Idle issue still going on.......

is there a cam?? chip tune in the ecm??

With the idle set so far above the commanded idle, the EEC can get confused when trying to get it lower, esp as it transitions from a roll to a stop.

HISSIN50 said:

With the idle set so far above the commanded idle, the EEC can get confused when trying to get it lower, esp as it transitions from a roll to a stop.

Click to expand...

yea that had happened to me after getting a tune, i wanted to lower the idle a tad.

Go back the "Surging Idle Checklist” and do the set the base idle procedure. If the engine will not idle at 600 RPM with the IAC disconnected and the SPOUT removed, you have mechanical problems like vacuum leaks.

Try the base idle and plug the IAC in without the SPOUT.
If the surge goes away, you have a problem in the PIP circuit.

If the engine still surges, then the problem is in the IAC.

IAC doesn't work: look for +12 volts at the IAC red wire. Then check for continuity between the white/lt blue wire and pin 21 on the computer. The IAC connector contacts will sometimes corrode and make the IAC not work. The red wire on the IAC is always hot with the engine in run mode. The computer provides a ground for the current for the IAC. It switches the ground on and off, making a square wave with a varying duty cycle. A normal square wave would be on for 50% of the time and off for 50% of the time. When the idle speed is low, the duty cycle increases more than 50% to open the IAC more. When the engine speed is high, it decreases the duty cycle to less than 50% to close the IAC. This is why a DC voltage measurement isn't very helpful in diagnosing IAC problems. Once you get past the 12 volts on the red wire, everything else is a pulse that needs an oscilloscope to measure it correctly



Probable cause:
Disconnect the computer main connector and the IAB connector. Measure the resistance between pin 21 on the computer connector and ground. My guess is that you will find less than 200 Ohms, which is a short that would keep the IAB fully turned on.

An old-fashioned dwell meter can be used to check the change: I haven’t tried it personally, but it should work. In theory, it should read ½ scale of whatever range you set it on with a 50% duty cycle. An Oscilloscope is even better if you can find someone who has one and will help.