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Jzx90 G4x iacv problems

Bevan Sutherland

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Hi guys I’m having issues with my jzx90 plug and play ecu , have some all pre start checks and car does start fine but idles very high and is sucking air from my iacv which had been previously changed from having the vacuum hose to now just having a filter on the back as I’ve gone single turbo , this system worked fine on the stock ecu but now seems to be causing a massive vacuum leak, the stock iacv does not seem to be working at all but I’m not sure if I’ve missed setting something up in the ecu to remedy this ? Any help would be greatly appreciated 

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Check the idle status runtime to confirm it is entering idle conditions and is not locked out.  Reduce idle base position to close the valve more. 

For idle it should work fine with the valve vented to atmosphere as it is now, but before tuning you are going to need to plumb that valve back to how it was designed to be, one side to manifold, one side to pre-throttle intake piping.  With it vented it will be a big boost leak when not in idle conditions.  With a stepper motor type idle valve you cant just close the valve when boosting as they are too slow to open again when you lift off so it would just stall all the time.  Stepper motor valves generally need to stay open all the time when not idling to catch the engine on the way beck down to idle. 

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