Knocking when goosing the throttle?

[omeara7]

I noticed that when I goose the throttle from the engine bay (with the throttle body) I hear a knocking noise (only about 2 knocks then it stops as the RPM rises). It sounds like a cam or something similar to a valve tap. When goosing it, I also hear air being sucked from where the runners meet the head. This makes me think the gasket isn't lined up right. Any ideas what this could be? Thanks
(95 MTX)

 

[zpyro]

seems like you have a vacuum leak, causing a lean condition, causing it to knock

 

[SASHO91]

have the rod bearings been changed? obviusly that wont cause the air noise you are hearing... but that might be a sign you RB's are going out...

The air sound you hear may be from the secondary couplers... try wrapping your hand around them one at a time to see if you notice a difference in sound... it could be the intake to head gasket may be leaking.... but without pulling the intake and putting some RTV (a light coat) you wont be sure on that one...

If you happen to smoke.. you could always blow smoke over the intake manifold and see where your vacum leak is...

 

[zpyro]

or spray carb cleaner or other similarly flammable vapor and see if the idle goes up at all

 

[Slo-Sho]

If it sounds like marbles in a tin can, then it's called "pinging". Probably from mucho amounts of carbon in the combustion chamber. Try going up a grade next time you're at the pump.

 

[omeara7]

Thanks...the noise is definitely coming from up top somewhere so I doubt it's anything to do with the rod bearing. Like slo-sho said, it does sound a little like marbles in a can so I'll get 93 octane next time. I'll try that carb cleaner test for the runner-gasket (I don’t smoke). Thanks for the suggestions. I've also noticed that the car feels very sluggish when the engine is warm and I give it more than 1/2 throttle (mainly noticed in 2nd gear) but once the secondaries open, the hesitation stops and it feels strong again. IAB valve? The air filter is new so maybe fuel filter? I should get a fuel pressure gauge and test the fuel psi.

 

[SASHO91]

wouldnt hurt to change the fuel filter...

run some injector cleaner as well... i'd recomend the Lucas stuff... works very well....