Gas cap question...

[kjbarrett01]

I have a 2000 XLT 4.0 SOHC Explorer and notice recently that the engine was idling a little rougher than usual and that I was getting some spark knock on acceleration. I did all the usual tune up stuff. To make a long story short I found that the truck idles smoother and runs without knocking if I loosen the gas cap. Anybody have an explanation for that. I can't drive around without the cap on all day because you can smell gas and it will eventually trip the "Check Gas Cap" light. Thanks.

Kyle

 

[BrooklynBay]

Do you have another cap to swap it with? Check your cap for any grease build up that could be inside of it. It is unlikely, but it may be bad. The emissions machines in NY have a gas cap pressure test that is used during an inspection.

 

[kjbarrett01]

Gas Cap

I actually replaced the cap about a month ago. No change.

 

[BrooklynBay]

Do you top off your fuel at the gas station? Does this problem only happen when it is full, or all of the time?