First off, if this is only for tuning, sorry and please move to the appropriate place. Now heres my situation

Bought this civic from a friend a few months ago. Its a 97 civic hx manual with 220k on the clock. Gave it a pretty big tuneup when I first bought it. All fluids, plugs wires cap rotor, egr chamber plate. I also cleaned the throttle body and the IAC sensor. I drove the car a thousand miles and it ran absolutely great getting 40 mpg. Then, she started revving high when I would start it. LIke over 2500 rpm. Sometimes it would rev up and down when I first start. Also started bucking when in gear and off throttle. Threw code P1508. I pulled the IAC sensor again and cleaned it. I also put 12v to the sensor on my bench and it clicked and I could see the plunger moving. Put it back on and problems still existed. I just pulled another IAC out of the junk yard and cleaned it and put it on, cleared the codes and its still running poorly. Code is not back yet but symptoms are. Only drove it a few miles. Now there is an oring that goes between the sensor and the manifold where they meet. I did not replace that. Also could the alcohol that I cleaned the sensor with be making them fail? 91% isopropyl alcohol. Also, does coolant need to be bled for IAC to function properly.

Thanks

 

Yes, coolant should be bled.

Have you checkd for vacuum leaks around the throttle body, intake manifold or surrounding hoses?

 

I have not checked for vacuum leaks. I will look now. Would a vacuum leak present most problems when the throttle is open since the vacuum will be higher then? My issue is only when off the throttle. ALso going to bleed the coolant.

 

Delete

 

bled coolant, checked for vac leaks. Reset computer and did relearn procedure. drove fine for 30 minutes. Then light comes on and drivablity issues return. Starting to get annoying.