99 WRX Idle Issues and stalling

[Adamw]

You will typically see small/short spikes of error accumulator during heavy foot work - maybe up to about 15, maybe 20 worst case and it should recover to zero within a 10th of a sec or so.  

Log I just pulled from my car below, the worst TP error spikes reach a count of 6.  You can see E-throttle target, TPS sub and TPS main barely deviate from each other at all, you cant even see the green or yellow TPS traces...

  

[koracing]

8 hours ago, Adamw said:

...you cant even see the green or yellow TPS traces...

 

show-off lol

[jqvp]

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.

[jqvp]

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.

[jqvp]

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

 

[Adamw]

Yep there is definitely still a significant variation between sub and main in that log.  I would say most likely it is some variation on the 5V supply or sensor ground as this is common to both sensors.  Since the sensor outputs work in opposite directions, if the supply voltage drops a little, one TPS reads higher and the other will read lower. 

The 5V output in the log shows spot on 5.00 the whole time.  If it were me, probably the next thing I would do is backprobe the 5V and gnd at the throttle body with a multimeter to confirm it is measuring a constant 5.00 there.  Preferably with some long leads so you can drive around a bit with the voltmeter connected.   

The stall is because the throttle position is reading wrong, the throttle blade will sometimes be more closed than what it should be.  For example in your 2nd log at time 4:30 the TP is at 2.8%, over the next few minutes of constant idle the TP drifts all the way to 4.4% to keep the RPM the same, then over the next few minutes it comes back down to 2.9%.  TPS sub does the exact opposite. 

[jqvp]

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".

[Adamw]

28 minutes ago, jqvp said:

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).

It definitely happens at idle - the pic in my post above shows 6 mins of sitting still idling with the TPS signals diverting away from each other then coming back.  

[Arktikpenguin]

For what it's worth, I chased grounding issues when I installed my billet RCM TGV Deletes and Corsa Veloce Billet Intake Manifold, even with the grounds going to sanded metal on the intake manifold itself. For the ECU ground (Driver side intake manifold) and Cam/Crank grounds (passenger side intake manifold), I ran those to 10mm bolts on the front side of the cylinder heads. On driver side, this is the dipstick bolt hole. On the passenger side, this sits right between the TGV and Coolant Crossover Pipe outlet to the Radiator. If you need pics, I'd be glad to grab them for you.

 

I have a relocated battery, so I have another ground wire running from the driver head to the ground that the battery normally goes to on the inner fender. I also have the Starter ground and Battery ground from the rear meet up here. On the passenger side, I just have a ground strap running from the cam/crank ground to the passenger inner fender where there is another body ground. To be fair, this may cause interference with cam and crank so I'm considering removing the extra strap here, but I haven't noticed any ill side effects.

[kaptainballistik]

May sound dumb.. but check the ECU PLUG side pin (if you are using the factory ECU plug) to make sure its "wiping" correctly on the ECU pin for the DBW or 5V Pin.

Drove me Sane..... 

Poked it with a pin so it wiped correctly and random stalling went away...

 

[jqvp]

23 hours ago, Adamw said:

It definitely happens at idle - the pic in my post above shows 6 mins of sitting still idling with the TPS signals diverting away from each other then coming back.  

 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.

8 hours ago, Arktikpenguin said:

For what it's worth, I chased grounding issues when I installed my billet RCM TGV Deletes and Corsa Veloce Billet Intake Manifold, even with the grounds going to sanded metal on the intake manifold itself. For the ECU ground (Driver side intake manifold) and Cam/Crank grounds (passenger side intake manifold), I ran those to 10mm bolts on the front side of the cylinder heads. On driver side, this is the dipstick bolt hole. On the passenger side, this sits right between the TGV and Coolant Crossover Pipe outlet to the Radiator. If you need pics, I'd be glad to grab them for you.

 

I have a relocated battery, so I have another ground wire running from the driver head to the ground that the battery normally goes to on the inner fender. I also have the Starter ground and Battery ground from the rear meet up here. On the passenger side, I just have a ground strap running from the cam/crank ground to the passenger inner fender where there is another body ground. To be fair, this may cause interference with cam and crank so I'm considering removing the extra strap here, but I haven't noticed any ill side effects.

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. 

4 minutes ago, kaptainballistik said:

May sound dumb.. but check the ECU PLUG side pin (if you are using the factory ECU plug) to make sure its "wiping" correctly on the ECU pin for the DBW or 5V Pin.

Drove me Sane..... 

Poked it with a pin so it wiped correctly and random stalling went away...

 

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

[jqvp]

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

[kaptainballistik]

Hmm, Are you running the water heater pipes to the Throttle body, and is there any DBW temp error codes being thrown?

