Cold Idle Control issues.

[Colt]

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.

[907DAVE]

Originally Posted by Colt

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?

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!!!!

[907DAVE]

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.

[GTS]

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.

[907DAVE]

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*.

[GTS]

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

[907DAVE]

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.

[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...