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Infamous AP2 06+ Hesitation Update

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Infamous AP2 06+ Hesitation Update

 
Old 09-07-2018, 05:45 AM
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Thumbs up Infamous AP2 06+ Hesitation Update

The "slight" hesitation on the low-end of the power band has been a major problem with the 06' + AP2DBW S2000s. I probably read hundreds of the comments about the problem with one previous owner and S2Ki member almost giving slight depression because the he gave up and sold the car due to this problem.
I have been working on this issue as well for 1 year and I can say that I am getting closer. I might honestly think the last bit of hesitation is the tune provided by Honda which the fuel tip-in has a error and causes issues. I did not come with that conclusion myself but that was the conclusion of the S2Ki members working on this issue for years.

What I did at first:
  • Valve Adjustment
  • Spark Plugs
  • MAP Sensors
  • New DMW sensor (The one in front of the brake master cylinder in the engine bay)
  • Reset ECU
  • Cleaned Throttle body
  • Fuel Cleaner
  • New Serpentine Belt
  • Inspect Injector lines
  • Replaced Coil Packs
What made the most difference?
  • Reseting the ECU makes the car run really good for a few days but after it "learns" the issue comes back
  • Coil Packs- The issue is like 90% gone. It is every now and than there but the car runs noticeably better
What I am planning to do next if it comes back or just to get that last 10%
  • Primary O2 Sensor
  • New Throttle Body because the motor inside can be having issues
  • Hondata Tune
I hope this helps and after the coil packs it is so much better.

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Old 09-07-2018, 06:23 AM
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The "slight" hesitation on the low-end of the power band has been a major problem with the 06' + AP2DBW S2000s.
Never had it before the car was FlashPro tuned. Don't have it now. But I've been driving DBW cars for a dozen or more years every day.

-- Chuck
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Old 09-07-2018, 07:17 AM
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I've come to the conclusion it's the tune. Not just the fueling, but more the throttle plate mapping.

The stock throttle plate mapping is very non linear. Which explains why dbw S feel much less responsive than cable throttle S. Its not so much a time lag between pedal action and throttle plate response, but rather the mapping of how much pedal results in how much throttle plate at what vehicle speed and what engine rpm. The stock mapping is truely awful. Its like its for a minivan or something. Its all damped out, so the throttle response is deadened.

There are two tables. One uses vehicle speed and pedal position to map to an 'index' value. This index is then used along with engine rpm to map to throttle plate opening.

I suspect that with the stock mappings in these tables, at just the right conditions, speed, rpm, pedal, the throttle plate opening gets momentarily reduced. That as you increase vehicle speed, and hit a different index on the first table, its possible to land at a spot on the second table that has a lower throttle opening. Then as speed or pedal or rpm change further, you land on another spot with a wider opening and the car seems to respond normally again.

I have been experimenting with the throttle mapping, making it more linear, more one-to-one, but a little more damped at lower speed and lower rpm for easier take off, stop n go and parking lot stuff, but more like a proper sportscar everywhere else. Not to address the hesitation, but rather the lack of throttle response.

I have completely discarded the stock throttle plate mapping, and created my own. Most of my changes are around eliminating most of the effect of vehicle speed from mapping. Now, at a given pedal position, the throttle plate position is largely unaffected by how fast the car is traveling. That, and making the rpm based table more linear. Push the pedal 10%, throttle opens 10% more.

The results have been fantastic. The car is so much more responsive. The throttle response now is unreal. Also, so far I haven't had any of the dbw hesitations.

If I have time, I may do some experimenting with taking the way the stock mapping does things, and go overboard farther in that direction, to see if it makes the hesitation more prevalent. That would give evidence that its the weird mapping that is the cause of the hesitation.
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Old 09-07-2018, 12:08 PM
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I appreciate this write-up. I've recently switched from an 03 to an 06 and have been slightly annoyed by the hesitation. I've done a valve adjustment and have new spark plugs that haven't been put in yet. My car runs great aside from the slight hesitation. The good news is that in aggressive driving/autocross, I have not noticed any of this bad behavior. There are subtle things that are not as good/responsive as the 03 in terms of driving feel but the 06 is objectively somewhat faster. I'd love to be able to try an 06+ car with a lighter flywheel, tune, throttle mapping, and CDV removal. I'm hoping to reach that combination eventually and that it will keep all the pros of the 06+ and gain the positive aspects that I miss about the 03 drivetrain. I don't care that my tach won't say 9k, I just want the snappier revving, snappier shifting, and quick, linear response. Chassis-wise, I'd also like the quicker steering rack back. Those are the subjective things that I miss about the AP1.
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Old 09-07-2018, 04:49 PM
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You just described my S. I'm still working on the CR steering rack to get the quicker ratio. But so far I have:

Swaybars and springs from older model S, to give more rearward bias (for more dynamic fun on the street, not for lap times)

Flashpro with Gernby tune, hfc that allows tune to lower vtec, higher redline, and custom linear throttle map

Lightweight flywheel (11 lbs), cdv removed, heavy ss shift knob

Trying to combine the best attributes of ap1 and ap2 (my version of the best). I pretty happy with the results so far!
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Old 09-07-2018, 05:46 PM
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You forgot a simple one, adjust throttle cable.
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Old 09-07-2018, 05:48 PM
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I had this problem recently on my '06... hesitation or stumble at low to medium throttle while cruising or lightly accelerating... particularly bad when the AC was on or in the damp. I reset the ECU, cleaned the throttle body, cleaned the MAP sensor connector, inspected the plugs, and performed a valve adjustment... none of which solved the problem. For me, the solution came from a new Accelerator Pedal Position Sensor. Cost me about $200, but only 10 minutes to install. I believe the old APPS sensor was giving the ECU an erratic output at low throttle. There's a night and day improvement in how the vehicle responds to low to midrange throttle input... first drive after the new sensor was installed and I accidentally chirped the tires in my driveway.
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Old 09-08-2018, 06:44 AM
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For emphasis as this seems a logical solution. Appears to be part No.37971-PZX-003. Thanks for posting it!
For me, the solution came from a new Accelerator Pedal Position Sensor. Cost me about $200, but only 10 minutes to install. I believe the old APPS sensor was giving the ECU an erratic output at low throttle. There's a night and day improvement in how the vehicle responds to low to midrange throttle input... first drive after the new sensor was installed and I accidentally chirped the tires in my driveway.
-- Chuck

Last edited by Chuck S; 09-08-2018 at 06:47 AM.
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Old 09-08-2018, 07:01 AM
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I have an 2006 with Gernby tune and use his throttle mapping which really helps the pedal feel at low speed. I have experienced hesitation a few times but its rare. Thanks for posting about the accelerator pedal position sensor dadadaveed. If hesitation was more prevalent in my S I would probably buy one.
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Old 09-08-2018, 10:41 AM
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Wondering if its possible to clean and reuse the pedal position sensor?

If its a potentiometer type sensor, dirty contacts would explain why it goes bad with these symptoms. If you can get in tbere with contact cleaner spray, it might resolve without having to buy a $200 part.

I will investigate further...
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