Why no high idle on the coldest day yet??

[mgray]

Cold weather has arrived here (-8c, 17F). Last night I had the truck plugged in for about 2.5 hours before start. Started fine, slightly high idle, slightly loud. But today after sitting 9hrs in the blowing cold UNPLUGGED, when it started, there was no high idle, just 650rpm, a little loud yes but not as loud as other "warmer" days (maybe around +8c, 46F) where I've seen it high idle at almost 1000rpm.

My question is that why does the high idle not happen when its really cold? I would assume that the colder it is, the more likely I am to get a high idle.

Also, it sounded like the batteries were struggling a bit, but it still turned over in a timely fashion. The batteries are only 6 months old(but they are made and I bought them in Mexico, covered in dust) and all my grounds are clean. Normal sounding? I'm running 15w40.

But more importantly, where is my high idle?

 

[NVW]

I dunno but could be a faulty temp sender. Leo

 

[just a number]

first make sure the solenoid is plugged in. I know simple but check. check to also make sure the temp sensor is plugged in(rear f RH head) and it's contacts are clean. did you also remember the push the throttle down with the keys on? the solenoid only holds it there, it doesn't open it.

 

[mgray]

first make sure the solenoid is plugged in. I know simple but check. check to also make sure the temp sensor is plugged in(rear f RH head) and it's contacts are clean. did you also remember the push the throttle down with the keys on? the solenoid only holds it there, it doesn't open it.

I've never touched the throttle on start....as I am electric injection I don't think that applies to me. I've had high idle before without having to touch the pedal, but thanks for the tip.

 

[just a number]

NVW might be onto something. check that temp sensor. the warmer it is the lower the resistance. also check to make sure it's getting a ground and a 5v signal to it. It's place to start

 

[mgray]

Ok, lets see here....you guys have mentioned two things; the coolant temp sensor and the soleniod right? Where exactly are they again?

I'll check the coolant temp sensor to see if there is 5v...but how do I confirm it's getting a ground?

Could the block heater have "boiled" the temp sensor?

Thanks again guys

 

[just a number]

to check for a ground, do a resistance check between a known good ground and the ground wire and see what you get. the block heater can't get hot enough to overheat the sensors. it's just designed to make it lukewarm at best.

 

[gmctd]

The solenoid is on "just a number's" GMC - to check it you would have to know where he lives, go there, then ask him to raise his hood - then you could check it

You will need to start with the connections and grounds on your EFI truck, as all idle conditions are PCM-controlled based on sensor inputs and battery voltage - you will need to check your Timing Stepper Motor for full travel, but at 155000mi, I'd say you are in dire need of timing chainset, injector pump, and injectors to restore normal operating functions - faulty sensors should DTC with check engine indication - so, after starting, press on the accel pedal, see if idle rpm increases and stays as PCM responds to resultant varying inputs - don't fergit to check your air filter for dirty, clogged, wet, also small furry critters assuming resident status in yer airbox, with resultant repasting on yer wiring harness(es)

 

[Turbine Doc]

first make sure the solenoid is plugged in. did you also remember the push the throttle down with the keys on? the solenoid only holds it there, it doesn't open it.

n/a on 6.5 DS-4 EFI engines, yes on mech IP

 

[docdray]

on my 94, mine went out and when replaced, made world of difference, even with 175,000 miles(changed chain at 177,000). ects(engine coolant temperature sensor)-top left on or near thermostat xover, black/yellow wire on mine. use ohm meter to test sensor itself-
degrees ohms
212 - 177
176 - 332
140 - 667
104 - 1459
86 - 2238
68 - 3520
50 - 5670
32 - 9420
14 - 16180
5 - 21450
-4 - 28680
-22 - 52700
-40 - 100700

quick test w/no ohm meter- disconnect sensor, engine should run high idle. short wiring connector, idle should drop to normal. ---test cnnector, 5v signal on yellow and ground on black.
=resistance high when cold, resistance low when hot. you can remove sensor and use a thermometer and ohm meter to test sensor eith pot of water on stove. My opinion, if you unplug sensor and idle goes up, the sensor ohms out high with engine warm-replace sensor, tighten new to 17 ft-lbs. mine went out at 167,000 miles.

wire in a high idle switch- it can be as simple as wiring a switch in to break this circuit.

 

[just a number]

yeah I realized after the fact about the year difference. 94 + up had the electronic mess to work with.

 

[mgray]

This was mentioned at the "other" place;

"Did you happen to run the glow plugs, turn the key off, and then back on again to run the glow plugs again? I tried that on mine once just for the hell of it (i dont have cold start problems) and it did not go into high idle that time."

That is what I did this time, although the first attempt was with my remote start that didn't crank long enough to turn over. So I had to recycle the key and glows for the second attempt.

Now that I think about it, every other time I didn't get a high idle I might have done the same thing before