thebes

Hi Everyone,

I've benefited from the informative posts on this site for several years now, but I haven't posted before. My beloved 2000 GS300 is surging on idle, from about 600-2000 rpm with a cycle of a couple of seconds. Just before the idle surge started, I had codes p1120 and p1121, and the car went into limp mode. It was driveable in limp mode (so I could get it home), but with the idle surge the car is not driveable. (I tried putting it into reverse and left some nice tire streaks in the driveway). I removed the throttle body and cleaned up the carbon deposits. I've checked the resistances on the accelerator pedal position sensor, the throttle position sensor, and the throttle control motor - all are in the correct range. Now it's time to start replacing the sensors. But I'm puzzled by the idle surge. With the Gen1 cars, the usual solution to idle surge is to replace the idle air control valve (IACV), but I'm not sure which of Gen2 sensors is performing the same function as the IACV. Maybe the throttle motor. Before I start buying sensors, I was hoping that someone here may have had this problem with a gen2 car before. Any thoughts would be greatly appreciated. I haven't measured the engine vacuum yet, and I'm not sure that I can with the idle surge, but the hoses are all in place and look to be in good (but not great) condition.