[dwcls]

After driving for over 30mins around streets (and sometimes freeway), my engine starts to make little stalling/gurgling noises when accelerating pretty good from low speeds or just WOT in like 3rd gear low RPMS (ie straining the engine).

I noticed about a week ago when going to get gas that when I unscrewed my gas cap (I had been driving for about 45 mins) there was a lot of suction and air started sucking into the tank, like the reverse of opening up an shaken carbonated soda. And it was a lot of air and suction. Lasted like 3-4 whole seconds while unscrewing the cap slowly.

I thought the two might be related (engine and gas tank suction)

So a couple days ago I was doing some house hunting (30mins+ driving) and I heard the engine make the minor "stalling" type noise, so I got out and unscrewed the gas cap, and the same thing happened...

I figured for some reason the extreme negative pressure in the gas tank is not allowing the fuel pump to pump at its optimal rate (psi) and therefore the cylinders are not getting enough fuel during acceleration.

I had the fuel pump replaced about 3-4 months ago, but have had a similar engine operation even before the replacement, but it was worse.

Is there some sort of check-valve or something on the gas tank, fuel line that allows the gas tank to let air in, but not let air/gas-vapor out? Could it be clogged/broken?

I don't know.... if you have any suggestions please advise. Also it may be time to calibrate my stock TPS as it may be off as well.

Thanks!

[Monkey Boy]

The only thing I can think of is that the vent line next to the filler neck is plugged up or capped off.