imstimpy

Some odd behavior cropped up while I was at the track a couple weekends ago. While waiting to go out for the session the car began to choke, nearly stall, recover, choke, repeat all in a slow manner. I could mitigate the behavior by pressing the gas pedal slightly, though it felt a bit sluggish and difficult to set RPM. The car felt fine while driving the prior track day (and the logs all showed nothing wrong), and it felt fine that afternoon despite the stalling.

Yesterday, I found some time to troubleshoot. I started the car and it idled fine until it reached near operating temperature. At that point the problem presented itself again. I reset the ECU and the problem was immediately present with the warm engine. I had a chance to log the behavior with Hondata and I cannot see anything abnormal except the AF slowly oscillating between 19:1 and 10:1 and the STRIM attempting to correct with 9% to -22%; the stalling occurs when it is super rich.

I had the chance to inspect the plugs (replaced a few months ago) and they all look near new save for a small amount of white speckling. I did a compression test and found ~220psi on 3 and 4 and ~215 psi on 1 and 2. I inspected my low load fuel map and couldn't see any holes; adjusting fueling couldn't tune out the issue.

I'll switch to logging with HDS to see if any additional monitors shed light on the situation. Thus far, the MIL has not illuminated though I did forget to check for pending codes (which I'll do later).

The car is a 2008 with ~39,000 miles. It has an intake, headers, HFC, cat-back, Hondata flash (my own tune), and an AP1 flywheel. I did a clutch job about 600 track miles ago, and had the intake manifold off prior to that, so I'll double-check all electrical connections and ground.

Any thoughts?

kukudm

Give this thread a read and see if your issue is similar to it. Pay attention to point #2 in the first post.

https://www.s2ki.com/forums/s2000-un...ilure-1171212/

imstimpy

Thanks for the suggestion.

Awhile back while my clutch wasn't fully disengaging (this was a new behavior after the car sitting for nearly a year). Upon pulling the transmission I found the input spline lube had turned to sludge and the splines rusted. A new ACT HD pressure plate, stock clutch disk, and new lube and the problem entirely went away.

I don't think it is crank walk but I will pull the VTEC solenoid and look for metal shavings. I will also scrutinize the idle behavior with the clutch in and out. At the track the issues were with the clutch in, when the thrust bearing would create an issue. However while the car was on the lift for diagnosis the clutch was out as I wasn't even in the car.

imstimpy

I doubt it is the thrust bearing. After a long negative terminal pull, the car started and idled for 10+ min without issue. It wasn't until I shut it off and did a hot restart that the problem came back, manifesting as 19:1 AFR and misfires across all cylinders. This appears to electrical, rather than mechanical.

While I can't conclusively diagnose what, exactly, is the issue, I can say that something changes after the first restart. Since the ECU tracks things like idle re-learn, hot starts, start temperature, something is triggering it to go wonky. I am beginning to suspect Hondata/Flashpro, either a corrupted calibration or a problem with the live tables. I recently flashed back to a calibration I had from a year ago, also disabling live tables, and numerous hot starts did not exhibit the problem. I need to spend more time going through a full relearn, then iterating on various calibrations and live table states before I can confidently say what is going on.

Car Analogy

Maybe a vacuum leak?

You had IM off recently, maybe its come loose? Check bolt torque.

imstimpy

I can certainly look but MAP is showing 200-300mbar as expected.

imstimpy

I've concluded this is a bug in the implementation of Hondata's Live Tuning code. With the feature disabled, the car works as expected.

imstimpy

Nope, I was wrong! Disabling Live Tuning appears to be coincidence. What gets the girl all wanting to stall? Driving her brains out at the track. So the problem came back again, this time after about 4 hours of track time yesterday. Again, no codes. Though this time I did notice -18% LTRIM.

I flashed back to the map that worked last time but to no avail. It wasn't until I held RPM at 4500, in neutral, for 20-30 seconds was it then able to hold idle once more. Though I have been touching up my tune in post-track logs, I never really gave the tune the proper attention after swapping my exhaust manifold. I'm confident in the fueling at WOT; the rest, not so much.

My conclusion at this point is the plugs became partially fouled from excess fuel due to a hole somewhere in my fuel tables. Idling/revving in neutral is close enough in fueling that the plugs eventually cleaned themselves and allowed the fuel to burn properly at idle.

stevejin

Bumping up an old thread since I’ve experiencing the same issue.

For me, it only happens when I’m at the track.

OP, have you figured out what the culprit was? Or have you found a solution to this problem?

alSpeed2k

I experienced a similar issue while on track in early September as well. Nothing since, but I think mine was due to an intake issue as my air filter was quite dirty.