How to keep idle from hunting after driving for a while
02-20-2014, 02:58 PM
#1
How to keep idle from hunting after driving for a while Asked once before & even posted tune. I have turned off learning by maxing condition where learning would take place while driving. Not ECT related either.
After driving for a while idle will bounce up & down, never constant unless I turn the car off to re-set the PCM. Have simplified everything that may cause this (as a condition of driving) & have not been able to keep it from happening. Also, remember dampened the IAC valve control/conditions without any luck. Then changed it back to a stock setting w/ no luck. Although, I do expect that it is the IAC valve parameters that cause the problem.
98 PCM, EFI Live
After driving for a while idle will bounce up & down, never constant unless I turn the car off to re-set the PCM. Have simplified everything that may cause this (as a condition of driving) & have not been able to keep it from happening. Also, remember dampened the IAC valve control/conditions without any luck. Then changed it back to a stock setting w/ no luck. Although, I do expect that it is the IAC valve parameters that cause the problem.
98 PCM, EFI Live
02-21-2014, 03:09 PM
#4
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May just be a marginally stabe RPM control loop, and
you end up on the wrong side of stable for whatever
reason after driving.
If you're convinced that idle-range fueling is good
and timing is adequate, maybe you want to play with
the idle RPM loop P, I, D coefficients. I did this, cut
and try, and it seemed to help some. I'd try raising
the D value incrementally and see if that cuts out
the yo-yo action.
But before that you might use bidirectional controls
and lock a roughly-right IAC position and see whether
it's stable or unstable. There are kinds of VE table errors
(MAP-axis slope) that can give you a fuel surge and
then the IAC is left chasing a bouncing ball (good luck).
you end up on the wrong side of stable for whatever
reason after driving.
If you're convinced that idle-range fueling is good
and timing is adequate, maybe you want to play with
the idle RPM loop P, I, D coefficients. I did this, cut
and try, and it seemed to help some. I'd try raising
the D value incrementally and see if that cuts out
the yo-yo action.
But before that you might use bidirectional controls
and lock a roughly-right IAC position and see whether
it's stable or unstable. There are kinds of VE table errors
(MAP-axis slope) that can give you a fuel surge and
then the IAC is left chasing a bouncing ball (good luck).
02-21-2014, 05:09 PM
#5
May just be a marginally stabe RPM control loop, and
you end up on the wrong side of stable for whatever
reason after driving.
If you're convinced that idle-range fueling is good
and timing is adequate, maybe you want to play with
the idle RPM loop P, I, D coefficients. I did this, cut
and try, and it seemed to help some. I'd try raising
the D value incrementally and see if that cuts out
the yo-yo action.
But before that you might use bidirectional controls
and lock a roughly-right IAC position and see whether
it's stable or unstable. There are kinds of VE table errors
(MAP-axis slope) that can give you a fuel surge and
then the IAC is left chasing a bouncing ball (good luck).
you end up on the wrong side of stable for whatever
reason after driving.
If you're convinced that idle-range fueling is good
and timing is adequate, maybe you want to play with
the idle RPM loop P, I, D coefficients. I did this, cut
and try, and it seemed to help some. I'd try raising
the D value incrementally and see if that cuts out
the yo-yo action.
But before that you might use bidirectional controls
and lock a roughly-right IAC position and see whether
it's stable or unstable. There are kinds of VE table errors
(MAP-axis slope) that can give you a fuel surge and
then the IAC is left chasing a bouncing ball (good luck).
Thanks for the reply. I should have mentioned that it's OL MAF. Although, your MAP fuel surge comments makes me wonder if the issue could be in the OL fuel table. Will also look into the RPM loop variables.
02-21-2014, 05:52 PM
#6
Could it be that I have no airflow correction between ECT & IAT? Noticed that I set the threshold to 200 RPM which means there is never any correction relative to airflow from 0-150 g/s. At first I thought maybe the values used were too low from 0-150 g/s, (which may also be the case since they are much lower than on a stock 02 engine), then noticed there is no correction @ all because of the 200 RPM threshold.
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02-23-2014, 11:16 AM
#10
A combination of things. Am gonna pretty much leave it alone. Other than the hunting idle, (only after driving once or twice) I really like the way it runs. Will be @ least 6 more weeks of storage before it's driven. So, we can't test multiple changes to the tune right now. Was hoping for a simple quick fix.
Thank-you all for the input.
02-24-2014, 01:06 PM
#11
Should note that I am gonna put the manual calibration file into the tune. Did not realize that using the auto trans calibration file can cause issues on a manual car. Did transfer the manual files onto the automatic calibration tune file, but did not realize that we had to begin by using the manual calibration file itself in order to avoid idle issues.
What's the easy way to do it? I have the manual tune file in the same OS. It appears that I will have to copy & paste every part of the current tune (w/ automatic calibration) onto the manual calibration tune file? Is there an easier way?
What's the easy way to do it? I have the manual tune file in the same OS. It appears that I will have to copy & paste every part of the current tune (w/ automatic calibration) onto the manual calibration tune file? Is there an easier way?
02-24-2014, 04:03 PM
#12
Open the manual tune, then click load alternate file for comparison and open the auto tune. Click the Red arrow like this <--> and it will show you all the differences between the two tunes. You can then select any table from the list and click update and it will the value from your original tune into the manual.
Its not going to be a simple fix unfortunately. Once on table is off its starts a snowball effect and you start having to change more and more tables to get it to act right. You can try your current idle stuff in the manual tune and see if it makes it any better but I suspect it wont fix 100% of your idle issues but its a start in the right direction.
If you dont have a manual tune let me know and I'll send you a one.
Its not going to be a simple fix unfortunately. Once on table is off its starts a snowball effect and you start having to change more and more tables to get it to act right. You can try your current idle stuff in the manual tune and see if it makes it any better but I suspect it wont fix 100% of your idle issues but its a start in the right direction.
If you dont have a manual tune let me know and I'll send you a one.
02-24-2014, 08:52 PM
#13
Open the manual tune, then click load alternate file for comparison and open the auto tune. Click the Red arrow like this <--> and it will show you all the differences between the two tunes. You can then select any table from the list and click update and it will the value from your original tune into the manual.
Thanks, that looks much easier.
