Car starts right up but idle is rough. Soon as the car warms up drives and idle is normal.

Reading temperature sensor is culprit. Sound right? Everything else in engine compartment is normal.

2002 no mods. No codes.

 

https://www.s2ki.com/s2000/topic/492...ean-iac-valve/

IAC could be sticking when cold. Here's a write up

 

The IAC when removed looked clean. So I cleaned it anyway. Put back together and problem is still there.

Any more suggestions?

 

It takes a bit after three bars before smooth. So it has to be at three bars for awhile.

 

When cleaning IAC I noticed OEM intake has cracked and broke off near throttle body. I replaced whole intake with a k&n cold air intake I had previously for the S2000. So th K&N is on now.

The issue seems to be getting worse. But eventually stops after car is fully warmed up. The car runs as it should after it is warmed to temp.

When I start car in early morning it is 67 degrees or so and when I start car after work it is 77 degrees. So its not cold in regards to ambient temperature.

I will pick up a temperature sensor.

Anything else come to mind?

Thanks!

 

Appears head gasket is going to have to be replaced.

 

Why? Low compression? Oil in the coolant, or coolant in the oil?

 

Coolant in combustion chamber.

 

I the oil as well? Or blowing out white smoke regularly?

 

Honestly I see no smoke and I had a shop do the diagnosis. They say there was rust and coolant on spark plug. They say there's a small leak then burns off after awhile. Kinda makes sense.

I did not do the work or actually see spark plug. I tend to believe their diagnosis.

I changed oil two weeks ago and didn't see coolant in oil. No smoke. I have second car not in a big hurry. I will be contemplating my options.