Cold Idle Control issues.
 

Now that the winter is here my cold idle control is in the dumps.

This is an issue that presented itself a few years ago when my alternator was not charging well at idle, or whenever there is an accessory left on that drops battery voltage.

Problem is that whenever there is a decent draw (or low voltage) on the charging system the "automatic high idle" will not work. If I leave all accessories off (heater, lights, radio) it will work normally.

Tonight I payed around with it a bit........I went in and setup the Cold Idle Multiplier and Cold Idle Control to always be in "high idle". This worked great until I flipped on the lights or heater, then right back down to normal idle speed.

The system voltage (according to the Scangauge) is right at 14.2-14.4v.

I am starting to get a bit irritated with this as the truck really does not warm up to well at base idle, and I am not willing to turn off the heater.....lol.


Any ideas why this is, or what parameter to adjust to relax this a bit?

Hmmm. No problems here. Last night after reading this post I went outside and started the truck. It was 20 degrees and I instantly turned on my HVAC blower to high, turned on my lights, and waited.

20 seconds later (glow plugs still on as well as all loads), the truck was in it's high idle mode.

Ya, I know it is strange. Guess I could always just put the chip back in, or that box, but I would rather find the issue then cover it up.

I might hook up the BOB and see what voltage actually is at the PCM during this condition.

So what your saying is any time there is any kind of current draw, the truck wont go into high idle? You alt at one time didnt charge well, but now it looks to be charging ok?

I've had issues in the past with the race car, when the alt would start to give out, it would tend to scramble the firmware in the EFI computer. I always knew when I was getting ready to lose an alternator because I'd get a bunch of noise on the sensors..

The only conditions that I know of that have to be met for your truck to go into high idle is, has to be in park, the throttle pos. sensor has to be within a certain range, the brake light switch, and engine oil temp cant be above a certain temp. So I'd look at what the sensors are doing, see if your getting and kind of noise that might not allow it to go into high idle..

Whats the engine oil temp when it's doing all of this?

Thats really all I can think of.. It's been in the low teens here in the mornings, and my truck has gone into high idle everytime without an issue. Thats with the heater going full bore, stereo system going, and typically with the lights on.

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.:hmmm:

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

Well I thought I had the issue resolved until temps dropped to -40 for the past week or so - and it stopped working again.

Using the Scangauge I monitored the IAT and it was reading 500* (which I now believe is an issue with the Scangauge), so I disconnected the sensor and it defaulted to 68 and the high idle seemed to work normally - when the engine was cold.

Today I spent a bit of time playing with it and was pretty successful controlling the idle with the sensor disconnected, once it warmed up I lost all control of the high idle.

I tried changing the default to 0*F , setting the Cold Idle control to be always on - regardless of temp - and it still wont work when the engine is warm.

When the sensor is disconnected does it substitute a different temp sensor?

As a last ditch effort I plugged the sensor back in, and still no high idle function.

I think I'd make sure your issues isn't the sensor. What makes you think it's something with the Scangauge and not the sensor? I had a bad EOT sensor, or bad wires to it, awhile back, once I hooked a scanner to it it came obvious when it was reading 4 degrees on a warm engine. I'd make sure that sensor is reading correctly before you spend a bunch more time trying to adjust the tuning for it.

Reason I dont think it is the sensor is because when it is unplugged the default to 68*(which it displays) - I went in an changed the default - and whenever it is set lower than 0*F it displays 500*.

This leads me to believe the Scangauge is not set up to read below 0*.

That makes sense. Do you have AE where you can verify this?

I do have a Genisis and Verus I can use to verify, just haven't felt the need to yet.

I about got this one figured out;), but there is still a strange issue. When engine is cold, the idle will raise up to what it should - then suddenly drop back down to base idle. It will continue to do this for a few minutes, then it might decide to work and stay up on the high idle, or might just stay at base idle.

Also, my Autostart is messing with this somehow. This evening I started the truck after dinner - went out about 10 minutes later and it was still at base idle speed. Stuck my key in and turned to the "run" position and after a few seconds it ramped right up to where I had set it...lol.

I will be playing around with it some more in the AM.

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

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... :hmmm:

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?)

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?