Hey guys,
I have a 1999 TH wagon about 160,000kms on it now. Started having issues around 3 months ago with the idle. It would be fine when cold but once warmed up it would get really low, about 500-600. Worse under load, eg lights on or music playing loud. Now it is having trouble when cold now, won't hold revs until warm then sits at about 500. It always wants to stall, especially under load, tries to stall around corners or hard braking etc.

Recently replaced items/services:
-ISC
-O2 sensor
-spark plugs
-front and rear rocker cover gaskets (had a seriously oil leak)
-Throttle body cleaned

Currently have no audio gear installed and no other electronics to drain the battery but it only lasts about 3 days not driving it before I won't be able to start it. The battry is about 18 months old, D34 yellow top. Has been drained completely before, may this have killed it? Could it be the alternator or something related?

Thanks,
Samm

Sounds like alternator to me!

I had this problem, kinda. It would want to die right after starting 3/4 times. Went and had the auto store check my battery after fooling around with the isc screw, and they couldn't even get a reading on the battery at all. Replaced the battery and everything was good after. I think about 3 times it actually killed the engine.

Though, the alternator should be recharging it. So I'd maybe start with the alternator too.

Purchase a Projecta IC700 or IC700W (7-stage) battery charger (full AGM mode), and run a rejuvenation cycle over it. I've seen this charger bring 2 seemingly dead batteries (even after a store battery test) fully back to life. Even if it doesn't in your case, a good quality battery charger is a good investment :). Just note these work differently to normal battery chargers, a simple 3-stage etc will not do.

I suggest the IC700 or the IC700W because it can be bought for a decent price (around $130 on Ebay), is from a proven brand, and has a mode specifically tailored for AGM batteries (which the D34 yellowtop is). You could also go for the IC1000, which is $169.