High idle problem goes away when truck is in uphill position -18F; -28C°

[cauhcons]

Hi,
So last week it was freaking cold outside -18F; -28C° and the truck spill like 1 or 2 drop of coolant in my driveway, not really a big deal... but since this incident arrived the truck is idelling high like 2000rpm even when engine is warm, and at any speed, when i press the clutch while driving it never goes under 2000rpm.

So i observed that when i enter my driveway that got a slope, in a uphill position the problem immediately goes away. My thinking was that the coolant level was low and when in slope its return to normal, so i check the coolant level and its was like an inch down the correct cold level, so i refill the missing inch of coolant put the problem is still there...

do you think its because of air in coolant system, that i should get rid off?

if you have any idea of what it could be feel free to mention it.

Thanks a lot

 

[cauhcons]

update : no air in the system, i let it run for at least 15min and no air bubble.

the level of coolant in the rad was almost at the cap engine cold before i open it and let the truck run with my funnel to see if there was air.

 

[55trucker]

I'm surprised the PCM hasn't set a P0507 high idle code or possibly a P0505.

sure your check engine light is functioning?

I have to believe that there is a code set.

 

[cauhcons]

I'm surprised the PCM hasn't set a P0507 high idle code or possibly a P0505.

sure your check engine light is functioning?

I have to believe that there is a code set.

@55trucker, the cel is functioning correctly, despite i checked with a scanner and no code was stored.

also i realized that when i checked for air in the coolant system the thermostat never open @ 0C° 32F° the fan never stop and its enough to let the engine at his temperature set point without the need to circulate the coolant.(even at 3000rpm for like 15minutes)

so i am gonna re try the bleed procedure in a heated garage so the thermostat can open and may be let air get out of the system, But i still doubt that this is the cause of my problem, as i don't get overheating problem...

thanks

 

[55trucker]

You have a scanner, that's a good point, what is the * real time* temp of the engine that is displayed on the scanner screen from cold start *open loop* to hot *closed loop*?

You mention that the stat is *not* opening at 0C *ambient* and the fan is running constantly? ..well the fan will run all the time, it is just a thermal clutch fan, it never stops spinning, if the stat is not opening then I would imagine that the engine would overheat. If you're not seeing that sort of temp on the cluster temp gauge then use the scanner to read the engine temp.

 

[cauhcons]

You have a scanner, that's a good point, what is the * real time* temp of the engine that is displayed on the scanner screen from cold start *open loop* to hot *closed loop*?

You mention that the stat is *not* opening at 0C *ambient* and the fan is running constantly? ..well the fan will run all the time, it is just a thermal clutch fan, it never stops spinning, if the stat is not opening then I would imagine that the engine would overheat. If you're not that sort of temp on the cluster temp gauge then use the scanner to read the engine temp.

@55trucker, i'll check the real time temp tomorrow, from cold to hot and post it, if my scanner have the option, (i think yes like in data stream or something like that)

in my test the temp gauge on the cluster rise up to normal and stop there and i let the truck run for at least 40min and at the end i throttle it to 3000rpm for 15min and the lower hose of the rad was still cold and the upper was darn hot, but the coolant in the funnel was not that hot, just like a coffee lol

thanks for you help,

 

[55trucker]

Keep in mind in this *cold snap* weather that we're both getting the engine system cooling will see a considerable temp difference in the two rad hoses. The upper will be hot and the lower will get cold seeing the rad is passing much cooler air thru it than what is seen in the summer months.

pick yourself up a digital thermal temp gun.....they're useful, Flat Tire (that's spelled Canadian Tire) often has a special price on them for approx $25 on sale.

http://www.canadiantire.ca/en/pdp/mastercraft-digital-temperature-reader-0574554p.html

 

[cauhcons]

You have a scanner, that's a good point, what is the * real time* temp of the engine that is displayed on the scanner screen from cold start *open loop* to hot *closed loop*?

