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Searching idle at 65*-70* C

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Gentlemen -

I was wondering if anyone has come across this problem or could offer a little insight - I think I've ironed out a few issues on my tune but around 150*F / 65*C my car starts to search at idle. This searching usually is around the 5 - 6 minute mark. I can usually save it by giving it a little throttle and or holding ~2000rpms for a minute or two where I can get the temperature to rise into the 180*F / 80*C where the idle seems to settle back down. I'm not very deep with my tune and/or map as I'm gradually getting the tune in-order. My available tables that reference coolant temp all seem to be in order.

It's a twin turbo 350z running the Haltech Pro Harness ECU - I can upload my maps and/or data logs if that'd help.

Thanks in advanced - James

There are a few potential reasons for the sort of idle problems you mention. Quite often something that's overlooked is a lean AFR causing the hunting as a result of something unusual going on in the warmup enrichment table so I'd check this and make sure your AFR is consistent across the area you notice the problem.

Next would be the base duty cycle for the idle control system. You may find this table needs some work in the region your having trouble.

Lastly if you haven't already, I'd suggest using the idle ignition function to help stabilise the idle speed using ignition timing.

Andre - thanks for the quick reply.

something unusual going on in the warmup enrichment table so I'd check this and make sure your AFR is consistent across the area you notice the problem.

Meaning my coolant temp correction comp table? I'm adding 0% from 122*F(50*C) through 260(126*C)

"Next would be the base duty cycle for the idle control system. You may find this table needs some work in the region your having trouble."

Are you referring to the ignition base map and coolant temp correction maps in general? My map doesnt appear to be horribly off. Can I set my timing advance, from 30*C to 100*C, to 0 in an attempt to isolate the problem? Could I do this with the fuel side (coolant temp correction) too?

Lastly if you haven't already, I'd suggest using the idle ignition function to help stabilise the idle speed using ignition timing."

Forgive my ignorance, but I'm not familiar with the 'idle ignition function'. Might this be a feature on the newer Platinum Pro Z33? I've got the Platinum Pro Harness PNP. Could you elaborate a little bit on this?

What are your air fuel ratios doing across the area where the engine is hunting? While you should be ok with 0% additional fuelling at 50 deg C, this may not be the case and perhaps you are a little lean until the temp gets up.

Setting your ignition to 0 won't be a great idea as this will drop your idle speed. If I'm having trouble with idle stability I will often start by setting the ignition timing to a fixed value of say 15 degrees across all the zones the engine is idling in. This makes sure that the ignition timing won't effect the engine torque. For the same reason it's important to make sure all of the fuel cells in the idle area are tuned accurately. If you have one cell that's very rich or lean then this can effect the idle stability.

The idle ignition function alters the ignition timing based on the error from your target idle speed. Check out this webinar that explains the function on the Link platform - https://www.hpacademy.com/previous-webinars/how-to-setup-idle-ignition-control-link-vipec/.

We are using the Platinum Pro plug in in our Z and I've attached a screen shot of the function.

Lastly I'd suggest logging what is happening across the point that the idle becomes unstable. This may give some better insight into what's going on.

Attached Files

Thank you Andre -

AFRs are right around .90lambda

I mis-spoke/typed, not set my ignition base to 0 but rather my ignition coolant temp compensation to 0. Which is set at 0 from 50*C through 100*C. My base is currently between 15 and 18 degrees in my idle region but will set them all to 15* before my next startup.

I'm running a generation earlier Haltech - so I don't have the predefined ignition control.

I believe I watched the idle ignition webinar but will watch it again tonight. On that note - I've got 2 unexpected payment (selling a few things online) that will fund the starter pack - which I'm excited about. So I may start from scratch after the coursework.

As a rule I seldom use ignition trim vs coolant temp. I've never really found it to be useful but that is just me. It sounds like your AFR is on point. Using ignition control vs rpm can be helpful in stabilising idle speed. If you don't have a specific function to do this you can get a similar effect in the main ignition table. This has some pros and cons though so it needs to be approached with some caution.

Logging what's happening is probably the best place to start. I think you will find some great value and helpful material in the starter pack :)