Here's what I have. A 96' ranger 4.0. I replaced plugs and wires about 5000 - 7000 miles ago and I have a new fuel filter that I am planning on taking care of this week or so. I do have a check engine light on for the egr system and I was told that the tube that runs from the bottom of the egr valve should be taken off and cleaned out and the egr sensor also with carb cleaner. Could a check engine light cause my truck to run differently and can a fuel filter have that kind of an impact on idle?? Any help would be greatly appreciated. Thank you for your help!

 

change the fuel filter, but also check the gap on your plugs (and the brand!!). I put Bosch plugs in my '99 yesterday and now today I'm taking them out in favor of Autolites. At least that's a cheap and easy test.