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Hunting Idle

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Hello everyone, I'm having a rough time with a hunting idle.

Nissan QR25DE (8.5:1 CR, Garrett GTX3071R, mild street/track cams)

Haltech Elite 1500 with DBW (Nissan 07+ Hitachi TB)

Walbro 525lph pump, 1200cc Five-O Motorsports Injectors

Not sure what else you guys want for setup information

The car will idle well when the charge pipe is disconnected, decently well, 850rpm, lambda 1.0 target.

Once I connect the charge pipe, O2 reports .75-1.25 (target is still 1.0), struggles to maintain a consistent idle, and it will eventually stall if left unattended (throttle input)

Here's a link to my google drive for my datalogs and the current tune on the car:


I've been struggling with it as has my tuner.

I see a bunch of things all fighting each other. The idle air and TPS are trying to control the idle, but the operating conditions of the engine are changing both the target Lambda, and I see pretty wild swings in the ignition timing. Particularly, I think the 24 deg of timing when the engine is about to stall at 750 RPM might be excessive. Overall, I would be trying to reduce the timing to about 10-12 degrees at idle

So, I would look at the range of RPM & MAP that the engine is operating in when hunting. Initially I would smooth the ignition table in this area. I would experiment with using a single lambda target, and changing that to see if another value will smooth the idle (try .92 - .98 la). I often find that if I just richen the mixture the engine will not hunt as badly and smooth out.

If you can, consider disabling the idle control to get the engine running steady at different fixed throttle positions.

David, thank you for your reply.

Would you be able to perhaps show me an example of the conflicts you're talking about? I'm really very new to tuning and I definitely learn visually/practically.

I'd like to have the idle target set to 850rpm, which it will do with the charge pipe disconnected.

I've tried to make a screen capture movie showing how I looked at your data.

Here is the link to the file if the above isn't displayed (it's a quicktime movie):


Huge help Sir, thank you, that definitely makes more sense to me. Video ftw.

I'll toss in some more even timing across the idle range of the engine, and report back my findings. I just find it interesting that when the charge pipe is disconnected all seems well, but with that added air flow it starts doing weird things. But this will be a great start to get it idling well.

Aside from the idle, the car runs well and makes plenty of power throughout the rev range.