Loud mechanical backfire noise/feel THUMP? Porsche boxster
 

anyone know what this is?

was driving a 986 boxster s 6 speed manual and whenever i would lightly apply throttle in any gear, i would get a loud THUMP noise from behind/near engine trans area. i thought it was a backfire cause it was so loud. it would just happen one time but only when throttle was applied, and only during acceleration.

thought it was motor mounts, but no vibrations while driving, and while at idle when i would rev in neutral, it wouldn't shake or make the loud thump noise. checked exhaust and suspension but both of those were good.

is this a transmission issue? or an engine issue? thanks

Front engine mount

When I first got my '99, the engine would slam fore and aft on taking off or stopping hard. All mounts replace cured it.

thank you for the responses all!

my initial thought was for engine mounts. that said, there is no vibration at all, and when i rev the car in neutral, it does not make the thump noise - is this still indicative of bad mounts?

I think it could still be the mount(s). They are probably just ok enough to dampen the vibration at idle, but not enough to take the intial load of acceleration.

When my mounts were bad, you could feel the shifter move forward and back (accompanied by a slight clunk) when I hit the accelerator from a stop. The slack in the bushing was pretty noticeable, but I didnt have any vibration from it.

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