VF V6 Evoke. Fault codes x2 and rough idle every 30 seconds or so

[Sfr rob]

Hey guys. Just brought home a second hand evoke with 98k on the clock.
Noticed when it is in park the revs drop and the car starts idling like a bag of crap. It then starts idling fine for another minute or so then drops and idlescrap AGAIN. If it is in drive it does not carry on like a pork chop.

The car drives fine and no rough rpm/surging etc. Only happens at idle.
The engine light came on as I reversed into my driveway. I checked the fault codes and it reads
P0171 & P0174
I cleared the codes and the car idled fine.
Now it had the engine light on at the dealership and they said they'd change the O2 sensor before I picked it up which I highly doubt they did.
And NO, I am not taking sure it back to them, they're 3 hours away.

Does it sound like it would be an O2 sensor issue?
Or could it be a dirty maf sensor?

Would my first port of call be to replace the sensor?
Where is it located exactly and where should I buy one from.

This is my first Holden so I don't know too much about them.

 

[tml678]

Those codes relate to both banks running lean, I'd be having a look to see if it IS actually running lean. If so you need to fix this issue rather than just throwing a new O2 sensor at it. You don't want an engine running lean for too long and the ECU can only do so much to compensate before it maxes out.

 

[stooge]

They are codes for system to lean it is quite likely they didnt change the o2 sensor because... dealer.

 

[Sfr rob]

Yeah, I read what the codes meant in the scan tool.
So what do you reckon it could be?

 

[lmoengnr]

If its running ok whilst driving, but having a cyclic idling problem, I'd be looking at the throttle body.

 

[Sfr rob]

Just took it to the shops and back. Ran perfect. Check engine light didn't come back on after clearing it.
I will pull the airbox off and see if the throttle body is gunked up.

Cheers.

 

[BlackVXGTS]

The attached reference may help you:

 

[Sfr rob]

Thanks mate.
What an awesome forum. So glad there are still people around who are willing to help!

 

[Sfr rob]

Checked the throttle body this arvo as the car started doing its lumpy cam idle thing after the school run. No CEL on thr dash.
The throttle body wasn't very grubby, gave it a little wipe down anyway. Noticed the breather pipe from the passenger side rocker cover wasn't hooked up so I plugged that back up. Fired it up and it seemed to idle nicely.
Not sure what's going on. I will see if it logs a fault code again tomorrow .
If it happens again, what would you be looking at checking out?

 

[Sfr rob]

I am unsure if the ventilation hose was disconnected before I undone the throttle body clamp and removed the little intake muffler thing. But if it was, that would mean that it was getting unmetered air into the throttle body......no?