I just got this '89 RS running for the first time in five years. I ran it at idle today for 15 mins and it overheated and we got the code 23. I didn't have the air cleaner assembly installed so I'm guessing that's why. I looked all over near the TBI but I can't seem to find the pigtail to plug into the MAT/IAT in the air cleaner. I've seen pictures of the loom it's supposed to originate from but I sure can't find mine.

I can understand the ECM throwing that code when no sensor is connected but that wouldn't account for my high coolant temp after 10mins of idle would it?

I am expecting lots of issues to pop up with this project but I'd like to tackle them one at a time. Thanks!

 

I just found the wire for the MAT/IAT. Some genius had pulled it all the way back inside some insulated wire wrap. Popped it in the air cleaner and I'm about to fire it up for another 10 mins to see if I get a code and/or overheat still!

 

Pulled off the fan coolant switch wire and grounded it, fan came on immediately. Replaced the switch and the fan runs like a champ now. The wife and I drove it around the neighborhood for 15 mins just now, no problems no codes. Shifts pretty smooth, brakes well. I'm a little surprised! We have to sort out an exhaust pop from the heads/headers. A mechanic friend suspects an air injection/exhaust leak.

We also rubbed out and waxed the hood, roof and hatch. The paint isn't too bad. I'll see if I can get some pics here:

 

Glad ya got it figured out before anyone could give ya info! Good work!

 

Thanks. There's plenty of passive information to search through even if it takes a little digging . If I can narrow down the engine pop to something benign I'm going to put a few freeway miles on it as the next test.

 

Good looking car!

 

Thanks Eagle Mark!
(Not just for the compliment, but also for your help on the other thread!)
We're getting her there!