High unstable Idle since Cold temps set in

fishrod

fishrod

New member
In the past few days the temp has dropped from around 0C to between -10 and -15 overnight, and its expected to get colder. Ive noticed that when I start the truck up its revving much higher than it usually does and its also not very steady.

It usually (cold engine in warm temps) will sit spot on 1400 rpms until it warms a bit and then it idles at about 800 rpms when warm.

Now its shooting straight up to 1800 - 2200 and kinda goes up and down between those values for a good 5 mins or so until the temp gauge starts to move off cold.

What would be some things to check or suggest that my mechanic checks? This never happened last winter, though last winter I was parking in a heater garage half the time and the winter was much milder.

Thanks!
 
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Temp sensor has gone wonkey... That would be my first guess... Maybe a tiny vacuum leak that`s agitated with the denser cold air...:cheers:
 
Could also be as simple as low coolant level, an easy place to start.
It could also be because it's just so cold.
 
Thanks for the replies, ill try checking some of those things first.

Yeah -15 aint that bad, it was actually -22 last night when I finished work (I found out tonight when I got to work what the low was last night) Gettin down there. You def notice the difference between -5/-10 to -20ish

Warmer weather is on the way thankfully.
 
fishrod said:
Thanks for the replies, ill try checking some of those things first.

Yeah -15 aint that bad, it was actually -22 last night when I finished work (I found out tonight when I got to work what the low was last night) Gettin down there. You def notice the difference between -5/-10 to -20ish

Warmer weather is on the way thankfully.
Click to expand...

Send the Snow and Cold over here! I want to use the sled this year!!:lol:
 
fourwd1 said:
Could also be as simple as low coolant level, an easy place to start.
It could also be because it's just so cold.
Click to expand...


Ill give fourwd1 1 point out of a possible 2. Coolant wasnt really low, well define low, I put about 1/4 of a litre in the radiator and a little in the overflow. Radiator level I could see the coolant, it was above the fins, but about 3/4 of an inch from "full full".

It didnt idle as high this time, still bounced around a little, but not as much the past few days. Then again it was only -10 or something tonight so probably "because it's just so cold".
 
fishrod said:
Ill give fourwd1 1 point out of a possible 2. Coolant wasnt really low, well define low, I put about 1/4 of a litre in the radiator and a little in the overflow. Radiator level I could see the coolant, it was above the fins, but about 3/4 of an inch from "full full".

It didnt idle as high this time, still bounced around a little, but not as much the past few days. Then again it was only -10 or something tonight so probably "because it's just so cold".
Click to expand...

Not sure if it impacts the idle but if you keep the overflow topped up then the rad itself should be "full full". Did you have any fluid in the overflow when your rad was low? You may need a rad cap (cheap fix.)
 
I had that happen to me once it ended up being an air lock in the throttle body so no coolant was getting through
 
Kmvreter said:
Not sure if it impacts the idle but if you keep the overflow topped up then the rad itself should be "full full". Did you have any fluid in the overflow when your rad was low? You may need a rad cap (cheap fix.)
Click to expand...


hmm, its wierd, ill top up the coolant and the overflow. Within a few days the overflow will be bone dry (dunno where it goes). But after a few weeks the radiator level is still pretty much full. I dont think there is any leak in the system and I dont think its the cap, I got a new radiator cap about 12 months ago. I guess it could have gone bad already.

Maybe this time the coolant got a little low and was causing it to act up. Temps have warmed up recently and the issue has gone away. Probably still leaning towards that IACV so might try and give that a clean.

Anyone know of any threads on here (or elsewhere) on instructions on cleaning up the IACV? FSM doesnt have it listed, at least not the one I have.
 
Issue is back

Normally it would idle around 1000-1200 but now that the temp had gone down to -15 to -20 in the morning it now revs/idles higher at 2000+!

After a few mins it drops back to 1500 or so.

Just a little concerned as I dont like the engine revving at 2000+ revs when its stone cold.

Any more ideas what it could be? Coolant temp sensor? IACV?
 
So your problem from Nov 2010 is back a year later?!
If you are topping off the rad and the overflow and then days later the overflow is empty, the overflow bottle could have a leak or the cooling system does and is sucking it out of the overflow.
How about doing a pressure/leakdown test on the cooling system.
 
I just dont see how the coolant level would affect this. Its gotta be a sensor or something since it ONLY happens when the temps drop.

I gave up on finding the leaking coolant. Its not really an issue, it just seems to suck the overflow bottle down to the MIN level and then I can go months in the summer without having to top up the main reservoir.

I think I reserched this a bit more last winter and the IACV valve/sensor came up?

Perhaps one of the O2 sensors might be causing this as well?

I dunno by the time I got anywhere the temperature warmed up and it went away again so I just left it. We had a very mild winter last year but this year I am a bit further north so its going to be a bit more of an issue.
 
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