[jss06c6]

Got the TB reinstalled and fired up the engine. It settled down to about 900 rpm, cold and in open loop. Let the engine warm up and it dropped down to my "normal" 750 rpm in closed loop. Got the laptop, launched TunerProRT and began to log the engine. I replaced the throttle set screw with a hex head and lock down nut. Installed it the same offset distance as the original one I removed. IAC sits a 0, versus previously at 4 with a hot engine. Have not set minimum air yet, but will get that done with a warm engine.

Took the car out for a drive. Each time I came to a stop, the engine would idle down to about 700-750 rpm and IAC would return to 0. Throttle position at 0.53 volts.. all good. After about a 5 mile test drive, I noticed the idle was again about 1200 and hunting again. AFR was swinging from about 13 to 15.5, not quite same frequency as normal dithering. Let it sit in the driveway for about 5 minutes, idling, no change.

I pulled the bellows and got a piece of cardboard to block off the TB. Took about 5 seconds before the engine began to bog down. I let it get to about 400 rpm and then pulled the cardboard off (difficult with that much suction!). The engine RPM came back up and the AFR was now swinging pretty hard from 12.5 to about 16.5, but the idle was now back to 750! Repeated the sequence two more times with the cardboard, with same results. IAC still at 0 at idle and TPS still at 0.53 volts.

I'm going to try to set the minimum air this afternoon while I've got good weather. I looked very closely at the TB when it was out and I cleaned it. There was virtually NO light coming past the TB blades. Only spot was near the shaft on one of the blades and this was extremely small. There is no DAG in this TB. Makes me wonder if this TB has been worked over in the past, possibly by Marc and prior owner had it with him..

So, I've either still got a small vacuum leak under the plenum, or the TB is allowing some air to pass through at idle. The fact that after the TB was blocked off caused the idle to return to 750 causes me to think that a vacuum hose connection may have been leaking slightly and the increased manifold vacuum "pulled" the connection in enough to re-establish integrity?? Don't believe the TB was sticking, it was clean and free. I put a very small amount of oil on the shafts where they come through the outside of the TB casting..