fiesta hissing noise

[goboddog]

when driving my fiesta (1.4 ghia 97 r)i get a hissing noise but only when i accelerate quite hard..i have had the exhaust tested for gas leeks but all was ok any ideas????????

[Munter]

goboddog said:

when driving my fiesta (1.4 ghia 97 r)i get a hissing noise but only when i accelerate quite hard..i have had the exhaust tested for gas leeks but all was ok any ideas????????

Remove the snake from under the accelerator........(sorry..)

[twin40s]

Could be a leak on the intake side, and your hearing it sucking air in.

If the idle speed is ok then check from the throttle body out towards the air filter. If the idle is uneven/high the leak is probable on the engine side of the throttle body.

[nel]

twin40s said:

Could be a leak on the intake side, and your hearing it sucking air in. If the idle speed is ok then check from the throttle body out towards the air filter. If the idle is uneven/high the leak is probable on the engine side of the throttle body.

Seems the most likely explanation as at full acceleration the vacuum upstream of the throttle body is maximised. Just a thought, but also check the spindle on the butterfly - possibly at fully open position a worn spondle housing is letting in air.

[Mr2Mike]

nel said:

Seems the most likely explanation as at full acceleration the vacuum upstream of the throttle body is maximised. Just a thought, but also check the spindle on the butterfly - possibly at fully open position a worn spondle housing is letting in air.

Vacuum in the inlet tract is at a minimum under full throttle, so I don't think a vacuum leak is the most likely.

Exhaust/cat blockage would be a possibility.