I have a 1995, 4.9L with 372K miles. I did not pass my last State inspection due to high HC and CO. I have noticed that the truck seems to running rich. I can see sooting from the tailpipe and reduced mpg. Check engine became intermittant about one week ago. It would come on during acceleration, or sometimes when slowing down. Any thoughts?

Thanks

 

Have the codes read and post them. With emmisions, high HC is caused missfire and high CO is mixture, go after the missfire first as unburned fuel will read as high CO. The one might fix the other, plugs, wires, cap, rotor are all things to consider.

 

Thanks, Good old Bill. As soon as I can get the codes, I will post them. Plugs, cap, and rotor are about two months old. I did not change the wires, and I can't recall the age of this set.