Idle issue XR8 help..

[EATHSV]

Hey guys got an issue with the XR8

If its left to idle for any longer than a minute without being moved it devolops what can only be described as hunting. It bounces back and forth between 1000rpm and almost stall.

So far I've tried the following...

Cleaned throttle body
Cleaned MAF
Replaced O2 sensers
Fitted Iridium plugs
New Leads
MSD coils
Reset the computer

What have I over looked?
Been trying to nut this out for a while any ideas would be appreciated.

Thanks guys.

[Mr_Monty]

Set Idle screw to correct setting (i think is 600-650rpm) with a .7mm feeler inbetween screw.

mine was over done and hanted like nuts..... aswell it did this with a faulty brand new Maf i brought from skonsi off ebay that he wont replace ($350)

possibly check and clean connections to maf, cmp and ckp and o2's connectors.

you said it does it after a minute, the ecu isnt using o2 data until after a minute or so until the sensors are warmed up after start up. im sure i have ready at idle there temps can drop causeing a bad readings aswell. so perhaps check the heating cirtcuit is good (first check Hego fuse)

forgot vaccum leaks they do it too, theres an L shaped Elbow at the back of the intake manifold, carries the vacuum the aircon system controls etc, just put a cable tie around it and pul lit up tight, should do as a temp fix.

thats all i can think of.

best of luck

[CRAIGAU3220]

Hey Monty can the switching time to o2 reading be changed by a tuner if you have a flash box? or, other than checking Hego fuse how would you check heating circuit.

The reason i ask is quite often after about a minute from cold start mine will hunt for a short time before it recovers.

Thanks in advance, Craig.

[james22]

Reset your BASE idle.

As monty sort of said.

What he didn't tell you, is that to do this you need to disconnect the IAC (Idle airspeed controller)

Procedure as follows;

Run car to normal operating temperature.
Disconnect the IAC connecter.
Wind the idle up manually using the bolt on the t-body (so your car will actually start, without stalling - when you disconnect the iac it will just want to stall)
Unwind the bolt until your idle sits at 550-600rpm?
Stop car, reconnect IAC connecter
Reset ECU

That has set your base idle, after a little bit of running your idle should settle back to approx 800-900rpm.

If it still plays up after this... maybe check your TPS voltage (position).. although I'm unsure if this would have any affect on your idle.

[Regan]

G’day,
I have an AU XLS V8 manual ute with 250,000km under its belt now - I’ve owned it for 6mths and its been a slow process tidying things up - first was a full service - all oils - fix
oil leaks from the gear box speedo sender - rear gear box seal - power steering leaks - diff leak that I ended replaced with a complete LSD XR6 BA swap out as the backlash and the whine coming out of the original diff one had to almost wear hearing protection it howled that loud - the a/c was a bugger to get going - that had to be out sourced to auto electricians to get to the multiple failed connections - new struts and brake pads - bump stops in the front - then the task of getting rid of the dipping idle - I scoured the forum and other sites looking for answers then started checking and cleaning components one at a time to find the cause of the idle dip/drop fluctuation - the induction had one of those wonder spray cleans befor I picked the ute up which I’m not a fan of - from the air box through to the intake plenum - I replaced the ICV as it looked old but unplugging it and plugging it back in suggested it was working - the bypass valve and ports had a lot of crud in them so I cleaned them and ran it like that for a few weeks before fitting a new ICV - no change to the idle - I then set the idle speed with the new ICV disconnect - I had to turn the throttle stop in near two and a half turns to achieve the desired idle then reconnected the ICV - with the idle set the fluctuation was still there but was better to drive stalling the engine less but you had to keep a light load on the throttle at low speed or it would jerk violently - so the MAF was cleaned next - it didn’t look to bad but had a little bit of crud around it - so I cleaned that gently as some stuff was stuck to the heater wires - it used to run an oil type K&N filter which may explain the stuff stuck on the filament - that made a little improvement with a steadier idle and less rpm dip but it still wasn’t sweet to drive as it would jerk at low speed if not keeping a light load on the throttle - next up was the air temp sensor - no difference - I should also mention I changed out the PCV as the original was worn and I thought I might be on a winner but no - I also looked for vacuum leaked but the dipping idle didn’t support a vacuum leak so today I removed the throttle body - it looked ok with a little carbon around where the butterfly rests at idle - I cleaned the bore and butterfly running super fine wet and dry around the butterfly edge and the bore and fitted it all back up - on first start the idle was at 1000rpm so I rest the idle and to around 600rpm - there was a noticeable difference straight away - I took it for a test drive and what a difference - crawl in first and no jerkiness with no load on the throttle - no idle dip or fluctuation - you can now creep up to a stop with no jerk or dip and a smooth idle - I should have tackled the throttle body first but was told it’s been cleaned by the magic dump of spray up it’s nostril - all I can say is the obvious is some times the obvious - it’s now sweet as to drive - best of all after a 3600km road trip towing a light 300 + kg load and fitted with a big *** canopy it averaged 8.5lt/100km - I’m so impressed - might not have the mojo of the bigger boss engines but it’s still a lovely little V8 that can growl when you need it to and hum a sweet exhaust note hour upon hour on the open road - now to sort out the cruise control