I am new member to this forum, first post, hope somebody can steer me in the right direction.
Here'* the situation: 94 Bonne SE
A few days ago my Check Engine Light came on, along with the Traction off light and my speedometer no longer works. My Immediate thought was "It'* just a glitch" So I pulled over shut the car off and hoped for the best. Wouldn't start without a jump. After I got it started, I took off, but still had the lights, no speedometer, I headed on down the road and the speedometer came back for a few miles and then went away.
Along with this I have a high idle, sometimes a tolerable 1100 but sometimes it races to as much as 2500 or so, not good.
I drove the car over to a good mechanic to have the codes read. His computer could not read them, nor could the one at AZ, and Advance. The mechanic did a little tinkering and caused the Idle to go up while tapping on the throttle body and was quite sure the IAC plunger was stuck. So I swapped throttle body, along with the IAC, TPS, and MAF from my '92 which ran perfectly everyday it was in service (frame and body rusted). No help.
Also I put a new battery in, since the old one was shot. I think maybe this may have started or led to some of these problems, but not sure.
Any suggestions greatly appreciated. I have a complete parts car so swapping parts to test is no problem.
Sorry for my wordiness.

How log did you let the car sit with out a battery while you were swapping them out?

I would almost reccomend disconnecting the negative terminal and letting it sit, say overnight and see what that does. The computer is working, or part of it being that it does start and run, but does not answer to whay everything else is acting funny

I unhooked the battery for at least 1 hour while swapping the TB. That should be sufficient to clear the codes and reset the 'puter. Or not??

When is Pat heading back to Pitt? I'd like to see his scantool on this car if he has the 16-pin cable for it.

Just to clarify, I couldn't ever read codes. I think it is an odd year with mismatch computer/test port. That is to say, I think it still is OBD1 with OBD2 test port. Can anybody verify that? or tell me how to find out. Anyway I dont think the computer is "fried". If so the car wouldn't run at all. Any other way to read codes? Like my '92, just short the test port and count the blinks.
Cheetah, Thanks for your quick reply.

94 SE, I'll put that in my Signature. any other info. that should be in there?

I had a very similar problem. I have a 95 Bonny and the idle was all over the place and the speedomter quit. Check engine light was on. To make a long story short after changing all the sensor, checking a million grounds it turned out to be the computer. $100 at autozone and it drives like new again.