link G3 rough idle
 

i have a linkplus G3 running the 03 jdm sti motor in my foz, it is wired up to a plx devices wideband 02 sensor (stock 02 sensor removed)

afm has been deleted & its running off the link MAP sensor

i have had issues with the idle wandering around a bit even when the motor is warm

just wondering if a dead wideband 02 sensor could cause this?

& yes i have replaced the IACV with a brand new one... & the problem remains

what happens when you unplug the iac?

just tested it then, revs sit at about 1000rpm at idle, unplugged the iacv and the revs went up & sat at about 1400rpm

You need someone to have a look with a serial link, get in contact with Leigh Hynes, he's the Link guru. He'll come up from Busso to check it out.
AFAIK if you ring S-technic they'll be able to put you in contact with him.

yeah the whole setup was initially done by Leigh when it was installed in foxeys car, i bought the engine/ecu/loom off foxey & installed into my foz,

upon install i got foxey to hook it up to the laptop using pclink & he checked everything was okay... & it was, i've had it retuned by the guys at ASG (since it went from having a fmic on foxeys to tmic on mine)

the idle has always wandered around a bit though so i then replaced the iacv with a brand new one, also replaced the fuel pump

I've been doign a bit of research & it seems quite common for wideband 02 sensors to die after a while, especially when they are installed close to the turbo (mine is installed in the stock 99 wrx 02 sensor position right behind the turbo)

I would have loved to of got Leigh to tune the car but due to him living so far away now & rally commitments it was pretty difficult

Can you do a 'free air calibration' on the PLX controller & sensor like you can with the Tech Edge units?

My sensor is in the same location & it's still fine after nearly 2 years constant use.

The sensor can (& will) age over time & a quick recalibration should have it back in spec if it has wandered.

Most ecu's ignore the wideband @ idle and lock in a certain area of the fuel & timing maps at idle (low tps & under a certain rpm) though (to help prevent idle hunting with bigger cams).

Checked for vacuum leaks?

cheers ross, will look into the calibration, could the crank angle sensor cause up/down idle too? the worst time it does it is when the motors warm and you turn it off then restart it, unplugged the iac whilst it was doing its thang and made no difference still wandering up & down

yeah no leaks anywhere, car runs mint other than this, no surging, spiking or any hessitation or anything, just this little niggling thing thats stumped me

edit: na plx doesn't ever need free air recalibrating

found there is a test but i need the gauge to do it, better go & order one

Factory ECU's use A/FR sensor feedback at idle... Links don't used closed loop at all unless its been switched on, and it can be set to go into closed loop at any RPM above 500, its all in the tune.
From my experience, Leigh is the only guy in Perth, maybe even W.A. that can get a Link running nice.
A couple of things I've found with Links that may be the issue.
THe idle clamp vacuum setting is incorrect, the enrichment compensation is incorrect for hot starts, the IAT compensation is incorrect, or the TPS is not set correctly.

Remember, just because you have the wideband connected, if closed loop control is not switched on, it wont be having an effect on the ECU.

cool, thanks for the tips, maybe i should be seeing leigh for my next retune, does he do any work up here anymore? i just want to make sure everything in tip top before i get it tuned again, will get the afr gauge anyway

just swapped my crank angle sensor so i'll see if that has any effect, i'm not so sure its in the tune as it would be there all the time wouldn't it?

Best to ring S-technic, as Leigh is still the W.A. agent for Link, I'm sure he will still come up for tuning duties. Don't quote me, but I think its part of the obligations for Link agents.
It may be a simple adjustment is all thats needed.
Like you said, it may be a faulty sensor, but, without knowing how the Link is set up its hard to tell.