Rocker Idle?
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Joined: Mar 2007
Posts: 3,706
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From: Woodstock, Ont , Can
Your tuner screwed up. Reving cold start is normal and it drops rpm as it heats up. A hot start will only be very slight increase for only about a second before dropping to normal rpm. There is a setting for iac home position which provides air for starting when throttle is closed. Then there's a setting for normal idle whether cold or hot in the ecm. What you are hearing in rpms is the time lag it takes for the ecm to take control so it runs on home iac position. My guess is it shouldn't be more that two seconds. It needs to be dropped to the point that hot start position of the iac is close to ecm setting. I just went through this with my Tmax and quite sure the HD ecm works the same way. Doc on this forum would know for sure, but I think my explanation is close enough to explain why it behaves that way.
950 is a good rpm to idle at. Have mine set at 940 pushing 12 psi on hot oil. No problem oiling with that pressure. Now some only idle at 3 psi at 1000 rpm. These are not candidates for dropping the idle. See where I'm going with this? Even on a high pressure engine you can only go so low and the charging system will not keep up.
Ron
950 is a good rpm to idle at. Have mine set at 940 pushing 12 psi on hot oil. No problem oiling with that pressure. Now some only idle at 3 psi at 1000 rpm. These are not candidates for dropping the idle. See where I'm going with this? Even on a high pressure engine you can only go so low and the charging system will not keep up.
Ron
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Cruiser
Joined: Jul 2008
Posts: 216
Likes: 0
From: Rohnert Park
Your tuner screwed up. Reving cold start is normal and it drops rpm as it heats up. A hot start will only be very slight increase for only about a second before dropping to normal rpm. There is a setting for iac home position which provides air for starting when throttle is closed. Then there's a setting for normal idle whether cold or hot in the ecm. What you are hearing in rpms is the time lag it takes for the ecm to take control so it runs on home iac position. My guess is it shouldn't be more that two seconds. It needs to be dropped to the point that hot start position of the iac is close to ecm setting. I just went through this with my Tmax and quite sure the HD ecm works the same way. Doc on this forum would know for sure, but I think my explanation is close enough to explain why it behaves that way.
950 is a good rpm to idle at. Have mine set at 940 pushing 12 psi on hot oil. No problem oiling with that pressure. Now some only idle at 3 psi at 1000 rpm. These are not candidates for dropping the idle. See where I'm going with this? Even on a high pressure engine you can only go so low and the charging system will not keep up.
Ron
950 is a good rpm to idle at. Have mine set at 940 pushing 12 psi on hot oil. No problem oiling with that pressure. Now some only idle at 3 psi at 1000 rpm. These are not candidates for dropping the idle. See where I'm going with this? Even on a high pressure engine you can only go so low and the charging system will not keep up.
Ron
Could you please tell me what ECM stands for and IAC?
Thanks again.
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stevefxdi
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Nov 21, 2011 04:00 PM
