I have been experiencing this weird RPM dropping during cold start.
I would start the engine in cold and it runs around say 3500 RPM. After couple of seconds, the RPM drops suddenly to 3000 RPM. Sometimes it raises right back up to around 3400RPM.
What could be the problem?
I changed the spark plugs about 3 years ago?
I changed the engine oil.
JWT intake. Just cleaned the filter.
I have a 350z with g35 stock exhaust.
Plenum spacer.

 

Dirty nasty throttle body. Usually only does that when its warm. Must be mucked up pretty good.

 

i have done it once about 2 years ago. I guess I have to do it again
Would it be fine to clean the TB while connected to the engine, if i disconnect the battery and TB connector?

 

Technically they say no. I've done it and had no problems. I cleaned it hard; opening and closing the throttle body over and over again. Apparently this isn't OK, but that was about 2yrs ago and haven't had any problems. Worse comes to worse you gotta do a reset. No biggie.