Weird surge idle

[Terminal_Crazy]

Evening guys.

I wondered if anyone had any ideas or suggestions.

I've been playing with my 16188051 LT1 tune and it's developed a wild surging idle. Just about all the data is surging up & down. Old tune still does it.
NO Fault codes
I've also had my "Check guages" light flickering on and off. Just yanked cables behind drivers side of the intake and it went out so I need to chase that but the surge still persists.
Car warms up ok to 80C then goes crazy with surge.

IAC swings 80-140 but i can't tell if it's fighting it or causing it. IAC isn't that old

I'm not quite 100% certain it isn't the tune but an old tune which passed the emissions does it.
I've also switched injectors back to a previous set and can't rule them out yet also *** More likely these than the tune but they didn't do this when I first swapped them.

TIA
Mitch

[kur4o]

How is the spark idle correction set. It is much better for controlling idle than IAC valve.

It is either spark, fuel or mechanical.

[Terminal_Crazy]

I've zeroed it out for now. spark is pretty stable and hasn't changed. The surge cycles about 1-2 seconds
I've tried to slow the iac down some without any success.

I suspect these injectors might be struggling at a 1.2mS pw. They're still on the rich side atm about 0.92 Lamda.
I suspect a "misfire" might cause a lean flare, but this oscillation is very regular.

Thanks
Mitch


The last injectors were idling around 1.6m$, both are 45lb

[kur4o]

I've zeroed it out for now.

You can revert back to stock, It offloads IAC movement on small rpm fluctuations, and adjust it really fast. You can even expand it, if that helps.

Also make sure idle spark table is not maxed out so it have some room for adjustments.

Than we will look at injectors.

[Terminal_Crazy]

Thanks kur4o
I'm pretty sure it was the injectors struggling at a low pw below 1mS
Car ran fine around 13.5 afr then trim the ve table 1 cell & we were up around 15's afr.
Idle was OK. It was when the rpm rose and map fell the pw fell below 1mS.

I've swapped the injectors back. These are idling around 1.6mS so we're off playing again.


Thanks
Mitch