Weird Idle issues

[The_Hawk]

my idle seems to be directly related to voltage drop. even when cruising at 100 if i press up on the two front windows when they are completely closed the car feels like it looses all power for a split second, it almost feels like its hitting the rev limiter.

it seems to also happen when i have music up a bit louder than normal.

Power windows I can understand a little more since an electric motor can draw insane amounts of current. I wouldn't have though the stereo would have had the same issue, but then I have noticed the interior lights dim in time with the bass beat and I don't have anything approaching a high powered system. Basic Pioneer headunit, Pioneer 200W amp and a set of Sony 6x9's.
Would have though it would have been even less of a problem since the amp draws direct from the battery too.

[BlackVr6ix]

I think its probably got a lot to do with the poor earthing of the engine and chassis, poor supply to the main fuse box as well as the potential of my alternator being 205k km old!

once i have some time off work i will be investigating, however last time i had a clamp ammeter on my car it was producing ~40-50 amps at idle which is pretty high even for a 120amp alternator like on our cars.

[Jmac]

Earth cable to the gearbox goes green on them mate. Check for voltage drop at the earth cable between earth point and cable. any more than 0.5 volts then you have an issue. Drop testyour battery as well ( in lamens terms load up the battery and check the cells) Also test the alternator outut at the D+ wire which is the blue one. This will tell you if the reg is ok. But yeah Earths are crap on them after a few years. As i mentioned the cable goes green with corrosion thus lots of resistance.
Mate if you have VAG COM you can check the voltage at the ECU when its running, this will tell you that 109 or 30 is ok. When these start to go you have starting problems.