random negative timing causing car to stumble

[hexdmy]

I had someone contact me who has a KA24DE-T with a strange problem. The car has a rom tune already in it, using a PLMS board, and the calibration is based off of a 54C00 bin. I found that the O2 sensor wire had been repaired poorly, and the shielding was shorting to the sensor wire. I fixed that, and we took the car for a drive. At first, the car ran ok, but after about ten minuets, the car started stumbling, almost as if it was getting too much fuel on tip in. The stumble got worse, to the point that the car did not want to accelerate. I was not logging, but I was streaming, and watching all gauges, I noticed that the ignition timing was showing negative timing past -10 when the car would stumble. Tried unplugging the knock sensor without much change. I read out the calibration, and both timing maps were set to the same. I'm wondering what could be causing the timing to go negative, searching around, I found a thread online where someone ran into the same issue, but there was no follow up. Has anyone seen this before ? Any input is appreciated.

[Matt]

The only time I've seen timing go negative was with HCR32 ECU having one the timing maps set to FFs due to using an image from earlier model (04U01 eg) and moving on to later model (11U00 eg) which uses two timing maps

In this case you have confirmed that both timing maps are the same

What I'm confused with is why 54C00 maps (SR20) were used with a KA24DE ECU

Compare the current maps against KA24DE factory and see if there is anything which looks incorrect in the comparison

[hexdmy]

Hi Matt, thanks for the input. I'm guessing they used the SR20DET calibration because it was based off of an turbo engine, but those SR engines had distributors like the KA. Not sure if that is an advantage over the KA calibration though. Can you verify that the lowest timing values I should see, would be the ones in the low octane map? If so, I think I might try un-selecting the knock flag in the calibration to see if that makes any difference.

[Matt]

Knock timing map shows 3 degree absolute lowest. Typically these areas arent reached so about 15 degrees off idle timing

Check TPS idle becomes unlit also on acceleration

43 43 41 39 37 35 34 33 30 27 24 22 20 18 18 18
43 43 41 39 37 35 34 33 30 27 24 22 20 18 18 18
43 43 41 39 37 35 34 32 29 26 24 22 20 18 16 16
43 43 41 39 37 35 34 32 29 26 24 22 20 18 16 16
43 43 42 41 39 37 36 35 33 32 30 27 24 20 16 16
43 43 43 42 41 39 38 37 34 31 28 26 24 20 16 16
43 43 43 41 39 37 36 35 33 31 29 26 23 19 16 16
43 43 43 42 41 38 36 34 33 32 31 29 27 24 22 22
46 46 46 45 42 40 38 36 34 32 30 29 28 27 27 27
46 46 46 45 43 40 38 36 34 31 28 25 23 23 23 23
45 45 45 45 42 39 36 33 30 27 24 21 18 16 16 16
43 43 43 43 41 39 36 32 29 26 23 20 17 15 15 15
35 35 35 35 35 32 27 24 21 18 16 14 12 9 9 9
25 25 25 25 25 25 23 21 18 16 14 12 10 7 7 7
20 20 20 20 18 16 14 12 10 8 6 4 4 4 4 4
15 15 15 15 14 12 10 8 7 6 5 4 3 3 3 3

[hexdmy]

Sorry, not sure what you mean by this, can you clarify ?

Check TPS idle becomes unlit also on acceleration

[Matt]

On the consult display (one with the speedo and RPM needles) there is an indicator 'TPS idle'

This should only be lit when accelerator released. Just check that also

[hexdmy]

Driving around in this car again today, the same timing retard / stumble behavior is there after driving for about ten minuets, but it's not as bad as the last time. I did datalog this time, and sure enough, you can see that the timing just drops by 15 degrees or so, I do not see anything that stands out in the log that would be triggering this problem. The closed throttle flag is clearing anytime the throttle is open. You can see this problem clearly around the 04:20.9 mark in the log.

I'm going to socket another ecu and give it a try, hopefully this is a hardware issue.

[Matt]

Log doesnt have 'TP' ticked so cant follow the load in playback

It is normal for S13 KA24DE to have between 0 and 5 degrees BDTC timing at 85 degC coolant temp seen earlier in the log

However at the point you mention we see timing going -2 BDTC and TPS shows throttle at this time so that is definitely unusual. would like to see the BIN file being used at the moment with this.

[hexdmy]

Regarding TP, it was not available in streaming mode, as in, it did not show up as a selectable PID.

I did not want to post this tune file up, so I emailed it to you.

[Matt]

No probs. Emailed response back. Would suggest starting with standard file and copying necessary maps over. That is a straight RNN14 SR20 file which shouldnt be loaded as is into S13 KA24DE ECU