I have a 91 rx7 non turbo. I just bought it about 2 weeks ago off of a guy on this forum. I used to own a 87 N/A and that had to go and I just really wanted another rotary. So I got this one. Any ways. I start it up and it goes to about 3.5k to 4k rpms which is good and then it will go down to a pretty steady 800-1000 rpms but once i start driving and its a little warmed up, if I come to a stop the idle will drop to like 500 or lower and it's almost died a couple of times. and when it's really warmed up it will jump around from 400-800 rpms. Is this TPS? What could it be and is it a easy fix?

 

TPS is a good start. If the car is in need of a tune up ( air filter/oil change/plugs ) i'd get that taken care of then check the timing and for vacuum leaks.

 

Ok thanks. The guy said its a brand new rebuilt engine from mazda. And that it will need a oil change soon. Theres only 130k on chassis and the engine does appear to be new. So ill go ahead and check that tps then do a tune up. What oil do you recomend and spark plugs? I know not to go with synthetic because it ruins apex seals and I heard NGK's are the pretty much the best.

 

I usually use Castrol 20w-50. I'm not sure about the synthetic ruining the apex seals, but you still have your OMP hooked up so it's probably not a good idea to have it injected into the motor. And it's not really necessary on a stock FC.

NGK's are good and what I usually use.

You can use synthetic in the motor, but it's widely debated which kind is best. I'd do my research before I put any kind in, but Idemitsu is a good place to start.

 

Low/variable idle can be due to a lean mixture at idle, which in turn can be due to a vacuum leak. Check the O2 sensor voltage while the problem is present. If it is less than 0.45 volts, the mixture is lean. Could be just the idle mixture adjustment, or a vacuum leak, or both.