CTS sensor at 170 degrees is 336 ohms at the ECU. Seems to match values I can find online. At 170 deg the AAV is closed. Should check to see how much air its still getting through there.

Not really sure what else happened. I tested another AAV I have to see if it behaved similarly and started thinking about the idle control valve (I don't recall what it is actually called on an S3, its some sort of vacuum bypass). While I was trying to decide if I should take that apart again, I decided to adjust the idle. Well, this time it worked.

Before I moved this idle adjust screw both ways with no luck. Had it further in when I cleaned the valve with no difference, so I backed it out to where it was just to have things as they were. I could tell where this was based on the dirty threads.

So I'm not exactly sure what happened, but it will now idle lower. Now I have to deal with a rough idle, which I was expecting before with the dirty fuel tanks.

 

I recall it simply being called the "idle air adjustment" or "idle speed adjustment"

It (and the AAV) simply take metered air and bypass it around the throttle blade. They're effective only when the throttle is closed. Once the throttle is opened the incoming air is greater than the bypass air.


There's no arguing with success



How rough is 'rough'? A tiny tremble is pretty much the norm on these engines; glass smooth is a holy grail type of thing.

Cheers
DD

 

Yeah maybe I am ruined on the 5.3? Rough is I can visibly seem the engine hiccup every few seconds at idle and though it sustains revs okay, it initially stumbles a bit on acceleration. Also seems to dip from 800 down to 600 in gear, which seems excessive.

Pressure varies, initially its a good 36 psi, but after running a bit it seems crud gets pulled into the filters and it can drop to 25-30 psi. I would leave the key in with the AFM open to just circulate fuel through the filters but the noise from the regulator is reduced after a minute or so, and I'm not sure how much is actually getting pushed through.


Any thoughts on unplugging the ECU? How analog is this thing? It's one of the only things I can think of as far as the idle adjustment suddenly working. As I said before, I unplugged it to check the CTS signal.