Hey guys, 4 months ago my ute started to rough idle and then completely stop idling. From startup or stopping at lights it simply wouldn't even try to idle. I replaced the IAC valve, which worked for a week. Replaced it again with a better part and it worked perfectly for 4 months. Now it's happening again, this time I gave the Throttle body a good proper clean out and immediately afterwards the idle was perfect for a few days. Now it idles at about 300rpm, occasionally stalling. Turning on the AC went from increasing rpm this morning to dropping the rpm so low the car stalls. Currently I've got it idling but after I accelerate it will drop to basically nothing, sometimes it'll stall and sometimes if I give it some juice and slowly let off the pedal it'll keep itself going. I've tested the Throttle Position Sensor and it seems to be working although the resistance did seem to jump around a bit, could be the cheap multimeter though. I'm thinking maybe an O2 sensor and I seriously hope it's not the ECU. I've got a PCV valve being delivered so I'm replacing that regardless. Any ideas what could be causing this? Sometimes unhooking the battery and hooking it up again will instantly fix it as if nothing was ever wrong. Immediately after cleaning the Throttle the idle jumped from about 800rpm to 1000 and it has slowly been dropping until now. I've got no other performance issues, in fact just by trying to fix this issue the performance seems to be improving. Besides the idle and excessive oil burning it runs pretty well at 370 kms. My next idea is to manually adjusting the throttle close positon but I don't think there's a screw for that. Might rodgey dodgey one up myself if I really have to but I don't want to do **** like that in case it's serious. Any input would be appreciated, thanks

 

I'll add that my battery + terminal had a pile of blueish powder all over it which I left there way too long. I finally cleaned it up and that seemed to fix the idle immediately and the engine seemed to run smoother. But that may have just been because I'd unhooked the battery and it decided to idle again for whatever reason. My understanding is that the reboot on the ECU forces it to default any calibrations and it will slowly go back to whatever idle settings it had "learnt". Also external heat seems to play a role as when the issue came back after months I was at a quarry and it was exceptionally hot. Same as today when it started doing it after I'd thought I'd fixed it.