Curious if anyone had thoughts on my issue listed below. I am re-installing stock ECU and downpipe in an effort to pass CA smog.

Issue:
-Repeated beeping (can't honestly tell if there is a pattern) and gibberish from the odometer after installing stock ECU in place of PowerFC and re-installing stock downpipe in place of HKS downpipe
*See Video*

-Overall very rough idle, oscillates between unknown RPMs (tachometer broken, no access to RPM reading on FC commander with stock ECU)
-Lots of smoke from rear
-NO CEL

*Note*: SRS light IS on, I assume due to installation of Worksbell hub and QD for aftermarket steering wheel (no airbag). I read that stock ECU will beep 5 times for SRS but did not notice that pattern in my recording.

Background:
'94 touring rebuilt around 100 miles ago
BNR stage 3 installed recently

Before re-install of stock components; behavior and "symptoms":
PowerFC base map
HKS DP

No beeping and idle would eventually even out around 850 RPM. Car seemed to be running relatively well on the PowerFC. Gauge is still mainly broken (SRS light on, no readings from odometer, no tach or speedo readings) but the odometer does not blink in the crazy pattern seen in the video.

Thanks in advance

 

Beeping is the airbag computer. If you have removed the airbag the computer is gonna be mad about it. The computer is up under the dash on the driver's side of the transmission tunnel, that is probably what's beeping.

Surging idle may be from the throttle body adjustments that is typically made when you install a PFC. Or it could also be from the 4 wires that are cut/removed when you install a PFC, those are inputs to the ECU that can affect idle.

The cluster just sounds like the cluster acting up, they all start to do weird stuff as time goes on. I doubt that's related to the ECU swap.

Dale

 

zli944,

Regarding the odometer, you should remove and inspect the speedometer for some bad components. Dependent upon how long this problem exists may determine how much damage to the board has occurred. Search for Troubleshooting the FD Speedometer and just got done fixing FD speedometer for more information about it.

If you swapped to the original ECU, did you reconnect all wires to the harness? I am not "smart" on PwerFC vs OEM ECUs. I've heard of a poorly grounded PowerFC cause wacky things on the instrument cluster. I defer all questions about the PowerFC to DaleClark. He IS the RX-7 Guru!

As a positive note, I saw your Low Fuel Lamp on in the video. I haven't seen mine do that...ever!

 

Gen2n3,

Thanks for the tips! I did follow Dales writeup and spliced the 4 wires with QD connectors but I think I have to take a look at them again, AWS is one of those wires and my car did not rev up to 3K on cold start.

You bring up a pretty good point with the grounding. There’s a black connector near the ECU that’s been disconnected this entire time... I’m having a tough time finding the exact connections of all the wires near the ECU. Off the top of my head, 2 ring ground wires (I have both just between the chassis and the ECU) and that one black connector.

The low fuel light might be due to a couple issues. I replaced all the bulbs with LEDs in the cluster (very much regret it because I think that’s what caused some issues with the cluster in the first, forgot the first rule; if it ain’t broke, don’t fix it) so maybe it’s a resistance thing or just leakage from an adjacent light.

edit: oh haha, you were saying the low fuel light is a positive. I’ve got half a tank left and the lights on! It’s always on, so it’s broken in the opposite way

Anyway, appreciate your input.

 

zli944,

Thanks for the feedback. Especially about the Fuel Lamp. It made me chuckle - "broken in the opposite way."

One could say that I am the curator of the speedometer/odometer blank out threads. You are welcomed to add to that conversation when the time is right.

Based upon my observation, the AWS can be easily defeated when starting the car. Simply pressing the brake pedal in A/T cars or starting a M/T car in false neutral typically bypasses the AWS.

Please let us know what you find when peeling back the onion of spliced wires.

 

The ring terminals by the ECU just need to bolt to a ground. The stock ECU has a stud on its bracket that they bolt to. You can also just use one of the bolts that holds the ECU to the frame as a ground.

I'm not sure what happens if those grounds aren't connected, but it's a good idea to have them connected.

Dale