Desired Idle higher than base setting
Desired Idle higher than base setting I have been working on tuning my 5.3 turbo in my 66 Chevelle. I am using HPT with a 2004 blue/green ecm from a blazer. I am running DBC and a t56 for the trans.
The issue I am having is the idle will not settle down into the base setting I have in the tune 850. Instead the ECM is commanding a desired idle around 900 then the desired idle will creep back up to about 1000.
I can force the car to idle at 850 using the vehicle control functions.
I attached copies of my current tune and a cold start log.
Any help would be appreciated. Thanks
The issue I am having is the idle will not settle down into the base setting I have in the tune 850. Instead the ECM is commanding a desired idle around 900 then the desired idle will creep back up to about 1000.
I can force the car to idle at 850 using the vehicle control functions.
I attached copies of my current tune and a cold start log.
Any help would be appreciated. Thanks
Wannafbody yes it is DBC.
minitrker I will try resetting it back to stock. I have been messing with that table using chopperdoc's guide. I will go back and verify the log math is correct.
Thanks
minitrker I will try resetting it back to stock. I have been messing with that table using chopperdoc's guide. I will go back and verify the log math is correct.
Thanks
I tried resetting the IAC Steps and the base running airflow tables closer to stock. This caused some starting issues but after adjusting the base running airflow up a bit to get a better startup and idle again. On the first startup the ecm pretty much commands 1000 rpm off the bat and never changes. On restart the ecm will start then slowly run down to the commanded idle rpm. after a few seconds it will then start adding to the idle rpm until it gets back to 1000.
As far as I can tell the throttle blade is retuning fine ( I actually tried a different throttle as well.) I have the throttle set so at idle the IAC is around 60 counts but when the idle is high it is closer to 100-120 counts.
As far as I can tell the throttle blade is retuning fine ( I actually tried a different throttle as well.) I have the throttle set so at idle the IAC is around 60 counts but when the idle is high it is closer to 100-120 counts.
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Joined: Aug 2010
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From: Ann Arbor, MI
But doesn't the OP's mention that the IAC is going up from 60 at 850 RPM to 120 at 1000 RPM indicate that the PCM is commanding the higher IAC and hence idle speed, and that the throttle body is therefore likely fine?
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Verdad Gallardo I'm not sure. My tuning didn't change but after I switched from a Nick Williams to a billet Holley my idle drops faster. It used to hang for maybe 4-5 seconds before dropping. Now I'd guess 2 seconds or so. Same sensor.
Correct it is definitely being commanded to idle higher. On the log I attached you can see I am logging the RPM and the Commanded RPM.
I just cant figure out why the ecm is commanding the rpm 100 or so more than what it's set at.
At the end of the day its not a huge issue but it would be nice to know why.
I just cant figure out why the ecm is commanding the rpm 100 or so more than what it's set at.
At the end of the day its not a huge issue but it would be nice to know why.
Correct it is definitely being commanded to idle higher. On the log I attached you can see I am logging the RPM and the Commanded RPM.
I just cant figure out why the ecm is commanding the rpm 100 or so more than what it's set at.
At the end of the day its not a huge issue but it would be nice to know why.
I just cant figure out why the ecm is commanding the rpm 100 or so more than what it's set at.
At the end of the day its not a huge issue but it would be nice to know why.
I appreciate everyone's help here.
I have tried fudging the number lower but it does occasionally go to the number I set. When that happens the motor will stall as it doesnt like to idle below 700ish. Of course that may be able to be tuned out but with the BTR stg2 turbo cam I think the motor just seems more steady around 850-900rpm.
NicD you are correct I started with the auto file. Are you suggesting starting over with a completely different OS or would a segment swap from a manual trans be ok? The reason I just switched it to manual from auto is I had done that in the past with other swaps and older trans setups without issue. Those swaps were way more basic than this one has been with the e85, 3 bar and all that goes with it. If you are suggesting starting with a completely different OS I will probably take the time to scale the tune to get more control of the timing under boost.
I have tried fudging the number lower but it does occasionally go to the number I set. When that happens the motor will stall as it doesnt like to idle below 700ish. Of course that may be able to be tuned out but with the BTR stg2 turbo cam I think the motor just seems more steady around 850-900rpm.
NicD you are correct I started with the auto file. Are you suggesting starting over with a completely different OS or would a segment swap from a manual trans be ok? The reason I just switched it to manual from auto is I had done that in the past with other swaps and older trans setups without issue. Those swaps were way more basic than this one has been with the e85, 3 bar and all that goes with it. If you are suggesting starting with a completely different OS I will probably take the time to scale the tune to get more control of the timing under boost.
I would like to give it a crack, ive personally never dealt with this ECM in particular but here we go.
as mentioned, not sure why its requesting 100-200 RPM more than desired but im sure we can figure out the adjustment to that. I see your VE table has been worked on a bit so thats good.
Not sure if the P59 will like this but can you try adding the following to your table,
Idle Air Control Position
Idle Air Control Desired Position
Idle Desired Airflow
Idle Startup Airflow
Idle Base Gear Airflow
Idle Base Sum Airflow
Idle Base PN Airflow
Idle Adapt (STIT)
LTIT Gear/ACoff
LTIT PN/ACoff
Timing Advance (SAE)
Idle Advance
Idle AC Airflow
Idle Cracker Airflow
Idle Follower Airflow
as mentioned, not sure why its requesting 100-200 RPM more than desired but im sure we can figure out the adjustment to that. I see your VE table has been worked on a bit so thats good.
Not sure if the P59 will like this but can you try adding the following to your table,
Idle Air Control Position
Idle Air Control Desired Position
Idle Desired Airflow
Idle Startup Airflow
Idle Base Gear Airflow
Idle Base Sum Airflow
Idle Base PN Airflow
Idle Adapt (STIT)
LTIT Gear/ACoff
LTIT PN/ACoff
Timing Advance (SAE)
Idle Advance
Idle AC Airflow
Idle Cracker Airflow
Idle Follower Airflow
Also did a quick search on p59 not requesting demanded rpm idle and apparently its a known issue, it tends to command its own desired RPM at times.
Solution , write entire with another OS
Solution , write entire with another OS
Sorry I have not updated this thread in a bit. I have been working on getting my C10-L33 swap up and running so I haven't messed too much with the Chevelle lately other than driving it.
I did try a segment swap from a manual with no luck on the commanded idle.
I will add those to my table and log and see if it shows anything.
I did see a thread about having to change the OS but was hoping to avoid that if at all possible but it may have to happen. I have a couple other Blue/Green ECM's but I will have to check and see if they will work with the 3 Bar/flex fuel/DBC setup I have in the car. If they are the correct OS I may try one just to see what happens.
Thanks
I did try a segment swap from a manual with no luck on the commanded idle.
I will add those to my table and log and see if it shows anything.
I did see a thread about having to change the OS but was hoping to avoid that if at all possible but it may have to happen. I have a couple other Blue/Green ECM's but I will have to check and see if they will work with the 3 Bar/flex fuel/DBC setup I have in the car. If they are the correct OS I may try one just to see what happens.
Thanks
TECH Resident
Joined: Oct 2006
Posts: 993
Likes: 173
From: Euless, TX
P01/P59 can both increase idle at times as needed for cooling (elevated temps) or battery charging. If the alternator is not PCM controlled, you need to disable the "F" terminal in the system matrix. If the PCM is programmed to control the alternator duty cycle to the regulator and it goes above a commanded 80% DC it can increase the RPM up to 150 rpm for example.