Running rough? Tried everything? Check this out!

[4RunninElgin]

About a month ago my 93 startedrunning rough and rich. I have mad my way through the list of possibilities and went to speak with the local mechanic. He noticed a little oil on the top of the valve cover. He checked the connections of the vacuum lines and then pulled off the oil filler cap. No change. He then put his hand over the filler hole and the engine perked up almost immediately! He told me to replace my filler cap because it was leading air. We all know how important it is to keep a good vacuum. So that could be the answer to your problems! And the best part? Cheap! I also noticed after doing this the hissing noise at the gas cap when you open it had returned! Awesome! :bigok:

 

[dorton]

You can test your gas cap also(or at least people with evap testing equipment can). I had a vehicle come in for a fuel leak a few days ago. The fuel cap is supposed to only hold a certain about of pressure or vacuum. Testing the cap, it would not release even at 20psi. The tank had been blowing up like a balloon, and then sucked back down until a spot fatigued and caused a crack. Even little things can cause big problems.