strange off-idle issue

[sportlineguy]

I have a 2001 996 tip with 40k that has developed (or I just noticed) a slight idle issue.

In gear stopped I can feel a slightly rhythmic pulsing but the rpm is very steady- it is the same in park as well. but if I just touch the gas to bring rpm up to @ 1000 it pulses up and down @ 200rpm each cycle. The car drives normally and it is not something that affects drivability but wondering what it is.

New air filter, new fluids, well taken care of and no codes popping up. Top tier gas used, and no oil usage between changes at every 5k.

Should I try a spray cleaner into the throttle body to see if any buildup - but it looked very clean when I changed the air filter recently. ICV possibly or an intake leak of some sort - what is the best way to test this?

Thanks for any ideas to resolve this minor issure - before it might turn into something larger...

[P2C4]

I recently had similar symptoms, but with a 1999 C4 at over 140K miles. Try cleaning he throttle body, and the mass air flow sensor (with electrical spray cleaner). It sounds like an leak in the air intake system (which is what mine was). Indy mechanic uses a smoke system to check for leaks. Wasnt' that expenseive to diagonse and fix. Make sure the oil cap is on tight, and fits tightly (mine also required some smoothing of the interface where the oil cap screws on).