Does evap system stop hissing noise when opening gas cap on mazda protege lx 2000 1.6l

SOURCE: 2003 Mazda Protege car is shaking When Drive and Engine light stay On

I bet it also feels like it wants to stall as well. I think my car was at around 65k and it did the same. It is the spark plugs and the coil. My mistake was going to the dealership where they charge you too much. Any experienced mechanic can do it. Changing the coil is also in the manual.

SOURCE: gas tank won't vent

Supposed to hiss. There is a pressure sensor on the tank which when bad willl let you know there is a problem. That is why there is usually a warning about fuel spray on the gas cap/lid.

SOURCE: 2002 Mazda Protege acceleration problem

I had the same problem and found that the air admission tube was badly cracked.

Since this let air enter the engine downstream of the mass airflow sensor it is not measured so the engine ECU don't send the proper amount of fuel to provide the right air/fuel mixture. At higher RPM, the vacuum in the tube is enough to close the crack and hide the problem.

I temporarly repaired it with duct tape until I get the part.

Stephane

SOURCE: Hissing noise when releasing brake pedal

Sounds like your brake booster but can't be sure until I know what kind of truck or car you have....

SOURCE: 2002 Mitsubishi Galant ''hissing noise''

I would first try to locate the source of the hissing. Try spraying some engine starting fluid around the hissing area and home in on the source. The engine revs will change as the starting fluid is drawn into the engine. Sounds though more like a vacuum as you have suggested.