I was experiencing unstable idle on and off since I got my fc3s. I checked previous threads and most problems seems to be TPS and vacuum leak. However my case is a little bit different. The idle seems to be working stable for a period and then suddenly becoming unstable..I would like to hear some suggestion as to where I should look into. Thanks.

Ran

 

I'm not able to see the video, but i assume based on your description that it's hunting for idle, and it's random when it happens. A couple checks i would do are:

-double check TPS with the voltage method. It should be consistent through the rev range and shouldn't have any dead spots. Throttle closed should read about 1ohm and WOT should be about 5ohms


-check the throttle cable. If it's misadjusted it could be binding just enough to prop the throttle blades open

-check the coolant sensor behind the thermostat housing.


-check your primary injectors. While it's hunting for idle, see if you can get a long screwdriver down there on top of each injector, and listen to it like a stethoscope. You should be able to hear a consistent click on each one as the injector fires.


Hopefully that helps!

 

Have you checked to make sure your vacuum system is hooked up correctly?

 

I recently bought a brand new tps sensor and installed it, after making sure that it read correctly I started getting the same problem on mine. When I press the gas pedal when it is doing it, sometimes it will jump to 2k rpm and hold there until the engine starts warming and it falls back to 1.5k. It does that for a few cycles and then once temps rise to drop the idle further, it stops. I think we have very similar problems. I have not been able to find a solution yet.