ok,here is how it all started.I have an 86 IrocZ.My car had a lot of low end tourqe earlier today. It would peel out like crazy. Anyways. I was out of gas today & my car started giving out so I crused up to the local Chevron & filled up with some Supreme gas. I was out for about 2 hours with no problem. Then I get home. I turn my car off and I hear a hissing sound coming from the gas cap and the air totally stinks of gas. So I go over to see if my cap is on wrong.Seems tight enough so I decide to open the tank.When I do a fumes start coming out hard!! I felt it on my face. and it continued to fume gas quite heavily. While this was going on I decided to add a pint of oil to my car because I have a slight leak. when I pop the hood a small amount of (steam??smoke?? comes from where the distributer is...(dont know if that has anything to do with anything but it did and was gone).So I put back on the gas cap and get ready to go to work and when I start my car up again My car was/is driving Very ROUGH especially in 1st gear. WHen In the higher gears it seems ok but still.I noticed I just about lost all my low end tourqe. My car will not peel out for S##T now and my pickup has drastically reduced. What could this be. I have noticed now that everytime I open my gas cap fumes come out quite heavily then stop. Could I have just gotten a bad tank of gas or what? This problem has really frustrated me so any opinions on the situation would be appreciated. Thanks

 

Rez,

You IROC has a tank pressure control valve in the fuel system. This valve is operated by vacuum. If the lines to the valve have been disconnected/damaged, fuel vapor pressure can build in the tank. If you have a carbureted engine (you didn't say) the pressure can overcome teh inlet needle valve in the carb and flood the engine.

The fuel cap also has a pressure relief valve that is supposed to open at a pressure somewhat above the control valve. It should open as a safety relief in the event that the control valve fails. Check the cap or replace it, then investigate the pressure control valve. If you have altered the vacuum hose routings or "cleaned up" some of the vacuum lines or removed the EVAP canister from the engine compartment, you might have created your own problem. If not, make sure the hoses and valve are in good condition, and that the valve is functioning.

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Later,
Vader
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