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Engine Tech Technical discussion related to all relevant engines such as KA, SR, RB, CA, 2JZ , L24/26/28, VG, VQ, and LSx series.


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Old 05-10-2018, 07:41 PM   #1
unicoder
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KA-T AFR Changing with Accessories on/off

KA24DET, ISR Kit, Enthalpy tune.

Everything on my kit runs awesome so far. I avoided driving in the rain because it "didn't run right" and due to my schedule I never drive at night so It took me a while to isolate this issue.

- With no accessories on. I idle at 14.5 AFR and everything is fine. WOT at 11-11.5
- Headlights on, it wants to idle at 12 AFR or slowly rise to 13. it also drives really rich and WOT is like 10 AFR.
- Car is affected by the changes, it's not just the gauge. When the headlights are on I can spool but just no pulling, and when they are off I get up and go.

My first thought was alternator (I read this thread http://zilvia.net/f/showthread.php?t=116171)

At idle my battery is 13.5v and 13.2v when turned off. Doesn't change much when I turn accessories on.

Should I bench test this alternator? Or should I look more into adding grounds to the engine? Thanks

edit: also just took my digital mm and tested continuity from negative of battery throughout the engine bay, got 0 on everything so I think im good there
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Old 05-11-2018, 08:09 AM   #2
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Add some grounds to your set up. Add a separate ground for your alternator to chassis, and add 1 or 2 more engine to chassis grounds. I used 8GA wire for my ALT and 4GA to engine to chassis.

This solved many similar headaches for me.
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Old 05-11-2018, 10:42 AM   #3
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Alright, the issue has also changed as of this morning.

IDK why the battery is charging a good 14.2 now and handles the accessories. IDK why it is so intermittent like that (likely the ground issue, will totally do that)

But now here is the problem.

AC off - idle around 900, fluctuates like it might die, AFR slowly raises from 14 to 17+
AC on - idle steady 1500, 14.5 afr

I just fixed all my vaccuum leaks so IDK what is causing it. Im pretty sure the raising AFR could be an exhaust leak, but strange it doesnt happen with AC on
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Old 05-11-2018, 05:11 PM   #4
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update, found a boost leak in the EGR blockoff plate. Resolved that and it fixed a lot of it.

Still have the issue of headlights affecting the afr to run rich, but i got a ground wire just need to ground the alternator and whatever else i can. wish me luck
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Old 05-17-2018, 12:14 PM   #5
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I have this problem too, I fixed vacuum leaks and it got a lot better, but it seems like the grounds are the next thing to try..
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Old 06-17-2018, 02:31 PM   #6
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Heads up. I bought a negative cable from the parts store with lugs on each side. Grounded my negative terminal directly to the engine and so far so good. AFR seems to be back to normal
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Old 06-18-2018, 08:10 AM   #7
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Thanks for the update. I will be sure to try this.
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Old 06-18-2018, 11:22 AM   #8
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Went back and added another ground from engine to chassis just to be safe.
Also make sure you don’t have a knock sensor code 34
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Old 06-21-2018, 01:36 PM   #9
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I actually do have the code 34. It comes and goes. I replaced the knock sensor but the code still pays me a visit every once in a while. I have knock analysis off in nistune though so it doesn't affect the driving.

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