Hissing noise while gas pedal is pressed down

[bix]

Hey everyone, ive noticed lately that i have a hissing noise whenever the accelerator pedal is pressed and then seems to dissapear when its pushed to the floor. Im also running rich and getting very bad mpg. Has anyone diagnosed this before??

Thanks for the help, i can turn wrenches but im no mechanic

 

[Kain]

what the motor,carb or fuel injection?

 

[bix]

Hey sorry. Its a 1990 k5 350 tbi, sm465 np241 with 245k km.

 

[Kain]

the hissing is weird but the mpg could be 02 sensor gone bad. have you checked the codes

 

[bix]

Yea im on the hunt for the richness. Ive had alot of help on here from guys. Ran in circles chasing things so im going to bring it into a shop or buy a usb connector and check whats going on everywhere with a live data scanner since i cant figure it out. Just noticed this hissing noise now so im wondering if anyones had that issue before

 

[Kain]

The hissing could be the vacum on the heater controls come loss

 

[bix]

would it be hissing all the time or only when the pedal is pressed.

 

[Kain]

dont know i would check it just to eliminate it as a possibility

 

[paratrooper307]

A vacuum leak generally hissess all the time, but may get more pronounced after you hit and release the gas, as on a healthy engine it will momentarily drop and then shoot back up. A vacuum leak will generally cause a lean condition, which may lead the ECU to overcompensate with more fuel.