Possible Lean misfire help

s300 and SManager software questions & answers
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dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Possible Lean misfire help

Post by dluder »

Hey guys I've been fighting with my car for about a year now and I'm still no closer to figuring it out. I'm hoping y'all may have some fresh ideas.
Build
2000 prelude
H22a4
11.1
Pro 1 cams degreed
Supertech vt
Ported intake 70mm tb
Lightly ported head
525cc fic injectors
H,I,e
Hamotorsports ecu s300 v3
It ran great for the first few months but then it started going lean at idle wanting to die
Now I'm getting what appears to be a lean misfire under low load. It will buck and kind of cut out at a steady rpm. Most of the time the afr will still read good 13.5-14. However on take off or sometimes at a cruise when I accelerate it'll stumble and go lean. It tends to get really bad with a afr of 14 or more. So I've been running rich when I drive it. This all started with a perfectly tuned map.
I've replaced
All sensors, plugs, wires, intake gasket, injectors, injector pigtails, ecu conversion harness.
I tried a friends ecu and s300
Compression 225
Leak down -3%
Lol idk what to do besides burn it to the ground.
No issues show up while datalogging and no codes.

dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Re: Possible Lean misfire help

Post by dluder »

I've also replaced grounds, distributor, fuel rail and fuel filter. Fuel pressure at filter was 45 I think. It was definitely in range though. It reminds me of a injector cutting out but im not getting a code and it's not showing on the plugs. The only thing I can think to do is run new grounds from ecu to injectors. Injectors are getting good voltage.

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Spunkster
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Re: Possible Lean misfire help

Post by Spunkster »

Has this been properly tuned on the dyno?

Have you discussed this issue with your tuner?

dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Re: Possible Lean misfire help

Post by dluder »

Yes the tune is definitely not the issue

dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Re: Possible Lean misfire help

Post by dluder »

I've had quite a few friends and tuners check it out with no luck. Do u think a injector could be losing ground without throwing a code? They seem to be getting correct voltage and look normal with a noid light.

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Spunkster
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Re: Possible Lean misfire help

Post by Spunkster »

If you have tried a different ECU and s300 then you have ruled out Hondata/ECU as being an issue. It sounds like a mechanical or wiring related issue which can be difficult to diagnose. You will have to use process of elimination.

dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Re: Possible Lean misfire help

Post by dluder »

Thanks but I've already done that and I'm all out of options. I was hoping someone here had some fresh ideas. I've literally checked everything. I thought it may have been the s300 cause the red light was on but I sent it to yall and it tested good. When I used my friends ecu/s300 it ran totally different on the same exact tune. It ran alot better with his but the miss was still there.

dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Re: Possible Lean misfire help

Post by dluder »

The only thing I could find was number 4 cylinder exhaust heat was about 100° cooler than the rest. I measured this using a IR thermometer pointed at the header. However I'm wondering if it's just because the coolant passage beside the #4 cylinder

dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Re: Possible Lean misfire help

Post by dluder »

Does anyone know what the ecu test for when doing injector test? Does it look for ground or complete circuit. I'm about to replace injector wiring from ecu and power wire from main relay? I'm not exactly sure where power comes from. Both ground and power test good but I gotta try something.

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Spunkster
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Re: Possible Lean misfire help

Post by Spunkster »

I believe it checks resistance.

dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Re: Possible Lean misfire help

Post by dluder »

Thanks for the reply. I didn't have time to replace the wires. However I checked continuity on the grounds and the was good. I did notice a .5 voltage drop from ecu to fuel injectors though. Im going to setup a power wire straight from the battery to fuel injectors to see if that'll fix the issue. Of course I won't leave it like that but I think that would be the easiest way to perform test. All the deadtimes are were they should be but if injectors is not getting same voltage then that maybe the issue. Idk will see.

dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Re: Possible Lean misfire help

Post by dluder »

Spunkster wrote:
Mon Feb 03, 2020 9:54 am
I believe it checks resistance.
Ive spent several hundred hours trying to narrow down issue and it is the hondata s300. We uploaded a tune on my tuners s300 board and it ran great. We then swapped it out with my s300 and it ran totally different. I've got a datalog showing the difference between the two. I'm not sure how to post them here but I could email them if you'd like. This was done on the same ecu and same laptop minutes apart. I sent in my s300 once at it was sent back and said it was ok. Also the red light will come on sometimes

dluder
Posts: 54
Joined: Mon Oct 22, 2018 6:08 pm

Re: Possible Lean misfire help

Post by dluder »

Spunkster wrote:
Mon Feb 03, 2020 9:54 am
I believe it checks resistance.
I sent an email to the support@hondata.com with all my info and datalogs showing the issue. The one labeled dusty datalog is my s300. You can look at graph and see the afr spikes

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