My 1992, car starts, but high idling

[summersky1984]

hi, I have a 1992, the car starts but high rpm (2.5prm), it goes down to 1.5rpm and up a little, and down a little, and up a little, etc. I drive it for around 10 minutes but at high rpm before it goes back to normal which is at .9rpm at neutral, any advice would help, the car has no exhaust which I will buy and put it on soon, and aftermarket air intake, I just recently bought it.

 

[Kitaka]

The exhasut system includes the emissions 02 sensors. These sensor help with managing engine rpm and fuel mixture. You need to have them active when evaluating your problem

 

[cmthomson]

This is also consistent with a dirty intake air temperature sensor, a notorious cause of running rich and failing smog.

Read this thread:
http://www.nsxprime.com/forum/showthread.php/159564-Is-your-NSX-failing-smog-Read-this

 

[summersky1984]

thanks for your help, yes it so weird and I can't seem to figure it out.. the car starts, but idling high at 2200 to 2500 rpm, a few minutes later, it goes down to 1500 rpm and back to 1700rpm, up and down, etc. once I drive it off, 5-7 minutes later, it goes back to normal idling neutral or parking at .900 rpm, so its the air intake temperature sensor? thanks

 

[cmthomson]

Welcome.

Another guess would be the thermostat. When mine screwed up a few years ago, the idle was wonky, the temperature gauge stayed too low, and my mpg tanked.

Cleaning the intake air temp sensor is easy (and free if you do it yourself), so definitely worth a try.