I just changed to the 749 ECM for my Camaro. I was receiving IAC valve errors on the dyno. I've checked the wiring for it and everything looks OK. I followed the wiring diagrams for switching the pins from the 730->749. I'v also looked up the wiring for the 749 IAC valve and it is the same as the 730? Does any one have a pinout for the 749 SY/TY ECM? This is what I changed according to the swap documents.

E3--->E4
E4--->E3

E5--->E6
E6--->E5

 

Take a look at this post :

https://www.thirdgen.org/techbb2/sho...hlight=749+IAC

About half way down, there's a discussion on the differences between the IAC wiring on Sunbirds vs. SyTys. If you're interested in the diagrams, you should be able to find both at diy-efi.org.

A few quick questions.... Have you seen this error when you aren't on dyno? And, is this a manual or automatic? The IAC error is flagged when the ECM is unable to attain the desired idle speed. If the dyno (chassis, I assume) was in any way "backdriving" the engine, this might have contributed to the problem. (At least, in a manual transmission application.)

 

Thanks. I found the diagrams and they are different between the 2. I have mine wired as per the Sunbird. I'm going to re-wire like the SY/TY, because that's waht my chip is set for. Yes it's a manual tranny. I'm going to log a few minutes to see what happens. My car stall quite often when coming to a stop, and I think it has to do with the IAC.