Probably a dumb question (or not)......Can a faulty gas cap make a 4runner 3.0 run rough. A friend of mine has a Ford F-150(I know), which was running terrible. He took it to the dealership and they said it was a faulty gas cap. O f course he thought they were *&$@*%#, but it turned out to be the problem. Just wondering if this is true with Toyotas??

 

If the gas cap doesnt make a good seal it could be possible. But it could also be the fact someone didnt tighten it down enough.

Always when you open the cap a whooshing sound should occur-thats pressure leaving the tank.

 

Mine makes that sound, but not all the time. Whenever my tank is low, it seems to run rough. Then when I fill the tank, it seems to run better. I fill my gas myself, so i make sure it's always tightened.

 

we'll have to switch to Chevys.

Any how I've never seen anything like this on a Toyota.

 

The fuel system is designed to be pressurized. If it runs rough while low on fuel its probably got some restriction. It would be worth swapping the fuel filter if it hasn't been done in awhile (or ever)

 

I changed the fuel filter already, I'm wondering if the fuel tank vapor vent hose could be the culprit.