Idle feels like slight misfire but no CEL

[saintjah]

- serial number of your K-Pro4
- 4.2.3.0
- ECU part number 37820 PRB A05
- KManager version 4.2.3
- Modifications: Comptech supercharger, ID1000 injectors, CT exhaust, Flexfuel,
- Science of Speed 2009
- a specific description of the problem:

Car seems to have a slight cough or choke at idle, intermittent. Almost seems like a misfire but there are no CELs present and the car runs fine other than that. The Kpro4 is also tuned on E85 and the problem at idle does not exist when ethanol content is over 70% idle is perfect. Seems to only do this on octane.

[saintjah]

2003 Honda S2000

[Spunkster]

You have not included a datalog showing the issue.

[saintjah]

it gets perfect if I fatten it up to 12.5/1 but isnt that too rich? The data logs dont show any abnormalities and the slight idle misfire doesnt throw any cel.

[saintjah]

heres a data log

[Spunkster]

Have you tried changing the AF ratio at idle when this happens to see if that makes it go away either making it richer or leaner?

[saintjah]

Around 12.5 it will smooth out, is that not too rich for idle?

[Spunkster]

IS this when it is both hot and cold?

[saintjah]

Only when warm, once it gets up to temp 180f~ is when it starts.

[saintjah]

Im pretty sure it is not the ECU, I have just recently purchased a NEW Kpro4 from a licensed vendor and it does the exact same thing.

[Spunkster]

Have you tried replacing your spark plugs?

[saintjah]

Yes, they are new. I also have an AEM infinity and it idles perfectly on it. Coils, plugs etc.. all new

[Spunkster]

Then it sounds like it may just be a tuning issue if it only does it when hot, and another system works ok as well. Have you discussed the issue with your tuner?

[saintjah]

He took the same route and said to check the ECU. New has to be fine.

Is 12.5/1 at idle too much? If I set it to that it is fine and no misfires

[Hondata]

The KPro is not the ECU. It still could be the ECU.
I'd lower the overrun cutoff pressures and try changing the idle ignition parameters, but the main thing that stands out is that the injector dead times are very low. ID1000s should be around 1.2 ms at 14V.
The other issue common with idle mixture is any very slight exhaust leak will give the o2 sensor a false reading.