The Camaro 1996 LT1 idle throws warm
08-17-2018, 08:45 AM
#1
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The Camaro 1996 LT1 idle throws warm
The cold engine will run idle, but with a warm engine the idling will sway in the range of 700-1400 rpm. When shifter is in position D or R it's better,N or P is bad.
Unless the load is running better. No air leaks,egr replaced, oxygen sensors replaced, plugs and plug wires exchanged, MAF, IAC and gas position sensor have been exchanged. Which can cause that problem. Kind of bad English, I live in Finland.
Ilkka
Unless the load is running better. No air leaks,egr replaced, oxygen sensors replaced, plugs and plug wires exchanged, MAF, IAC and gas position sensor have been exchanged. Which can cause that problem. Kind of bad English, I live in Finland.
Ilkka
08-17-2018, 10:58 AM
#2
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Location: Hell was full so they sent me to NJ
Posts: 70,647
Re: The Camaro 1996 LT1 idle throws warm
Is the engine modified from stock in any way?
Is the Optispark distributor the original unit, or has it been replaced? If replaced, what brand was used?
The stock idle speed programming for an automatic transmission in neutral, engine fully warmed up is 650 RPM. Typically, the PCM (computer) is able to control the idle within +/- 25 RPM using the IAC. The only way idle speed can increase is for more air to enter. Have you checked the throttle blades to see if they are moving when idle is surging? Hold the blade position quadrant fully closed against the stop.
With regard to the IAC, the PCM moves the IAC stepper motor pintle in "counts" to increase and decrease air flow. There is no feed back to the PCM regarding the actual IAC stepper motor position. Always possible the PCM signal is not getting to the IAC motor.
One way to diagnose idle speed problems is to observe how the PCM responds to the excessive idle speed - is it attempting to reduce the idle speed to the programmed value by reducing the IAC "counts"? That can be observed with a real time scanner, or using scanning software. There is a free download of OBD-2 scanner/data logging software available, written by one of the members on this site. It is sometimes difficult to get it running correctly with a European format PC operating system, but the author can step you through the process. Worth thinking about. You would have to buy a cable.
https://www.firebirdnation.com/forum...nner-software/
Is the Optispark distributor the original unit, or has it been replaced? If replaced, what brand was used?
The stock idle speed programming for an automatic transmission in neutral, engine fully warmed up is 650 RPM. Typically, the PCM (computer) is able to control the idle within +/- 25 RPM using the IAC. The only way idle speed can increase is for more air to enter. Have you checked the throttle blades to see if they are moving when idle is surging? Hold the blade position quadrant fully closed against the stop.
With regard to the IAC, the PCM moves the IAC stepper motor pintle in "counts" to increase and decrease air flow. There is no feed back to the PCM regarding the actual IAC stepper motor position. Always possible the PCM signal is not getting to the IAC motor.
One way to diagnose idle speed problems is to observe how the PCM responds to the excessive idle speed - is it attempting to reduce the idle speed to the programmed value by reducing the IAC "counts"? That can be observed with a real time scanner, or using scanning software. There is a free download of OBD-2 scanner/data logging software available, written by one of the members on this site. It is sometimes difficult to get it running correctly with a European format PC operating system, but the author can step you through the process. Worth thinking about. You would have to buy a cable.
https://www.firebirdnation.com/forum...nner-software/
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