Crank Angle Sensor???

[red 300zx]

So i put an na JDM motor in the z and it runs great,well except for running at about 1400 rpms. My question is, i was driving it a week ago and it cut out no spark, scanned it and it said it was a bad cas. So i got a junk yard one and it fired up then quit again, so i cleaned the plug and its been starting just fine but still running at 1400 now it dips to 1100/800 sometimes what could cause this?

[robomatic12]

Are there any ECU codes now after replacing the CAS with a used one?

So am I correct that you are saying at idle the engine is running at 1400-800rpms? Check for vacuum leaks and adjust the TPS (throttle position sensor; search for a guide, theres lots) and then set the IACV (idle air control valve). You may need to clean/replace the IACV for a steady idle if it's gummed up.

[red 300zx]

No more codes, could the tps cause irratic rpms?

[BigTDogg (MA)]

No more codes, could the tps cause irratic rpms?

I don't think so, but a bad/dirty MAF would.

[Rich@RDZ]

At this point in the history of the Z32, All original parts are suspect because of the known corrosion problems with them. It could be many things, BigTDogg is right try cleaning the MAF (with Maf cleaner), TPS probably not since at idle it has a problem. IACV is suspect. If EFI harness is original, well, it could be most anything because of corrosion. Is the PTU sub-harness new? known to corrode. Yes, there is a trend here.

Keep with it you'll find it

[es.biggs]

Wouldn't hurt to check the TPS...it's not hard. Just need a multimeter and a needle or a small nail.