Hi...my '90 Civic DX (1.5 Stock) idles in neutral up and down between 1100 and 1600 rpm's and the exhaust fumes smell very rich. Not sure what this can be. It did this 2 weeks ago for a short period of time but it then went away. Can't find any vacuum leaks and the radiator is topped off. My Civic does this when the engine is cold and warm, so it is not thermically related.

Are there any Civic experts out there that can give their input on this...would be very thankful.

M.

 

Same thing is happening to my 90 civic..I just replaced the throttle body so idk I that's the cause? Can anyone help??

 

Cleaning the IACV helps with Idle problems. I'm also having Idle problems on my '94 DX and I have cleaned the IACV.

 

Start by unplugging the IACV wire. If it slows down, the ECU is commanding the high idle. That is usually because of false readings from the ECT sensor. Make sure the cooling system is full.

If unplugging doesn't change anything, pinch off the hose that goes from the side of the air box to the manifold near the IACV (it supplies air to the IACV). If the engine slows down the IACV is stuck open.