IAC flaring on EFI Hardware Throttle Body
Posted: Mon Mar 25, 2024 10:19 am
Hi All,
Bit of a weird one but I thought I'd reach out to the brains trust for ideas.
I'm currently tuning a 304 with an Edelbrock dual plane manifold and an EFI Hardware 750CFM throttle body, it runs the stock GM IAC with the smaller pintle (Pre LS) (taken directly from the OEM throttle body and is a known working unit).
The problem I'm experiencing is randomly at idle the IAC is shooting up to around 100-150 steps then slowly closes back down to it's resting idle state of around 10-15 steps. Also when changing from Park to Drive the IAC will flare up to around 100+ steps then drop back down over 5-6 seconds to it's resting idle position, the same thing then happens again when I go from drive back to park it will open the IAC right up and idle at 1500-1600RPM for 10 or so seconds then drop down.
To then add to that when cruising at 50/60kph in 4th the IAC starts to creep open when coasting to around 60-70 steps and basically keeps accelerating the car when my foots off the accelerator.
It cold starts perfectly with my desired warm up steps etc, and when watching the warm up process on the live dashboard I can see the steps behaving, but once the cars warmed up it's all over the place. If I disconnect the IAC and run solely off the throttle stop screw the car is perfect, the problem is I have an astra power steering pump and a BF thermo fan and I like to have the IAC to compensate for when the thermo kicks in and adds load, otherwise to be honest in the Adelaide climate I don't really need idle control that much other than for cold start in winter.
I've swapped over to my spare IAC to test to make sure it's not a fault sensor and the behavior is the same.
I've tried adjusting the maximum base parameters for drive/park etc and nothing seems to make much of a difference, the IAC just has a mind of it's own.
Any ideas would be much appreciated.
Thanks
Bit of a weird one but I thought I'd reach out to the brains trust for ideas.
I'm currently tuning a 304 with an Edelbrock dual plane manifold and an EFI Hardware 750CFM throttle body, it runs the stock GM IAC with the smaller pintle (Pre LS) (taken directly from the OEM throttle body and is a known working unit).
The problem I'm experiencing is randomly at idle the IAC is shooting up to around 100-150 steps then slowly closes back down to it's resting idle state of around 10-15 steps. Also when changing from Park to Drive the IAC will flare up to around 100+ steps then drop back down over 5-6 seconds to it's resting idle position, the same thing then happens again when I go from drive back to park it will open the IAC right up and idle at 1500-1600RPM for 10 or so seconds then drop down.
To then add to that when cruising at 50/60kph in 4th the IAC starts to creep open when coasting to around 60-70 steps and basically keeps accelerating the car when my foots off the accelerator.
It cold starts perfectly with my desired warm up steps etc, and when watching the warm up process on the live dashboard I can see the steps behaving, but once the cars warmed up it's all over the place. If I disconnect the IAC and run solely off the throttle stop screw the car is perfect, the problem is I have an astra power steering pump and a BF thermo fan and I like to have the IAC to compensate for when the thermo kicks in and adds load, otherwise to be honest in the Adelaide climate I don't really need idle control that much other than for cold start in winter.
I've swapped over to my spare IAC to test to make sure it's not a fault sensor and the behavior is the same.
I've tried adjusting the maximum base parameters for drive/park etc and nothing seems to make much of a difference, the IAC just has a mind of it's own.
Any ideas would be much appreciated.
Thanks