Brief Idle Hang Revival

[Solid Red 98]

I was having the all too familiar idle hang issue on my 98 and I tried these three operations that seem to point toward a cure:

1) Clean the IAC (idle air control) motor on the side of the right intake--mine was sticky

2) replace short, heat relaxed/hardened vacuum lines (forward between the intake) This alone lowered my idle to ultra-lope satisfaction

3) and this seems to be a big one make sure your A/C is functional and at nominal pressure.

The pressure switch that activates the fan through the ecu may be signaling some sort of transient 'idle up' command due to low or no pressure in the A/C system. Low A/C charge might be worse than no charge, due to the effects of rising engine compartment temperatures on the pressurized gas; raising it just enough to trip the pressure switch. My car would only hang when fairly hot after spirited and hill driving. In addition, my coolant temperatures are fluctuating less as well, as the fan is managing radiator temps a bit better.

Perhaps some of you car-brain-logic gurus can enhance or debunk this part of my theory, but between these three little operations, I have turned the corner on idle hang for over a thousand miles and counting. (this is not an April fools, by the way)

 

[eucharistos]

good info

as you titled "....revival" i take it you read the other threads, added your thread to the others here: http://forums.viperclub.org/rt-10-gts-discussions/634078-high-idle-help.html#post2826514

 

[Solid Red 98]

Thanks for transferring that, I zoned when posting.

 

[Jack B]

I was having the all too familiar idle hang issue on my 98 and I tried these three operations that seem to point toward a cure:

1) Clean the IAC (idle air control) motor on the side of the right intake--mine was sticky

2) replace short, heat relaxed/hardened vacuum lines (forward between the intake) This alone lowered my idle to ultra-lope satisfaction

3) and this seems to be a big one make sure your A/C is functional and at nominal pressure.

The pressure switch that activates the fan through the ecu may be signaling some sort of transient 'idle up' command due to low or no pressure in the A/C system. Low A/C charge might be worse than no charge, due to the effects of rising engine compartment temperatures on the pressurized gas; raising it just enough to trip the pressure switch. My car would only hang when fairly hot after spirited and hill driving. In addition, my coolant temperatures are fluctuating less as well, as the fan is managing radiator temps a bit better.

Perhaps some of you car-brain-logic gurus can enhance or debunk this part of my theory, but between these three little operations, I have turned the corner on idle hang for over a thousand miles and counting. (this is not an April fools, by the way)

I haven't used air or had a charge in my system for over four years with no idle hang. When i had the idle-hang it was due to the loss of the ground wire for the O2 sensor circuits. That wire originates in the harness near cylinder #1 and runs to a bolt (ground) on the ac compressor. If you have worked on the compressor there is a chance that wire was torn off.