IAC valve gasket mod causing high fuel trims

[Adam Vinnicombe]

To all you clever people please explain something to me.
Now my new edge fuel trims where spot on before I done the IAC mod which restricts air flow at idle to help bring down the rpm faster and it has worked but since fitting it my STFTs have shot up from around zero to plus 12 & 14% and LTFTs are also on there way up as well. Now as soon as I remove the restrict IAC valve gasket all the fuel trims drop back to normal. Now this is my issue that I just don’t understand, surly if I’m restricting the air flow at idle the engine should thing it’s running rich and reduce fuel flow and give me a negative fuel trim not a positive fuel trim?
Can someone please explain to me what’s going on

 

[Silver95bird]

if i had to guess, the issue is in the programming. Despite the restriction, the EEC is commanding a higher RPM than the airflow allows, and commanding the fuel for the airflow it expects. I expect this issue to be worse on cold startups, and probably less once it goes open loop.

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