The 'ol Check Engine Light-coincidence?

[lskrogers]

Any ideas? I have a 2000, Ranger with the 3.0, Flex-fuel engine-85,000 miles. The 3.0 has never been known as a "neck snapper," but mine seems to be getting slower and slower. However, it runs as smooth as a watch. There are-or were-no codes. I thought I would start with the easiest fix and that would be to change the plugs assuming the ones in the truck are the original. I bought new plugs from Ford and checked the gap-all were correct or were re-gapped to the correct measurement. CAREFULLY removed one wire at a time and replaced the plugs. Used tune up grease, minimally and felt a good snap when reattaching. For the sake of brevity and not boring any readers, please assume I did everything correctly. Truck started fine and I assumed all was okay. No check engine light on.
I drove the truck the next day, probably 50 miles at a minimum and then went to work the following day. Going home, 75 miles later, I got a block from work and noticed that the check engine light was on. Checked the gas cap and it is on tight.
So is it just a coincidence which I doubt or can somebody think of what would be the most likely cause for the check engine light to come on so close to just changing the plugs.? Not that I could have missed some thing, but I've looked for loose wires, changed air filter and I don't see anything obvious?

Any ideas?? I'm open to anything!

 

[bikerboy]

Get the codes pulled for us so that we can see what the computer is saying. Many autozones will pull the codes for free and be sure to get all the code numbers and descriptions.