Cold Idle Control issues.

[Power Hungry]

Originally Posted by 907dave

Yeah, seems to be working fine, no noise (AC volts) in the charging system either.

Since posting this I had gone through all my battery/ alt connections and cleaned everything, regardless of how it looked.

Since then it has seemed to be working normally.

There must be an undefined table that has some bearing on this...............ohhh Bill!!!!

I'm looking into this. There's only one problem. I'm having a little trouble generating the -40º temps out here.

The issue definitely seems related to your IAT as this has significant bearing on the Cold Idle control. Case in point... I was in a truck on a roughly 15º day and the engine was sufficiently warm because I was inside tuning it. After a short bit, the idle ramped up even though EOT was well over 100º. This indicates that the idle strategy does look at IAT as well as EOT to control high idle.

Now the big question is, where does this function go awry? Is the PCM actually miscalculating the IAT output or is the scan-tool miscalculating the PID data and handling it as an unsigned value instead of a signed value? These are question I don't yet have an answer to since my truck is in GA and I'm in FL, but I will certainly be happy to investigate this and see what's up.

Stick around...

[GTS]

I think if there is question at to weather the sensor is reading correctly that would be the first thing I would want to verify so you're not chasing your tail trying to figure it out.

As for the autostart I think I may have an answer for you. I have remote start on my truck as well and though it is a '96 I do have an AIC on it. When I remote start it the wires are tagged that are needed to start the truck but not all accessory wires have power to them. My AIC is apparently one of the wires that doesn't have power to it as it will not idle up without the key in it. I've been going to find the wires needed to fix this but just haven't gotten around to it yet. So you may want to get a wire schematic and trace the wires for what sensors are needed to activate the high idle (e-brake circuit?)

[907DAVE]

Okay, my idle was working perfectly for about a week or so, then the issues came back with a vengeance. The issue is consistent when using the auto-start, so I decided to go after this first.

Just so everyone knows, I installed the auto-start when I first purchased the truck and has worked normal up until this year.

I check voltage drop through the Auto-start for all my ignition wires, and it was .2v, not great, but could be worse. The voltage would stay around 13.7 volts with all the accessories on. Now the real kicker is when the Auto-start times out, and the turbo timer kicks in the idle works normally. The timer is tied into the exact same wires but is only dropping .1v.

Here's a video I took just for giggles.......



Since this still appears to be a voltage issue, and the only time it has ever done this in the past is with low battery's........Does the PCM read system voltage in A/D counts?