How closely did you inspect the IAC valve? I had one that passed the resistance test per FSM, but didn't function as intended since the internal parts degraded over time (I think it had about 100k miles at that time). Since my car is a track car without A/C, I just removed it and set my idle speed at 850 rpm.

 

Sorry to be so late in answering this; haven't been keeping up with this thread. Problem is still there, though. Regarding the IAC valve, I had removed it, measured its coil resistance at 12.1 ohms, and squirted WD-40 in there. I also manually moved the valve back & forth slightly, to see if there was any sticking, which there wasn't.

 

My car does this backfire thing while warming up. Once warm, idle is around 800rpm. 12.6K mile car with PFC, dp, cb, intake. It started this on install of dp but very slight. Then came the cb, the popping stepped up a little. Then the intake, about the same. Once the PFC was up and tuned, the popping almost doubled. It's random, not rythmic. Car idles and run great when warm. So I got that goin for me.

 

I'm going to attack this weird idle problem starting tomorrow. First thing is to remove the EGR and cover the holes in the housing. Since this is a 1994 model, the EGR Function Sensor has to be bypassed to prevent a CEL (MIL).

I have just bought an NTE relay and will modify the PCME wiring as shown in the attached sketch. I drew this sketch (less the relay ID and terminal layout) back in "BC" and posted the schematic on this forum. One forum member PM'd me and let me know it worked OK for him. Hopefully this small relay will fit up next to the PCME behind the side trim in the cabin.

Besides getting rid of the EGR valve, the connector shell for the Function Sensor is broken, and trashing that will almost be worth the trouble just by itself.

 

Installed the circuit above yesterday, and disconnected the EGR control hose today & plugged the solenoid valve line. I didn't remove the EGR valve itself after realizing I would need new turbo gaskets and have to take off those turbo output pipes to get to it. Our 2nd car is up in San Jose until next Monday, so I quit short of a total EGR removal. But the circuit works; no stored EGR fault code after driving on the freeway in 5th gear quite a ways. Unfortunately this was not the cause of the high idle; I will have to chase other possibilities next.