Recently completed TBI to TPI conversion on a 88 305 Camaro. Converted to 91 Speed Density system. Converted from165 ECM to 730 ECM. ECM reprogramming was done by Tuned Performance so I know it was done correctly. The car runs great. However, the cruise control does not engage when I hold the button in. And, if the cruise switch is on, it will just kick in all by itself from time to time. The stalk on the multifunction switch was broken so I replaced the whole switch with a new one from Dorman. Unfortunately that did not correct it. It still won't work when I hold the button in but will kick in all by itself now & then. Any ideas?

 

Here is a 3 year old thread that might be good to look at the schematics and or ask your question.
Just curious is the cruise signal coming from pin c1 on your 730 ecm .
https://www.thirdgen.org/forums/elec...trol-87-a.html

 

I found the schematic that’s closest to your car.
I’m wondering if it’s the brake switch causing it not to work.
http://www.austinthirdgen.org/mkport...se_control.jpg

 

I do have that schematic in my 88 elec diagnostic book. Apparently, according to the diagram, on the 88 TBI (165 ECM) there is no connection from the Cruise Control Module to the ECM? But on the 730 ECM the module is connected to C1 on the ECM. But I see no reference in the 92 diagram you sent to the ECM either. None of the conversion charts I found on ThirdGen for 165 to 730 address the cruise control. My second thought after the broken multi function switch was the brake switch but it seems to operate just fine. I'll check it again.

 

On the 165 I think the signal comes from a Vss buffer box.
The buffer on a 730 ecm is internal .
Being intermittent makes it hard to diagnose.

 

Was it working right before the swap? Did you check the vacuum lines to the CC in the front of the car? The brake light switch is the most common reason that CC doesn't work. Try adjusting it as maybe the brake lever is just barely touching it and if you hit the right bump it may engage/disengage all by itself since a command to set it may have been pushed during that ride?? Brake light switches are super picky and easy to cause to malfunction.