Idle help please
05-05-2008, 05:45 PM
#1
Staging Lane
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Idle help please 03 GMC 5.3 228/228 cam Truck has ETC
Using the search and tips i found the truck finaly does idle on it's own but I am trying to iron out the last problems I seem to be going no where. The tips found so far seem related to cable TB with a IAC.
Cold starts are still bad. need throttle to keep it running.
One warm it idles OK, but transition back to idle after throttle it wants to drop RPM to stall and has to hunt for while until is steadys out.
What is the best direction here?
More timing at the lower RPMs?
Or more air flow? If more air, which table?
Help Please!
Thanks in advance.
Steve
Using the search and tips i found the truck finaly does idle on it's own but I am trying to iron out the last problems I seem to be going no where. The tips found so far seem related to cable TB with a IAC.
Cold starts are still bad. need throttle to keep it running.
One warm it idles OK, but transition back to idle after throttle it wants to drop RPM to stall and has to hunt for while until is steadys out.
What is the best direction here?
More timing at the lower RPMs?
Or more air flow? If more air, which table?
Help Please!
Thanks in advance.
Steve
05-09-2008, 02:56 AM
#3
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try increasing the idle airflow table. Its under Engine > Idle > Idle airflow > Base running airflow. You could try upping the entire table maybe 10%, fine tune from there and see how that helps. You'll just have to experiment to some extent. To much will probably make it surge, too little it will want to stall. You may also have to play around with the eq table for open loop(cold start). Engine > Fuel Control > OL & CL > Eq ratio. That controls the air/fuel ratio for when the motor is in open loop. I havnt messed with that too much so i cant help you there...
Id start with increasing the idle airflow and also upping the rpms to 700-800 or where ever the motor seems happy first as that should fix 95% of your idling problem.
When in scanner mode you can increase the spark advance by using the the plus feature in the VCM controls under fuel and spark. This will add whatever timing you have entered in the vcm controls to the timing table in the pcm. For example if your stock idle timing table has 22º degrees max putting 4º in the vcm controls plus box would give you 26º total. If you find it helps your idle you can then change the vcm idle spark tables. I dont know if increasing timing at idle can cause any potential problems or not but i guess as long as it isnt knocking it shouldnt cause any problems. changing the timing for idle wont fix any major idling problems though. Try playing with that while the car is idling and see if it helps. The spark control at idle is only used for fine adjustments as it can react a lot faster to idle speed changes then the IAC or the ETC. I guess you can think of it as helping to smooth the idle from what i understand.
Id start with increasing the idle airflow and also upping the rpms to 700-800 or where ever the motor seems happy first as that should fix 95% of your idling problem.
When in scanner mode you can increase the spark advance by using the the plus feature in the VCM controls under fuel and spark. This will add whatever timing you have entered in the vcm controls to the timing table in the pcm. For example if your stock idle timing table has 22º degrees max putting 4º in the vcm controls plus box would give you 26º total. If you find it helps your idle you can then change the vcm idle spark tables. I dont know if increasing timing at idle can cause any potential problems or not but i guess as long as it isnt knocking it shouldnt cause any problems. changing the timing for idle wont fix any major idling problems though. Try playing with that while the car is idling and see if it helps. The spark control at idle is only used for fine adjustments as it can react a lot faster to idle speed changes then the IAC or the ETC. I guess you can think of it as helping to smooth the idle from what i understand.
Last edited by got-a-ls1; 05-11-2008 at 09:54 AM.
05-11-2008, 11:36 AM
#6
Even better is using a cfg file setup for idle airflow instead of guessing on the RAF. You start the car cold with this cfg, turn off the fans with the VCM controls, don't turn on the air and then just log till it reaches 216 degrees. Turn it off and copy the desired airflow table right onto the RAF. Here:
http://www.hptuners.com/forum/showthread.php?t=8191
I just did 3 passes over the last 3 days for my new 90mm setup and it's idling fantastic. Also most cams idle well with 22-26 degrees of timing. Also make sure when idling your IAC counts are between 60-80 hot, makes a huge difference.
http://www.hptuners.com/forum/showthread.php?t=8191
I just did 3 passes over the last 3 days for my new 90mm setup and it's idling fantastic. Also most cams idle well with 22-26 degrees of timing. Also make sure when idling your IAC counts are between 60-80 hot, makes a huge difference.