usmonaro

Tried searching couldn't find. I have a 2000 Z28 A4. Idle in drive is about 650rpm according to the stock tach. Is this too low, and is there a way to raise the idle properly? Car runs and drives good. Just wondering.

RPM WS6

iTrader: (3)

The stock tach is almost never 100% accurate. You will need a scanner if you want to confirm the true idle rpm.

Stock GM tuning for these cars results in the following commanded idle speeds:

A4 cars: 650rpm in park/neutral, 550rpm in gear
M6 cars: 800rpm

The above is true for all years of LS1 F-body.

Idle speed can be modified via custom tuning. As these engines have an IAC motor to maintain commanded idle speed as temp and load conditions change, there isn't much you can do to adjust idle speed without some negative side effects (other than the proper method, which is custom tuning to change the commanded idle in the PCM).

Chawlz

there is a idle adjustment screw on throttle body. it is upside down, cant see it without mirror. takes a small torx bit, cant remember size. unsure about how it will affect stock tune though.


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usmonaro

Thanks bunches guys, had a 04 GTO m6 and it idled around 800, its tach was very accurate. I just though 650 seemed a bit low but if that's what GM tuned to probably had a reason.

RPM WS6

iTrader: (3)

The IAC will fight minor changes to this screw, as much as it can. Larger changes will infact raise the idle speed, but can also cause idle hang, cruise control effect, and high idle codes.

If you have a stock cam, there shouldn't be any need to adjust the idle speed.

redtan

iTrader: (5)

For an automatic that's not low at all...my GTO was at 550 stock.