I've exhausted all my thoughts except swapping in Andre's speedometer. I tried grounding the Tach and using the OEM coil trigger wires to run the car and neither had any effect.

While I was running the car I decided I should check that my TPS was in spec because of some idle hunt issues. Measured between the top pin(sensor Ground) and the bottom pin(full range). with the throttle closed I measure 4.5V, fully open I read .9V. So based on the FSM the TPS is out of spec and backwards? I'm not sure how that would happen since this is wired as if it were stock. Maybe its just how I'm measuring it, by probing the pins. I only did this once before and it was using the FC commander.

 

Victory and then defeat. I took care of the TPS issue, that was just a matter of where I was measuring from. I then switched my throttle and TPS over to another unit that ran on the car when it was stock. This eliminated any throttle adjustment issues that may have been causing any idle issues and light throttle. I also switched my coil triggers to route back through my engine harness as before. I also put in the cluster I had laying around from my old car.

Then came time to start the car. Car fired without issue and idled rock solid. Idle was low for a cold start but I expected some bypass screw adjustment. Best of all the speedometer and ECU were not reading any speed!! The car got warmer and I gave it some throttle input to see how the car and RPM/speedo would react. Revved smoothly held RPM well and responded well with not Speed showing up. Then when I wanted to bring it back to idle it went too low and died.

I cleared the car out and restarted. Speedometer still read correctly but the odometer was not displaying. Some seconds later and the odometer came back, and the speedometer began its BS again. at this point I have to say it is a car issue rather than a speedometer issue. I hope I'm not frying speedometers trying to track this issue down. I'm less concerned about the mileage racking up at this point and more concerned about any tuning issues that this may be causing because it seemed as though the speedometer and idle surge issues coincide.

 

Another update. I disconnected the Tach signal wire from the ecu and the problem went away with the speedometer working as normal. This prompted me to make my own tach signal wire to bypass the OEM wire. Problem comes back when this is connected. In my mind this narrows it down to two things.
1.) Both of my clusters are bad.
2.) Something inside the ECU is causing this(highly unlikely for a new Adaptronic PNP and I would think the issue would occur without any wire hooked up)

Does anyone have any other suggestions to the cause of this?

 

When you are having the malfunction, you are also seeing the speed measuring at the ecu? If so, I didn't catch this before. The speed signal is sent from the cluster, to the ecu. So this would mean that the speedo is really convinced that there is speed signal present. But the problem definitely goes away, when you remove the tach input from the cluster?
I'm scouring the wiring diagrams to see if I can pinpoint another area to check. I'd be more likely to blame some potential re-wiring issue than to blame TWO clusters with the exact same problem.
It might have been some type of ground that you simplified or relocated because it made sense to you, but they had designed it only to work the way they wanted. If that makes any sense ??
I'm going to keep looking and brainstorming.

 

The ground for the cluster, goes thru the connector x-14 which connects to the engine harness you re-did. I checked the diagrams you sent me in PDF. I don't see the connection you made to ground on the engine harness. The end point of the ground is at the number "3" in this image.




Looks like somewhere in the rats nest or by the injectors.

Did you add this ground when you built the harness?

 

Andre, the malfunction is appearing on the ECU as well as the gauge. As you suggested, the grounding can still be the root cause of this. The diagram I sent you doesn't show any of my routings for the grounds, pin 4A, 4B, 4C, 5N. I can assure you that they are done though. The cluster ground passes through X-14 on pin 5N and is grounded to the engine on the rear most stud of the UIM/LIM joint. The questionable part of this is whether or not this ground should be interconnected in the harness to the grounds coming from the ECU at pins 4A, 4B, & 4C. Checking my intact stock harness the answer would be yes. Whether this should be the case with the aftermarket harness is questionable. The thing with grounds though is that they are all connected through "ground" anyway.

