I am having problems with the idle speed on my 1990 240sx. From time to time when I come up to a stop light, the engine RPM’s will drop drastically and the motor will shut off. The same thing happened while shifting. As soon as you take your foot off the accelerator, the RPM’s will drop from to zero.
In addition to that, when the car is sitting idling after warm up the idle speed is OK but it does pulse or fluctuate a little bit.
Any ideas what to look at.
What you got KA24E or SR? It might be the MAF on either engine or if you have SR, could be a hole/leak in the intercooler piping.
Check your MAF and IAC valve.
Thanks for your suggestions. It is a KA24E motor.
IACV FTW…
Spray some carb cleaner on it/around the gasket “while the engine is running” and if the motor revs up, the gasket is leaking"
You may just have to adjust the idle (usually is beyond that)
Last thing would be to remove the IACV and give it a good cleaning out
But, the IACV might be toast as well (good chance it is)