipe outside of piping.also dtc said o2 lean. the tail pipes are dark.not good mileage. recent plugs cap rotor wires. i changed the o2 sender, the engine still has a shakie idle.koer no codes only says inefective rpm change on test. i did put it to the floor when asked ,i did this three times same answer. when waiting for any codes no codes but the red light for emmisions comes on. towed recently for the first time with a single axel car trailer this truck seems to have less power than my old dakota with 3.9 engine with same trailer. could the cat be plugged?if so how do you tell.as well the ac clutch does not engage i can turn it by hand all fuses look good. thanks for your time.

 

Sometimes when the AC system has lost it's charge the clutch will not engage. check the freon pressure. Good luck.

 

ok will look at the freon pressure. any one have an idea what would cause the red light to come on for emmision fail? where to start looking. it is a stock motor all smog items still on the motor.is my explanation to vague? thanks