One wildcard here with grounds could be my ignition coil grounds. I'm running IGN-1As mounted in the AC pump location. The instructions for these coils are to ground 3 of the 5 pins.
-One goes to battery ground (in my case, chassis since my battery is in the trunk)
-One goes to rotor housings
-One goes to sensor ground (pin 4D)

Perhaps these coils are feeding some sort of pulse through ground up to the only other gauge, the speedo, that could display such a signal. Thoughts?

 

For what it's worth, ecu pin 4C grounds at the same location as the cluster ground on the engine, but I think you're right and it shouldn't matter.
What does concern me is the ground setup for your coils. Based on my research, I was under the impression that all the grounds should be joined and ground to the housings.
The multiple ground wires are meant really for other types of oem applications where the wires are used for misfire and power detection.

 

Maybe this is my root cause, but I'm going to expect the worst and celebrate a win if i works, (this problem is beating my problem solving skills and spirit to death). I got the IGN-1A wiring diagram from here, Adaptronic 440 Select ECU Series 4/5 Rx7 w/ Direct Fire IGN-1A Coil, no a/c & PS, and I believe I confirmed this with IRP or CLudwig but maybe, just maybe it will alleviate the issue If I am to tie the grounds together. Off to the garage.

The good news is with my tach disconnected I'm not racking up mileage and giving the ECU a false speed so I am confident in driving the car. Just have to adjust some settings to where I can get it to restart without throttle input.

 

Did you ever take another shot at this, or does winter have you down for the count?

 

after reading through this i really want to know what happened. its like a troubleshooting cliffhanger...

o_0

 

Sorry for the cliffhanger, winter has the car down and I've been rebuilding my Subaru daily. I purchased some high quality shielded 2 and 4 wire lengths. I have the harness out and will be replacing my CAS signal wires as well as removing the coil triggers from the engine harness. I'm going to route the coil triggers like any sane person would've from the start and patch into the stock igniter connector. Hopefully this solves everything. I'll keep progress updated when progress occurs.

 

I am very curious if you find a solution for this, my car sat over winter for a few months on a battery charger and when I got it out of storage the same issue you are having started. It began with the odometer digits going out intermittently and now the speedometer sits at about 25kph when stopped. As I slow down it almost reaches zero then once stopped it creeps back up. I will see if it follows the tach next time I take it out. I feel it is most likely a ground issue of some kind or a rodent chewing on wires.

 

Finally got the car back together again. I went back through my engine harness and replaced the CAS trigger wires with a higher quality shielded wire. I also removed the coil trigger wires from the engine harness and went back to using the stock wiring for the coils. For this I made an ignition harness similar to the Sakebomb kit. Got the car started and the speedometer issue is still there, at least until the car reaches about 160 degrees where it bounced its way down to zero.

I still have reason to believe that this is being caused by my home built wiring harness/harnesses. While they are high quality I may be missing something internally. One thing that leads me to this conclusion is that while looking at my logs, I see some funny things going on with the crank timing intervals even after fixing the harnesses. Time between the missing tooth on the FFE wheel should be 2.5-3x that of the time between normal teeth. I am getting almost exactly 2x which is too little.

My other theory is this is all something to do with my engine. This engine was rebuilt and running on a PFC in my old car and showed similar erratic idle and dying issues as well as speedometer problems. I don't believe there could be something wrong with an engine to cause this but if I am to replace my engine harnesses with Rywire and Sakebomb units and the problem persists, the only variables I see being suspect, because they're from my old car, would be the block and intake manifolds.

Thoughts?

 

Update:

Timing issue has been resolved through work with Adaptronic and it is/was not the cause of the speedometer issue.

I replaced the wires in the harness that carry the speed sensor signal with shielded wires and grounded the shielding both in the cabin and under the car. This seems to have 90% of my issue. The speedometer now rarely shows signs of reading while the car isn't moving and this only happens about once for a few seconds after it starts and won't happen again while the car is running. So it seems this issue is strictly interference based. For me it's most likely caused by my home built wiring harness, not braiding certain wires or another trick that aftermarkets and OEMs use that I'm not aware of. For others with the same issue I would guess its from a degrading stock harness that is crispy and broken.