Proper PowerFC ECU grounding and mystery black connector near the ECU
 

'94 Touring
PowerFC

PowerFC:

The PowerFC is bought second hand and I noticed it had the mounting tabs that are present on the stock ECU velcroed onto the PowerFC. In terms of connections, it is only connected to the car via the 4 yellow connectors (B1-01s).
There are only two ground wires around there (one for the fan recall I think and another from an unknown source). I have those two rings grounds connected to chassis via the mounting tabs and a bolt but again, the tabs themselves are only velcroed to the PowerFC.

Is there a separate ground for the PowerFC? Is the velcro the correct installation method?

The issue I am troubleshooting is that the car will stall and cut off as even when I slowly decelerate. I am going to check the dashpot, IAC and what the clutch sw reads from the PFC but the PFC mounting and grounding has always bothered me....


Mystery connector:

Does anyone know what the connector circled is? From my research, I think Dale mentioned it's a test connector for the Fan recall but just wanted to confirm. The loom it's coming from does go to the fan recall black box.

https://cimg1.ibsrv.net/gimg/www.rx7...ecd8b6f8c2.png

Yep, that's the fan recall test connector.

The body of the PFC does NOT need to be grounded. I've driven cars with it laying on the carpet in the floorboard and the car ran fine.

The 2 ground wires (one for fan recall harness, one for ECU harness) do need to be grounded to the frame.

Did you do the full install process - remove/cut the 4 wires, etc.? It's in the PowerFC FAQ I wrote a zillion years ago.

Did the car run fine on the stock ECU?

Dale

>Dale

Great, good to know that the PFC is hooked up correctly. The two wires are grounded to the frame so I guess I'm fine grounding wise.

Your PowerFC FAQ is what I tried to follow when I installed it, I have those 4 wires with quick disconnects and ran through the idle learning procedures without any problems (it seemed).

I last put in the stock ECU and it was beeping (you replied to my thread here: Other cluster issue thread) and generally seemed to be running very rough though it did not suffer from the random stalling when coming to a stop but I only drove it around 2 miles to get it to a garage for storage. I think the quick disconnects on my wires might have come undone on at least one so that may explain the issues when running on the stock ECU.

But overall, I think I can dismiss ECU grounding and wiring as a possible culprit for the random stalling. I'm going to take a look at the dashpot, IAC and clutch switch next and then onto fuel pump voltages. It does very much seem like it's an electrical issue in someway.

A random follow up question:

Is the BAC and IAC the same valve on the back of the UIM? In the FSM, I only see the IAC listed with testing procedures but I do not see a BAC. Are they the same? Or is it a nomenclature thing.

Nomenclature. Really, on the FD, it's called the ISC, Idle Speed Control. The FC's valve was the BAC - Bypass Air Control.

The ISC is on the firewall side of the intake manifold. It can be removed without removing the UIM, but if you still have the AWS system the hoses many times are in the way and may make it tricker.

I would also check your clutch switch, that should be an easy check in the Sensor Check screen on the PFC Commander. A bad clutch switch can cause stalling when returning to idle. Past that, clean the ISC and make sure your dashpot is working and adjusted properly.

Dale