Question about idling problems

[juntjoo]

What is happening exactly in the engine when, as I can describe it, while the car is idling it it seems to skip a beat or hesitate and letting off the pedal the engine struggles to catch itself from the drop in rpm's. It's obviously weaker but i'm wondering if it's not getting enough air(rich?) or the other way around or what. I'm just trying to understand how this works. BTW currently this happens mostly when the engine is under extra load from the AC or even the little rear defrost button. Really?

 

[juntjoo]

And as I said I think, I already tested with a new IAC, so i'm wondering what one of you was saying about giving the ECU a chance to learn the IAC. If that could be the issue, since interestingly when I put both a used and a brand new one in, it seemed to idle correctly for maybe no more than a minute, then reverted back, how does the ECU know when a new one is installed and how should I "reset" the partnership, if you will? <-- 1st time I've ever written "if you will".

 

[impossible]

Hey,

(That´s the strict way)
if you changed the ISC you should disconnect your battery for a few minutes.
(Best way: Disconnect it while you are changing the ISC)
After that, run the engine ~10 min without any appliance in idle speed.
That´s necessary to train the ECU to the new ISC.

setting the idle speed:

- Engine is warm
- Without any appliance

---> steps of the ISC should be between 8-12
---> the idlee speed should be at about 850 rpm (just turn the screw as long as you reach the mark)

You are only able to see the steps with a data logger.

A damaged ISC could have caused damages to your ECU, especially to the power driver. That means a brand new ISC wouldn´t help.

Idle issues are one of the main problems at all

Regards

 

[juntjoo]

Hey,

(That´s the strict way)
if you changed the ISC you should disconnect your battery for a few minutes.
(Best way: Disconnect it while you are changing the ISC)
After that, run the engine ~10 min without any appliance in idle speed.
That´s necessary to train the ECU to the new ISC.

setting the idle speed:

- Engine is warm
- Without any appliance

---> steps of the ISC should be between 8-12
---> the idlee speed should be at about 850 rpm (just turn the screw as long as you reach the mark)

You are only able to see the steps with a data logger.

A damaged ISC could have caused damages to your ECU, especially to the power driver. That means a brand new ISC wouldn´t help.

Idle issues are one of the main problems at all

Regards

thanks. Any recommendations on a data logger for this car? Never shopped for such a thing. And since i'm not changing ISC's now, then I just need to basically reset the ECU then correct, which would be by disconnecting the battery for a bit correct? Thanks!

 

[NHerron]

Great info impossible

 

[juntjoo]

Well as far as the BISS, I set it now for about 600rpm because by the time it's hot it increases 300rpm. So cold starts require manual idle assistance aka my foot. No change with ECU reset. Btw.