You mention that the stat is *not* opening at 0C *ambient* and the fan is running constantly? ..well the fan will run all the time, it is just a thermal clutch fan, it never stops spinning, if the stat is not opening then I would imagine that the engine would overheat. If you're not seeing that sort of temp on the cluster temp gauge then use the scanner to read the engine temp.

I dont have temp of engine on my scanner, instead i have coolant temp. So cold start -1C and it never exceeded hot 88C

That mean the stat open correctly, you are right the difference in the two rad hose temp is explain by the so cold air run through the rad and boost up cooling efficiency.

No air in the cooling system, correct level of coolant in rad and in the tank, So it cannot be the cause of the high idle.

i forget to mention, that the problem (2000rpm idle) never appear at the beginning of the ride but more often after like 5 or 10 min, when it happen it never stop until the truck is put in a up hill position, when it append i climb a snow bank and it immediately disappear and sometime reappear after like 10min and sometime not...

Is there an other fluid that can cause and high idle?

thanks

 

[55trucker]

If you plug in the scanner & start the engine stone cold and let the vehicle stand motionless in a level position......at what point (engine/coolant temp) as being read from the scanner screen does this anomaly begin to occur? Does it start while the management system is still open loop or does it begin after the system goes closed loop?

 

[cauhcons]

If you plug in the scanner & start the engine stone cold and let the vehicle stand motionless in a level position......at what point (engine/coolant temp) as being read from the scanner screen does this anomaly begin to occur? Does it start while the management system is still open loop or does it begin after the system goes closed loop?

Hi, Steve

Happy New Year to you!

sorry for the delay, it seem that the problem only occur when its -5°C or less, because before today it never showed up again...

so the high idle appear at a coolant temp of 40°C right before the arrow start touch the first line of the temp gauge on the cluster and it continue even when its stabilized to 88°C.

So the high idle showed up in the open loop and persist even in close loop.

its still disappear a second after I uphill the truck.

Thank you!!!

 

[Mightyfordranger]

Well check the o2 sensors see if one has a crack, and check the connection of tps and the other vaccum lines in the maf.

sounds like when it gets super cold that possibly a rubber hose get shrunk, and starts sucking in the outside cold air.

If it keeps doing this try grabbing a can of starting fluid and giving it a spray here and there around the vaccum lines. If it picks up in rpm then you at least know it has a leak and it's that general area where you sprayed.

But just from reading through this thread I'd say you either have a vaccum leak somewhere, that the hose moves when you pull the truck up on a hill.

Or you have water in something that shouldn't be there and when it got cold the first time it froze and started problems.

Sent from my SM-S903VL using Tapatalk

 

[cauhcons]

Well check the o2 sensors see if one has a crack, and check the connection of tps and the other vaccum lines in the maf.

sounds like when it gets super cold that possibly a rubber hose get shrunk, and starts sucking in the outside cold air.

If it keeps doing this try grabbing a can of starting fluid and giving it a spray here and there around the vaccum lines. If it picks up in rpm then you at least know it has a leak and it's that general area where you sprayed.

But just from reading through this thread I'd say you either have a vaccum leak somewhere, that the hose moves when you pull the truck up on a hill.

Or you have water in something that shouldn't be there and when it got cold the first time it froze and started problems.

Sent from my SM-S903VL using Tapatalk

Update

first @Mightyfordranger & @55trucker thanks for your Help

So i checked all vacuum line, i even check the vacuum reservoir and everything is fine, the blend door is working properly as well for the recirculating door.

TPS connection look mint no corrosion at all same for the MAF
For now i havent clean the MAF as i dont think its the problem, but i'll do it soon

O2 sensor seems visually ok

I notice since then, that i was wrong thinking that a up hill position solve my problem, in reality its when the truck is at 0mph with a little kick on the gas pedal the RPM immediately run from 2000 to 800/900, if i did the same when the truck is running at more then 2mph its not working, i really have to stop the truck and then it work. It came back right after i move the truck, and never stop until complete stop and a little kick on the gas pedal...

i will try to run with my scanner plug to see if the TPS is acting weird and i'll post back the result

meanwhile do you have an idea of what it could be with this new info.

thanks!!!