Originally Posted by
gcfcos
Hi thanks for the reply. It doesn't have closed loop, it's just a basic stage 3, greens and 3 bar etc with a stage 3 msd chip. It idles fine with the stage 1 pts chip. My friends Cossie has the exact same set up which I fitted for him and his idles fine. Could anyone tell me how to test the iscv? And what voltage etc I should be getting just to rule it out. Thanks
If the base idle is set correctly with the Iscv unplugged then it should never drop below this. The valve only opens and closes, when it's closed it should sit on the base idle which you set at 900 rpm.
If the idle still is unstable it can sometimes just be that the map is referencing a load site that's not quite suited and it has a big effect in the idle speed and it will be bobbing about picking up on these sites.
You can do some testing your self, ie what is the Co level? Can you richen it up and does that help? Does adding .1 .2 .3 .4 .5 bar of fuel pressure fix the idle stumble? If so you can relay this info back to msd and they can try to fix it in the chip although it's often hard to know where it's referencing and what load site it's on which is why bits like this are so easy to fix when mapping live, but can be a nightmare to try and fix off the shelf