And what's your intake air temp doing at the same time?

(Work computer, cant open logs!!)

[k4nnon]

Hey, just to post on this, it may have already been covered but i didnt read every reply, just skimmed. The iac valves are known to stick, They can be taken apart and cleaned and sometimes a cleaning will fix some idle issues. If you havent physically taken it apart to look at it and see if its clean or not maybe just do a quick look and see how it looks. Hope you get it fixed up!

[koracing]

2 hours ago, k4nnon said:

Hey, just to post on this, it may have already been covered but i didnt read every reply, just skimmed. The iac valves are known to stick, They can be taken apart and cleaned and sometimes a cleaning will fix some idle issues. If you havent physically taken it apart to look at it and see if its clean or not maybe just do a quick look and see how it looks. Hope you get it fixed up!

The subject vehicle here is using a DBW throttle body for idle control so a sticky IAC is unlikely the culprit.

[jqvp]

19 hours ago, kaptainballistik said:

Hmm, Are you running the water heater pipes to the Throttle body, and is there any DBW temp error codes being thrown?

And what's your intake air temp doing at the same time?

(Work computer, cant open logs!!)

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.

 

6 hours ago, k4nnon said:

Hey, just to post on this, it may have already been covered but i didnt read every reply, just skimmed. The iac valves are known to stick, They can be taken apart and cleaned and sometimes a cleaning will fix some idle issues. If you havent physically taken it apart to look at it and see if its clean or not maybe Fjust do a quick look and see how it looks. Hope you get it fixed up!

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.

[semih]

i wonder did you use shielded cable for that wiring? or i wonder if it's helps? (same car here)

if i were you i would redo whole ground wiring on that car

[jqvp]

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.

[Adamw]

Do the GC8's have a large multipin connector in the engine bay near the firewall where the cabin loom attaches to the engine loom like the later subarus do?  The later ones (and toyota 86's which use the same connector) are fairly well known for the terminals in those connectors losing spring tension and making poor contact.  This is really what yours looks like to me, a poor connection in the 5V or sensor ground between ECU and TPS.  Engine grounds shouldn't really matter provided the TPS is connected directly to the ecu.  Have you tried measuring the voltage at the TPS as suggested earlier?

[dx4picco]

no plugs close to the firewall. all shielded trigers go around the right leg of the chassis, and the rest (power and signals, included tps) go through the two square plugs located behind the battery on the left side. 

[jqvp]

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?

[kaptainballistik]

16 hours ago, Adamw said:

Do the GC8's have a large multipin connector in the engine bay near the firewall where the cabin loom attaches to the engine loom like the later subarus do?  The later ones (and toyota 86's which use the same connector) are fairly well known for the terminals in those connectors losing spring tension and making poor contact.  This is really what yours looks like to me, a poor connection in the 5V or sensor ground between ECU and TPS.  Engine grounds shouldn't really matter provided the TPS is connected directly to the ecu.  Have you tried measuring the voltage at the TPS as suggested earlier?

You may have just solved an issue with my BRZ.... 

[Adamw]

13 hours ago, jqvp said:

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.

It is not only the TP sub.  The ECU always uses TP main as the control variable so that will always stays close to target which may make it look like it is only a TP sub-issue. You can see in my April 26 post above the engine is idling at a steady RPM and ign timing is stable (indicating the load and/or throttle is not moving much), yet the TP main drifts up then back down, while the TP sub drifts down then back up - so most likely neither is correct.  The signal output is opposite from the main Vs sub, and the output of TPS sensors is "ratiometric" (proportional to supply voltage), so a change in supply voltage will make one read higher and one read lower.   The voltage at the sensor should be the first thing to confirm.  If you find that not always within about 5.00+/-0.01V then work your way backwards from there, most commonly a bad crimp, bad splice, loose terminal or terminal not latched into the housing properly.  The 2% change in main Vs sub that is in the April 26 pic would only require about a 0.04V change in supply voltage.  

[jqvp]

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.

[Intrexin]

jqvp. Reading through I was thinking grounds but as soon as I saw the 8 mm phenolic spacers yeah I totally think grounds are a part of the problem. In a Subie, the ECU grounds are from the intake manifold. So that's all your 5volt grounds like sensors. The spacers make it a much worse ground esp if you have coated bolts. Look at iwires grounding kit video, the way they do it ties the engine and intake mani together to get around the grounds with spacers issue. Should be easy to test if I'm right, just quick pop a ground from the intake manifold to the engine/chassis ground. I go agree yanking on that connector prolly isn't a good thing either, but if it still does your issue when that connection is good than that's more a different problem.