Alright, 3 issues here.

Offender = '87 GXL

1. I'll start with the ACV. Upon deceleration, the car cuts out, it sounds like it just stops supplying fuel, and with maybe 5% throttle, it sputters like a ****. I unplugged the ACV green electronic connector and while just sitting in my garage, revving, it appeared to fix it. I'm thinking I'll just buy a god damned ACV blockoff plate and remove that air pump that I've been wanting to for so long.
2. Second, my TPS is bad, or at least I think it is. I have a consistent hunting idle. In the range of 1400rpm to 1600rpm. Cold, hot, in between, always. It'll hunt steadily between that range. The TPS IS adjusted properly. I unplugged the TPS, and the hunting stopped. I assume I'll need to source a new one. Is this a correct assumption?
3. My 5/6th ports do not work. I have no mufflers. The exhaust system is as follows: Headers -> Pre Cat -> Main Cat -> Y-Pipe -> Straight out to duals. My guess was that the aux ports aren't actuating because of not enough velocity, but even though I don't have the stock mufflers, I'm positive my exhaust size is the same, this would in fact mean that something else is wrong. I assume that once I block off my ACV and split air pipe, I can gut my cat and call it a day? (I did spray penetrating oil and manually work the actuators. They do move, it takes a bit of work but they go all the way down and up again..)

I'm not super worried about the 6PI anyway, as I'm starting to gather what I need for an NA-T. Besides, removing the air pump, blocking off ACV, and the split air pipe wouldn't affect these ports on an S4 NA even if they did work, amirite?

To recap, is there anything wrong with:

1. New TPS
2. Blockoff ACV and split air pipe
3. Gut what's left of my cats

Thanks!

 

1. The green ACV plug? You mean the O2 sensor? It's a green plug with 1 black wire on my '88. If that's the case, you might want to replace the O2 sensor.

2. Test the resistance values across the spectrum for the TPS and make sure it's set to 1 volt at idle (at operating temp, not cold). If it tests bad, replace it.

3. First of all, no you can't remove the split air pipe on a S4 and expect the ports to open. The pressure that activates them is supplied by the split air pipe. The little vac line tee'd into it feeds them.

If it's hooked up correctly, and the ports still won't open, you can try adding a bend where the split air pipe connects to the main cat (on the split air pipe). Racingbeat's presilencer uses this method to help build pressure in the pipe. Take a look on their site and you'll see what I mean.

You should also make sure the aux port actuators move freely and that the vac line that supplies pressure it's falling apart due to exhaust heat.

 

Green Plug: I'm not sure what it is. If it's the O2 sensor, then how does removing the ACV and replacing it with a blockoff plate work? Where does the O2 sensor sit then?

TPS: It's bad, pretty erratic throughout the range. I'll start sourcing a new one.

6PI: Like I said, I'm not worried about them at all, I'm going forced induction in the spring. I know the ports don't work now, and I know they won't work afterwards. I'm more interested in making room in my engine bay. The aux ports won't matter anyway with a stock S5 turbo, I'm going to remove the sleeves entirely. One thing I *might* try if i get bored is your suggestion on the bend in the split air pipe. Since I'm gutting the cats anyway. I don't even know if it's worth trying over, since I don't expect to be high-revving in the winter, but it would be nice. I'd prefer no air pump and no ACV over busting nuts trying to get said ports to function.

My primary concern is what else can I break?

 

The green O2 sensor plug (harness side) comes out from under the intake manifold and plugs into the O2 sensor, which is screwed into the exhaust manifold. It's not related to the ACV.

The ACV has 2 solenoids; each with 2 wires. These are the only electronic connections on it, so if the plug you're looking at has only 1 wire, it's the O2 sensor.

 

Ah, alright. I'm at work, I'll look at it at 5 and post more then.

 

Not the green plug, I looked at it, it's the blue plug, towards the front of the ACV.

 

And I was wrong the entire time, it's not the ACV, it's the Bypass Air Control Valve, or so says the FSM.

The plot thickens?

 

Also, I've noticed that I do not have an air bypass relay.

 

Well, the BAC does very little. It allows additional air to bypass the throttle plates during the first 17 seconds after startup (along with the AWS). And then it also supplies air when the power steering is engaged. Not sure why you saw a positive result by unplugging it.

In my experience, changing out the TPS has helped smooth out the engine during decel. The ECU does actually cut fuel to 1 or both rotors during decel. By about 1400 RPM (ala Hailers) fuel is switched back on so the motor can idle. If your TPS is bad, then the ECU is not triggering these event properly.

 

It's useless anyway. The BAC alone will supply enough air to reach 3000 rpm at startup. Unplugging / removing the air bypass solenoid will reduce the warmup idle by maybe 200 rpm. I don't use one.

 

Alrighty then, A TPS alone should fix these problems.