Stumped @ idle fluctuations
#1
Stumped @ idle fluctuations
Evenings are starting to get a bit chilly now, so I logged my car warming up after I started it after class. As you can see the idle is reasonably stable until about ~1600 rows into the log, where it starts getting big fluctuations out of nowhere.
Anyone have any ideas of what's going on? It's almost like the ECU suddenly starts looking up a different ISCV table after a little while.
The fluctuations start almost exactly 2 minutes after the car was started.
Anyone have any ideas of what's going on? It's almost like the ECU suddenly starts looking up a different ISCV table after a little while.
The fluctuations start almost exactly 2 minutes after the car was started.
#2
EvoM Guru
iTrader: (1)
I get the same thing but my hardware is significantly modified. I've been reading the disassembly thread but some of the tables do no seem to have the desired effect.
Have you referenced that thread lately?
What cams and throttle body?
Have you referenced that thread lately?
What cams and throttle body?
Last edited by 211Ratsbud; Oct 9, 2013 at 04:27 AM.
#7
Evolved Member
iTrader: (6)
What can cause this? Let's say that the physical ISCV is not broken or sticking..
Knowing that you're already pretty much good with ISCV stuff, I'm gonna share the ideas that comes on my mind, just in case that it would help you:
To me, it seems like a PID with the setpoint too far from process value. (in this case, target idle too far from actual idle). This cause the controller to overshoot up and down and get out of control.
Keep updating I wanna know the outcome of your research.
Knowing that you're already pretty much good with ISCV stuff, I'm gonna share the ideas that comes on my mind, just in case that it would help you:
To me, it seems like a PID with the setpoint too far from process value. (in this case, target idle too far from actual idle). This cause the controller to overshoot up and down and get out of control.
- It seems to happen when the ECU starts interpolating with the 122F value, in whatever table is causing that. It seems to taper off where the ECU starts to interpolate with the 170F value. So maybe trying to see if you could set another demand value for 122F at main demand tables (or another one)
- Too agressive idle error table ?
- I'd try to reset the BISS screw at any other opening to see if it will get the ECU to keep better control of the setpoint vs process value at this new BISS flow.
- Last but not least, getting ALL the ISCV tables and target RPM tables to stock and resetting the BISS could bring you back closer to a good idle tune. Last year I happened to tweak too much tables ending up all f*c* up, having no choice to restart at the beginning.
Keep updating I wanna know the outcome of your research.
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#15
Nothing major yet, I've been too busy with work to have time to tinker around with it very much. I did notice a boost leak last weekend which I fixed, but it didn't have a very big effect on improving idle.
I'll update this thread when I've had a chance to try some of the things suggested here
I'll update this thread when I've had a chance to try some of the things suggested here