I'm going to try and slowly work your thinking as to what part is good or bad. Say we have a stuck unit. Most units run in an analog read. Like a kid working a room light rheostat watching how dim to bright the room goes.
So we have this 0 to 5v read = Analog.

Once that IAC/EGR is stuck, it reads one number = ECM sets into more of an "Open Loop" as opposed to normal, 'closed loop.' The ECM expects a rheostat type multi number read to appear and then sets a code because it [is reading a stuck IAC number] now. The ECM takes over for that sensor.

See how you said you by-passed the unit is because the car is running on a limp mode to compensate. So, you really did nothing you think you did. The ECM was one step ahead of you and now you are locked out of trying anything else.

How are you going to over-ride the IAC? Hold a rheostat and match throttle positions? If you solder some sort of resistor to it like ModernMustang.com does to their CEL's is use a resistor? Is not one resistor a single voltage and not a rheostat like the IAC or the 02 sensor in the exhaust?

So, you have to remove that IAC unit and clean the ports (in the manifold) that may clog the underside is what you cannot clean. You would have to remove the unit completely. So, spraying the unit on one side may move the carbon goo [soaking the other side] and it may read a few extra signals until it sort of locks up or re-CEL in a few seconds, sending out that single voltage read and here comes the code or CEL (check engine light) again.

These are sort of the steps taken to set the CEL on your dash. That makes me think that if the internals [of the IAC] to send that signal to the ECM can shut down the CEL, then the unit is good. Because it sounds like/looks like it is working but needs a better cleaning, not replacing = Most of the time, I would imagine is lift it's arms up and left lower cheek is really get in the corners with some carbon cutter/carb cleaner type liquids and give it a good clean bath.

 

well check you throttol position sensor, i think thats ur problem

 

TPS is hooked up to the throttle plate. Not too many sensors move if bolted down. Same as saying you can move the electronic tone wheel on the crank? TPsensor would spit a code, I think if it was out of wave count. It's complex and you would not call the TPS with that kind of backup is the code, the wave length read, the idle to WOT would be way off, she codes if things go bad with the TPS.
OK, if you move the TPS from factory setting, [like, you had to move it and just threw it back together]? Yep, TPS is out of wave phase is all. But will it spit a code being that bumpy within the window or out? Get it?

 

how do u bypass the EGR?

 

I dealt with this today too. Took the TBI off and polished it up the other day, over tightened the cable side and played hell with it to open properly. Got codes for P0122, the TPS of death low voltage code. Apparently putting it back in i didn't get it aligned right, so I did it again. Car ran fine, then went back to walking death. I brought it back home, grabbed the contact cleaner, took the wires out,took the TPS out, hosed them both down, and while dripping wet, put the TPS back in, set correctly, and bolted it down. Then I unplugged the battery from the car and walked away. I came back 10 minutes later, turned it on, sounded fine. Drove 3 miles to the Autozone I like up the road. No problems. Had them check the codes, all ones I knew they'd be, and erased them. Came back home. Later on, drove out, went up the main street, down a few back roads, got on the freeway for about 4 miles and came home. No shakes, quakes, horks, or hairballs.

 

Ok... EGR valve is used for nothing but emissions. It takes hot exhaust gases and throws them back into your intake to cut down on pollution. My car was already in limp mode. Easily told from the rough idle, loss of power, poor gas mileage ect. I had taken my egr valve off to clean it up to un stick it per say. I put it back on there was no change. There is a exhaust hose going into the egr valve and one coming out of the egr valve going into the intake. I simply used a hack saw and cut the hose that was going to the intake from the egr valve off and crimped it shut so i wouldn't have a exhaust leak under my hood. Right after i did this, i started my car only to hear it running beautifully. I simply cut out having to buy a egr vavle by pass kit which they also sell.

Hope you can understand...lol