S-AFCII Help!

[RotaryDiagnostics]

I'd appreciate some assistance from the S-AFC users on the forum. This relates to an S-AFCII installed on an S5 turbo.

Question is: Do I need to rerun setup after momentarily disconnecting the S-AFCII power wire from the ECU?

Background: At the track last weekend I was having a rough running condition at idle and a minor miss at high rpm. The problem was undoubtedly related to A/F ratio since the tailpipes eventually became very sooty black. So troubleshooting the obvious possible culprits like TPS settings, vacuum leaks, plugs revealed nothing out of spec. Then I checked out the S-AFCII harness connections at the ECU for any problems. [It was installed by a previous owner.] In checking the splices, the power wire (red) pulled out of the quick splicer. Fixed that and the other splices checked out OK.

So when restarting the car it would barely run. No rpm readout on the controller and check engine lights for TPS and AFM. As a stopgap I removed the S-AFCII from the loop and it runs OK now, but I want to get the S-AFCII up and running again. All help appreciated.

[Phoenix7]

there are two ground wires in line and if one of them is not connected it will not run. Make sure it's grounded properly. Good luck.

[RotaryDiagnostics]

Yeah, I saw that the 2 ground wires were tapped into the same point on the ECU ground wire, so that may be an issue. I see from the wiring instructions that they should be tapped into the ground wire at 2 different distances from the ECU.

However, the car ran very well with it connected that way when I had it on the dyno earlier this year and it only started to go south lately. So I dunno, maybe it's time to get rid of the S-AFCII. Or maybe the car.

Thanks for your input.

[RETed]

Yep, I believe once the constant power is disconnected, it loses all it's settings.
Your experience seems to confirm that.
I don't have direct experience with the S-AFC II, but I did have a customer with an S-AFC I that had that problem due to bad install.


-Ted

[RotaryDiagnostics]

Mahalo Ted. Guess I'll be redoing the connections. As I'm sure you know, working on the ECU harness in the passenger footwell is not a very pleasant task. I assume the settings from the dyno run are gone also, so it will be back to the tuner shop.

Will running the car with the S-AFCII out of the loop result in a potentially harmful A/F mixture? The car has an upgraded RB, REV-II exhaust system and an HKS "intake". The turbo wastegate has been ported and boost is limited to around 7 psi. I'd like to run a few track events without the S-AFCII 'til I decide if I want to upgrade to a standalone. Think that's a problem?

[Phoenix7]

Well, if it's a stock turbo with stock fuel you should be ok without it, just don't drive it like you stole it.

The wastegate should still open around 6 or 7. Psi and as long as you don't go past 10 (ported wastegate will help) then the AFRs should be stock (slightly rich).

If you're ready for the standalone then go for it, otherwise stick with the SAFC. Also, take notes of the final tune so you can dial it in if this happens again.

[RotaryDiagnostics]

Good advice. Thanks! However, it's difficult to drive sensibly in track events. The other maniacs out there tend to tailgate alot.

Max boost I'm seeing in current ambient conditions is 7 psi. Stock turbo and stock fuel. Car runs OK when fully warmed up, but idle is still a bit rough. Gonna do some additional troubleshooting with the AFC disconnected before attempting to re-activate it.

[Phoenix7]

You still should be ok to mash around in a stock setup on the street but if it's for the track then you better take the car to your tuner and have him retune it....after it's re-installed properly.

TPS? Thermowax? vac leak somewhere in the intake path causing the rough idle?

[RotaryDiagnostics]

Originally Posted by Phoenix7

You still should be ok to mash around in a stock setup on the street but if it's for the track then you better take the car to your tuner and have him retune it....after it's re-installed properly.

TPS? Thermowax? vac leak somewhere in the intake path causing the rough idle?

Agreed on the retune.

Had a CEL for the TPS at an event in May and replaced it prior to this latest event with a new TPS ($$$). Checked voltages on the new TPS and set it using the 2-bulb method. Rechecked it since experiencing the latest problem and it was within spec. The accelerated warmup system has been completely removed including the thermowax (if that's the wax thingy you're referring to). Could be a vac leak but close inspection hasn't found one. I will do some spraying around with water mist to see if I missed one. Will also remove all the intake piping to inspect as well.

Car ran fine with the new TPS until I ran several sessions at VIR last weekend. Started idling rough after a couple of sessions and by the last session on Sunday, the idle was really rough and the engine was missing slightly at high throttle settings as well. Ya gotta love these cars.

[RotaryDiagnostics]

Well, here's the culprit causing the rough engine running. This hose connects the BAC valve to a port on the intercooler piping. Had to fabricate an adapter in order to pressurize the intake piping, but when I did the leak was obvious.

Now, I gotta redo the AFC wiring, do the setup and arrange another dyno session. It never ends.

[Phoenix7]

sweet, no expensive repair.