help! hunting on idle when in park

[lucasryanmartin]

So my04 GT auto, vehicle will start and run fine when under open loop operation, but once it warms up and almost instantly when the ecu switches to closed loop, it starts to hunt. With a/c on and off makes no difference, but only happens when in park. I'm not to familiar with subaru's, but how is the idle controlled? Electronically or via am IAC valve? Off the top of your heads does anyone know of what could be the root of my issue? I ran upper cylinder cleaner through her about a month ago and a few days later i could've sworn it felt like the throttle butterfly way sticking a little on deacceleration, but it hasnt happened since. I know its a possibility for the cleaner to seep through into the motor and pcb on the side of the throttle body, is this a common occuranance for subaru's? I'm also a little keen to think it may be the afm playing up, but i dont want to just throw money at it.

Many thanks in advance!

[bigBADbenny]

https://www.google.com.au/search?q=site ... fiqCJq5XeA


https://www.google.com.au/search?q=suba ... ark+-rough

[bigBADbenny]

Don't throw money at it.
Throw your brain at it.

If you didn't follow the rec UEC procedure (pretune link below) then do it again.

Just a minute of ggling told me front O2 sensor, avcs, injectors plugs coil packs are the most likely contenders, but I'd devote more time for research if my car my money.

Spend the savings on a Tactrix

[lucasryanmartin]

Hmm ive got no mods, considering it only happens in park then i'm fairly certain its not avcs as my car isnt that cool, nor is it coils or injectors as it doesnt happen under any load, and or when accelerating or deaccelerating. What problems have people had with throttle bodies? I know that the maf has a lot of issues being dirty seeing as they are a hotwire type, what sort of cleaners have you had success with or recomend?

Cheers.

P.S i looked at your links but i couldnt find anything specific to my issue.

[bigBADbenny]

A lot of assumptions going on there.
You are not looking hard enough.
Not my links, I'm just googling your issue.

Avcs? You have both inlet and exhaust avcs...
But my guess is the O2 sensor being likely.

My advice, save up for a tune and get the tuner to do diagnostic logging before proceeding
That's if you cbf'd logging it yourself or getting help from a local member.

You'd be throwing good money at it at least...

[bigBADbenny]

viewtopic.php?f=56&t=20196
This post describe MAF clean and correct UEC procedure.

Rough idle/O2 sensor
https://www.google.com.au/search?biw=32 ... rough+idle

Rough idle/avcs
https://www.google.com.au/search?biw=32 ... +idle+avcs

Diagnostic for avcs is to log all VVT angles idle & 1500 rpm and at freeway cruise speed.
And I'm just googling the diagnostic procedure for the O2 sensor cos I'm curious.

http://m.autoserviceprofessional.com/ar ... -diagnosis
This is great and will give perspective to the procedure described in the FSM

[lucasryanmartin]

These motors have variable valve time? Wasn't aware of that.
The thing is hunting but, its not like a rough idle, it will only occur when idling in upark, and wont play up in neutral.

back to avcs, its oil pressure operated effectively, with ecu controlled valves that adjust the hyrdaulic pressue...there is a possibility of that on idle these avcs valves might be staying on, slightly causing one, most probably the exhaust cam to stay even the smallest amount rotated, causing a lower vacuum effect or increased egr effect which could be choking the engine a little which would make the revs drop off then the o2 sensor sends a low voltage signal to the ecu so it adds fuel and revs pickup again...will use a scantool at work tomorrow to see what info i can gather about the avcs, do you know were itd be best to find specified results for this?

I appreciate your help mate!

[lucasryanmartin]

Sorry that should say that the o2 sensor would send a high mv signal to the ecu so it would lean the mixture a bit causing revs to pick up again

[Sean82]

on idle, cams should be advanced/retarded 0*.
I had a massively lumpy idle a while back (before engine swap) and it turns out one of my intake cams was stuck at ~40* advanced.

It's odd that your engine is hunting in "PARK" only and not N also.

Have you noticed an increase in fuel consumption at all?

[lucasryanmartin]

Yeah, no matter what it wont play up anywhere else but park.

When i got the car 5 months ago i notoced how poor the fuel economy was, but in the last few weeks its gotten better, but im thinking thats due to upper cylinder cleaner

[bigBADbenny]

The procedure is described in the FSM
Get yours here:
viewtopic.php?f=10&t=26203

[bigBADbenny]

So I googled the difference between P and N in an auto:

"p" or park is the same as neutral but with the locking pin that stops the output shaft to stop the car from rolling.

It might be worth googling issues related to the neutral position sensor etc

[Sean82]

So I googled the difference between P and N in an auto:

"p" or park is the same as neutral but with the locking pin that stops the output shaft to stop the car from rolling.

This is why I find it odd; There's effectively no load on the engine in both P or N.

Hopefully the UEC works

[lucasryanmartin]

Sorry but UEC?

Ive sort of been putting my car through its paces last few days....and since then i havent been able to fault it

EDIT; its now doing it in neautral aswell

[kabdizzle]

I have the same car and had a similar issue, replaced the maf sensor, cleaned all 4 avcs solenoids, replaced o2 sensor, scrubbed the throttle body but it ended up being a broken vacuum hose from the blow off valve to the intake pipe. Might be worth thoroughly checking for any air leaks, it really was a bitch to spot.

Kab