Idle Issue

Hi there. I am based in the UK and I’ve got a Holden Monaro LS1 VZ with the ETC. I’ve had a cam fitted (mild but I don’t know the exact spec) 243 heads and a PWR 102mm TB which feeds into an LS2 intake manifold.

I’ve got a weird idle issue that only presents itself when the AC is switched off. If the AC is switched on all is fine.

This is the problem. If I pull up to a set of traffic lights and sit there with the engine idling after around 15 seconds the revs rise up to around 1600rpms without me pressing the accelerator pedal and then within 4 or 5 seconds the car goes into engine protection mode and throws a P0068 code. If I hit the AC button within around a second of the revs rising it settles back again.

This is driving me mad. I assume there must be something in the tune that needs a tweak?

Has anyone experience this problem?

IMO,

a 102mm TB on a 5.7 is going to cause you problems in itself; it's way too big.
Also a stock LS2 intake is inferior to the o.e. LS6 intake.
If you ran the LS6 manifold and a 78mm TB I believe your problems would be gone and the car would also be quicker!

Thanks for that. Gonna consider changing the 102 and fitting a 90 tb instead

Off topic for here,

but you aren't able to receive PM's

The quickest combination for a 5.7 on the street is a good quality (modified) 78 TB and the FAST intake.
PM if you need clarification.