High Idle Speed
Thread Starter
Instructor
Joined: Aug 2003
Posts: 172
Likes: 0
High Idle Speed
I'm having difficulty getting a new engine to maintain the SET idle speed. Have adjusted the new TPS and IACV per the Chevy manual w/ out success. The engine still moves back up to about 1200 rpm. Could this be the effect of an improperly burned chip? All the easy things check out ok. I have an old Hypertech II chip rthat could be substituted for the newly burned one. Any thoughts on what the 400 ci., 219 cammed engine would react like? or better yet - possible answers to the underlying problem? Thanks, Jack
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Have you adjusted the minimum air? Maybe the throttle blades are open too far. What IS the idle speed in the new chip? You could try the Hypertech or the stock chip, for comparison. Is the CTS connected and working properly?
RACE ON!!!
RACE ON!!!
Thread Starter
Instructor
Joined: Aug 2003
Posts: 172
Likes: 0
CFI-EFI & Scorp
CFI-EFI and Scorp:
Will check the throttle blades for complete closing when "OFF". Don't know what the re-programmed chip was made to idle at (if this is a function of the chip??????). Don't recognize the term CST. What is it?
I don't have the scan tool(s) to check the "count" and am trying to get an idle that remains near 900 rpm. Something continues to force the idle up from there to the 1200 rpm range. AM SHOWING 17.5 VACUUM AT 900 RPM and no apparent leaks.
Any further ideas? Thanks for your responses thus far, Jack
Will check the throttle blades for complete closing when "OFF". Don't know what the re-programmed chip was made to idle at (if this is a function of the chip??????). Don't recognize the term CST. What is it?
I don't have the scan tool(s) to check the "count" and am trying to get an idle that remains near 900 rpm. Something continues to force the idle up from there to the 1200 rpm range. AM SHOWING 17.5 VACUUM AT 900 RPM and no apparent leaks.
Any further ideas? Thanks for your responses thus far, Jack
Team Owner
Joined: Mar 2000
Posts: 83,381
Likes: 87
From: Boston, MA
CTS = Coldstart Thermo Switch
On 85-88 it monitors the temp of the coolant at startup and injects a mist of fuel into the intake manifold for a short length of time to help start a cold car.
Its going to be hard to get a good idle on a modified car without a scan tool.
On 85-88 it monitors the temp of the coolant at startup and injects a mist of fuel into the intake manifold for a short length of time to help start a cold car.
Its going to be hard to get a good idle on a modified car without a scan tool.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by bigjack
CFI-EFI and Scorp:
Will check the throttle blades for complete closing when "OFF". Don't know what the re-programmed chip was made to idle at (if this is a function of the chip??????). Don't recognize the term CST. What is it?
Will check the throttle blades for complete closing when "OFF". Don't know what the re-programmed chip was made to idle at (if this is a function of the chip??????). Don't recognize the term CST. What is it?
Originally Posted by CFI-EFI
Is the CTS connected and working properly?
RACE ON!!!
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Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Without a scan tool it's difficult to set minimum idle. Try it again though relying on the dash and set it right around 450 rpms. Reset the TPS to .54 volts. Then depress the accelerator slightly and start it. Let it run for 10 seconds then off 5 seconds. When you restart it, idle should be correct.
Last edited by SunCr; Nov 1, 2004 at 05:23 PM.
