January 23, 200917 yr i've read several past posts using search but I still am wondering about the sequence of operation of the IAC. I have idle surging 1000 to 1200 after the car warms up (94 loyale spfi) I have checked my IAC using the fsm and it checks ok, I have cleaned it and also tried a junkyard control with the same outcome. my question is, after the first minute does the valve stay open all the time? when the idle is surging I can cover the inlet to the IAC with my thumb and the idle smooths out and is normal. I am getting a code for IAC and O2 sensor (O2 sensor has less than 2000 miles on it) I don't mind buying a new one I just want to make sure that i'm not missing anything . Thanks for helping !!!
January 23, 200917 yr The o2 sensor code may just be, because the car is running too lean. Befor you go any further did you try all the standard stuff first? Did you run with it unplugged? That will throw your code. Did you check for vacuum leaks? How bout the PCV? The temp switch should throw its own code... Did you check the o2 sensor and its wiring? what did the code say exactly? Doubt it will help, but, did you try unhooking the battery for a bit? Or at least clear the codes, see who comes back?
January 23, 200917 yr Author the pcv valve is new and I have checked the temp sensor, seems to be ok. I am going to do a thorough check for vacuum leaks this weekend. thanks!
January 24, 200917 yr Author still fighting this one, I went through all the hoses and sprayed wd40 around the intake, couldn't find any vacuum leaks. When the idle is surging if i disconnect the rubber hose from the iac the idle smooths out, also stays smooth if I cover the iac hose inlet(can feel vacuum on my thumb) the second I reconnect the hose the surging starts and continues. anyone have any thoughts or suggestions? thanks!
January 27, 200917 yr The IAC is mostly for cold-idle. It's basically a solenoid valve and you need to verify not only that it's working but that it's getting proper voltage. It may be getting a poor signal due to a high-resistance ground or connection in the harness. A bench test will tell you if the valve works (pulls in and stays in), and then you need to check the voltage in the car. Beyond that there is an adjustment for the IAC port in the throttle body on the side of the TB - looks like a big flat head screw that's recessed into the body. That is how the idle air port is adjusted and you may need to close it off some. Additionally, make sure you haven't adjusted, or someone in the past hasn't adjusted the throttle plate stop screw. That is NOT the idle adjustment and should never be moved or adjusted in any way. There should be a white paint mark to indicate it hasn't been moved. GD
January 27, 200917 yr Author thanks GD, I did verify proper voltage in the car but I will definetely experiment with the air adjustment. I appreciate the reply!! steve
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