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Hey mate not too sure, I'll ask my tuner about this. Response, hope it answers your question The G4x plugin has 4 injector drivers So can run 4 coils as direct spark If you went wasted spark you need to pair two coils to the same driver which works fine... So in factory form you would wire two coils to the same driver for wasted spark config. But the link has 4 outputs so no reason not to do it direct

Was able to spend some time on the car the other day and narrowing it down to a wiring issue like you said Adam. It is certainly "a bad crimp, bad splice, loose terminal or terminal not latched" When I yank at the signal wires you can hear the idle drop. My Bosch 6 pin plug is also 1 out of the 2 connector clips so that could lead to a loose connection there too. All the scribbly bits is me pulling those wires and wiggling the connectors. But even when I'm not wiggling it its not a flat line for long.

I swapped out the GC8 engine bay harness for this. I tried not to shortcut anything because ironically I wanted to avoid the problem I'm having. Most of the connectors are new OEM, deutsch or better and wiring is all tefzel, heat shrunk in raychem. The bulkhead connector sits where the battery used to be near the washer bottle. When I first started trying to diagnose the issue (to help rule out the harness below) I wiggled/disconnected and visually inspected the wires in the engine bay and there was nothing showing up in logs. I didn't interrogate the wiring at the ECU, however, the DBW TB is now directly wired (wires going through the firewall to the passenger footwell to the ECU). I haven't attempted to back probe the TPS yet. If it was a 5V supply issue should the other sensors also be playing up? Seems only TPS Sub plays up. Note: Pictures below are before the ECU/harness was upgraded to accept DBW. Would it worthwhile opening up the ECU and checking the wiring here?

Yeah, wiring is all re-done with Tefzel, raychem heat shrink, wiring is shielded. I think the grounding in GC8s is just weak to begin with and the 8mm phenolic spacers must be messing with it. I'll update once I beef up the grounding, going to run the signal wiring ground to extra points.

IAT is normal. ECT also normal - around 80-90 degrees at most points At the point in the log where it begins to fault and deviate, I'm just gently accelerating up an incline, IAT at 30 degrees, no temp error codes or other errors showing in the log. There's no coolant hoses running to under the throttle body anymore. My next course of action is to run some extra grounds for the signal ground on the manifold and see if that improves things. Funnily enough, I changed to DBW because I was having idling problems with the standard IACV and TPS. It would randomly hunt at idle, but maybe this was a sign of bad grounding from the beginning since the DBW wiring basically repurposed those. My TPS Sub is AN Volt 4 (B136-21) at the ECU and is joined into one of the old iacv control wires. But now we've bypassed all the old iacv wiring and it's still acting up.

Quick Update, I think its going in the right track. I moved the signal ground from the back of the intake manifold to the middle as that was just the easiest to do without pulling off the intercooler etc. The bolt that came out seemed a bit corroded, so used a newer stainless bolt for the new spot. It drove better and for longer than it has in awhile, I threw in some short acceleration. TPS Main/Sub tracking closer than before for about 10 minutes, then TPS Sub started drifting again. Then at around 12 minutes it started getting worse and finally gave me a CEL Fault code 76 whilst going uphill. I started it up again and drove home with 1 stall. i 10 minutes seems be the magic number before things go awry. Will try to move the ground to the block on the weekend and see how we go. Log attached: PC Datalog - 2023-04-28 10;48;40 pm Different ground cleaner but 76 fault.llgx

Noted, will keep an eye on logs and won't even bother leaving the garage if the signal isn't perfectly married. Stalling in traffic is getting old. I see, so you essentially you skipped grounding it to the manifold at all and moved the grounds to the engine block itself? - Yep I have 8mm phenolic spacers (bolts aren't coated, just stainless), manifold is standard wrx but painted black, engine bay wiring harness isn't standard but all professionally done. I think I'll move the ECU/signal ground to the block and see what happens. We re-pinned it when changing to shielded wiring but I'll reinspect and do as you suggest... At this point any and all tips would help as the problem is intermittent but getting worse

Thanks Adam! Yeah it's strange it seems to only have sensor issues on the move and not when idling. Hard for me diagnose solo driving around trying not to stall/crash/watch the road/watch the multimeter lol (dont have long leads either). I'll clean up all the grounding points and beef up the grounding for manifold > block > heads as it seems to be a common Subaru issue to have bad grounds. Hopefully that at least it stops it from stalling/hitting limp mode but it looks like I'll probably need a touch up afterwards to make it run "like factory".

Copy of tune https://1drv.ms/u/s!AlUUjgUddC17gZ5zwoz850C9ybi9AA Log from day 1 https://1drv.ms/u/s!AlUUjgUddC17gZ5xQ51JQ_1s65LR7g Log from day 2 https://1drv.ms/u/s!AlUUjgUddC17gZ50_YdgPRWGmbuhMw Seperate log from day 2 https://1drv.ms/u/s!AlUUjgUddC17gZ51e2Y4IBiWpACBfw

Bit of an update: Still having the same issue even after trying out a new Bosch TB, installed 2 days ago. Wiring was changed previously, directly wiring the TB to the ECU, bypassing the factory harness. TPS Sub was still wondering, it's totally stumping me and the tuner. Day 1 post new TB: Car drove ok, albeit approaching red lights it would hold idle at 1400-1500rpm. It then stalled when I pulled over into a car park. Turned the car off for a few minutes, calibrated TPS and drove it home with same high idle issue. TPS Sub % consistently off by a few % from main. Day 2 post new TB: Calibrated TPS again, stored to ECU, the car started and idled. Drove out onto the road, approaching redlights it wants to stall, idle drops to 300rpm and alternator light starts coming on, I catch it by manually revving, I turn around to go home and every light im just manually holding the revs or slowly creeping with the car. Get back into my driveway and it now idles, but moving in and out of the driveway the idle wont catch. I'll post the logs and copy of tune when the forum stops blocking me.

Yeah I cant even reply to my own topic now with copies..

I now see what the gold standard is then, my TPS Sub and Main are drawn on by Michael J Fox it seems. I'll try some better grounding and do some more logs to see if it cleans up the signal.

So should there be nothing logged in TPS Error Accumulator if everything is working correctly? I'm guessing it may be a grounding issue due to phenolic manifold spacers, the ECU grounds off the top of the intake manifold.

Took some time to tackle this issue, bypassed the body/interior wiring harness altogether and directly wired the throttle body to the ECU with shielded wire. My battery has been relocated to the boot and the positive runs through the same hole as the engine harness so I'm thinking there might've been signal interference. Question: Should there be nothing in TPS Error Accumulator if everything is working fine? If so, then I'm thinking that maybe I have a grounding issue and signal interference? Copy of tune: 19.02.23 updated wiring.pclx Copy of log: PC Datalog - 2023-02-19 4;07;04 pm post wiring upgrade with some rev hang.llgx Drive notes: - Just cruised around and didn't notice anything strange aside from high idle/rev hang when at a stop, this happens frequently but will change from light to light. 850rpm at one and then 1500rpm at the next. - It looks like I was moments away from getting Fault code 76 again and then it came good...

Thanks Adam! Looks like I'll need to take it back to the tuner to diagnose then if its not something that can fixed tune wise.