Hello I currently own a 93 mazda rx7.

When the car is in neutral and I rev to about 3k the rpms drop down to almost 0 and then goes back to normal idle point....

Anyone know why the car could be causing this?

Regards,
WB123

 

do you have stock ECU?
Might check the dashpot, unless you have PowerFC then there are settings that can fix it.

 

Come to think of it, my 93 RX7 had the exact same problem. I found out that when I bought the car, it didn't have a catalytic converter on it, and was therefore running fairly lean. Ergo, I opted to snag a tuner and it fixed my idling problem.

 

Another possible cause would be your Idle control screw in the TB, or the ICS (idle control) under the upper plentium.

 

My car has done the same thing for a while. A lot of people said its not a big deal.

 

Oh yeah, is your air pump still on? I disconnected mine for something when I had the stock ECU and that caused alot of similar problems.

 

If your engine is totally stock, I'd check dashpot operation first. You may have to do some slight adjustment of the air bleed screw (do a search, there's a couple of threads that have a photo of its location) or the idle adjustment screw.