Stumbling idle. AAC valve?

[gtrjon]

So I've spent an hour searching and haven't really found much. Basically when the car is out of gear or idling it will drop to 200-400 rpm for about 5 seconds then it will pick itself up to where it should be around 1000rpm. It doesn't always pick itself up tho sometimes it stalls out. Does this sound like a faulty aac? It does it hot cold whenever. Not mafs as I am running a vipec. My tuner seems to think its an AAC. Any ideas?

[bobbo]

What happens if you turn the AC on?

[gtrjon]

Ac has been removed. From the more research I'm doing I'm shying away from it being the AAC valve since it has the same problem on a cold start up or with all the accessories on or off it makes no difference

[bobbo]

What does your a/f do? What are your o2 sensors showing for values?

[gtrjon]

sorry should of specified. idle is normal around 12.5: when it stumbles it leans out to 13.5:1-14.0:1 then when it recovers its back to 12.5:1. o2s are irrelevant as i am not running any, not necessary with my vipec

[bobbo]

That's an awful thirsty idle. What's your ecu demanding for a/f at idle?

[Skym]

Sounds like TPS is on the way out or misadjusted (age related failure with TPS). When misadjusted the TPS doesn't touch idle contact. When it touches idle contact inside TPS, ECU switches to kick down tables which kick rpm up to prevent engine stalling or dropping below idle rpm if engine has load on it (head light's, aircon, going up a hill, etc).

R32 still has idle contact's inside TPS that can bend over time, on Series 2 R33 TPS they switched to voltage based idle, WOT contact's (removed the idle contact's).

If want another option with TPS, can use fly by wire setup (Motec M600 + aftermarket TPS) to eliminate the troublesome stock TPS. Not sure if ViPEC can run fly by wire.

[gtrjon]

tps is within spec according to readings on vipec. could the vipec read the tps as being within spec when in fact its not actually touching the idle contacts?

[h4X6]

It's possible. Check tps at the sensor to double check. And wow man does your car idle rich...

Sent from my Z10 using Tapatalk 4

[gtrjon]

with large pro cams (270 duration 10.25 lift) not drop in pon cams it takes a bit of fuel to idle hence the richness. now back to the problem tps is within spec both at the harness and on the vipec

[h4X6]

Hmm maybe a small leak somewhere? All gaskets good? Clamps. Etc. Just throwing out random ideas at this point.

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[Skym]

tps is within spec according to readings on vipec. could the vipec read the tps as being within spec when in fact its not actually touching the idle contacts?

Sometimes TPS is within spec but has failed. TPS on my car didn't pop up a TPS error code on ECU (voltages looked ok from TPS plug), but could wiggle TPS plug, engine stumbled, wiggled it more and engine stalled. Replaced TPS (also had a faulty o2 sensor at same time which might have played a part), problem solved. Sometimes it's wiring to TPS plug and shows up when hit a bump in the road.

with large pro cams (270 duration 10.25 lift) not drop in pon cams it takes a bit of fuel to idle hence the richness. now back to the problem tps is within spec both at the harness and on the vipec

Did you raise the idle rpm to suit the more agressive cams??? You said it idles around 1000rpm, when it needs to be at 1200rpm for 270 duration cams.

Tomei mention idle rpm, A/F ratio (I assume at idle) for those spec cams here -

http://www.tomei-p.co.jp/_2003web-catalogue/e140-157_reytec_page/e154-157_te-info.html

[gtrjon]

when is said 1000rpm i meant closer to 1100-1200. its not something regarding my set up since it idled fine before. Tomorrow i am going to pull aac and iacv and clean and replace to see what happens

[Skym]

Oh, ok.

Sometimes idle valves get dried oil build up due to turbo oil seal failure (turbo failure), oil in blowby (catch can should stop this from happening), etc, so doesn't harm to clean them.

[bobbo]

I wouldn't go to the trouble of pulling the IACV. I don't mean to offend if you already know but all it does is open an air passage to increase idle when cold. Voltage is applied and a coil SLOWLY shuts it. If you had idle problem caused by your IACV it would be more consistant and only when cold.
With experience I've accumulated trouble shooting my own idle issue your symptoms don't fit IACV problems. AAC... possibly as it's a solonoid. Easier to trouble shoot by simply unplugging it and see what happens.
Best of luck Jon. Idle issues can be a PITA.