Idle Speed?
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Elder User
Joined: Aug 2003
Posts: 568
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From: Kansas
Idle Speed?
This is my first winter for a Diesel and would like to know why, when you start it cold, it idles at about 900rpm for a couple of minutes and then all of a sudden, it jumps to 1200rpms. It will come back down to normal idle if you apply the brakes. This sounds kinda dumb but anyway is this normal for a COLD weather start?
Postmaster
Joined: Feb 2002
Posts: 2,773
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From: Bonney Lake, WA
I think it has to do with the glow plug cycle. When you first turn the key, prior to starting the truck, the glow plugs begin to cycle. Once you've started the truck, the glow plugs stay activated for another 1-2 minutes. Once the voltmeter recovers, and begins to show a charging condition, the glow plugs have shut off. Does that timing coincide with when the idle speed rises? It might very well be built into the programming of the pcm for the idle speed to stay low until the glow plugs have finished cycling, then increase the rpm to help the truck warm up sooner.
Senior User
Joined: Dec 2002
Posts: 135
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From: North Idaho
I've seen a factory idle speed controller on ambulance packages to maintain alternator output, and they shut off with brake application. They were mounted under center dash.
Do you have one of these?
Do you have one of these?
Senior User
Joined: Aug 2002
Posts: 274
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From: Taunton, MA
99+ PSDs will do this, high idle. After startup the glowplugs keep cycling as Quad said, but also if the PCM sees 40 or maybe 32 deg (not sure but cold!) or colder, after 120 seconds it will raise the rpms to high idle to warm up more quickly. You can over ride it by hitting the brake or accel petal.
Nelson
Nelson
Tuned
Joined: May 2003
Posts: 303
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From: Kentucky
Mine will do this if it is below 32 degs, I have not noticed it doing it in any warmer weather. I think it is the PCM and it knows when to fast idle the truck for cold weather. It will not do it after the truck has warmed after the first time unless it is allowd to cool completely.
Posting Guru
Joined: Apr 2003
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From: Fairbanks Alaska
Normal, the comp monitors the temp and if it is cold idles up the engine to raise the combustion temp. It knows that cold running is bad.
I hear the newer PSD's will do it if you sit to long at a light and its really cold.
My Cummins does it also. Plus I know that my Cummins monitors the intake temp and will turn the intake air heater on to compensate (Cummins use a heater screen instead of glow plugs)
I hear the newer PSD's will do it if you sit to long at a light and its really cold.
My Cummins does it also. Plus I know that my Cummins monitors the intake temp and will turn the intake air heater on to compensate (Cummins use a heater screen instead of glow plugs)
Senior User
Joined: Aug 2002
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From: Taunton, MA
Yup, the PCM uses the EOT Sensor (engine oil temp) and the IAT Sensor (intake air temp) - the one that plugs into the side of the intake airbox- to determine if it's cold enough to kick up to high idle and/or activate the EBV.
Nelson
Nelson
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Cold Ambient Protection
My 2003 F250 will increase its engine RPM's from its normal 650, to 1000 if it sits long enough in cold weather, normally it will high idle after about 15 mins of sitting. Some say that the parking brake must be set for it to start this process, but mine will start without it set. This is process called the Cold Ambient Protection, its a feature thats not well advertised. It also has a Exhaust Backpressure Valve (EBV) behind the turbo that closes and puts a load on the PSD when it is cold, this will usually make the PSD idle around 820 RPM's when in effect. It makes a vacuume cleaner like noise, and itll cycle on and off based on the temp readings. The both work well to keep the $10,000 baby inder the hood warm.
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Post Fiend
Joined: Jul 2005
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From: 21791
when the ambient temperature is below 37*F and the Engine oil temperature is below 140*F, the engine will respond with higher idling (up to 1200rpm) after about a minute or so of idling. this is followed by the activation of the EBPV closing making the horribly-awesome hissing sound
Senior User
Joined: Nov 2004
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From: Central Wyoming
Originally Posted by strokin_it7.3
when the ambient temperature is below 37*F and the Engine oil temperature is below 140*F, the engine will respond with higher idling (up to 1200rpm) after about a minute or so of idling. this is followed by the activation of the EBPV closing making the horribly-awesome hissing sound
Senior User
Joined: Oct 2004
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From: South Dakota
The Exhaust Back-Pressure sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a linear analog voltage signal that indicates pressure. The Exhaust Back-Pressure sensor measures the pressure in the RH exhaust manifold. This sensor is used in conjunction with the exhaust back-pressure regulator to form a closed loop exhaust back-pressure control system.
The exhaust back-pressure is controlled by the PCM to provide more heat to the coolant for cab heating when ambient air temperature is below 7°C (45°F) and engine oil temperature is below 75°C (167°F) during low load, low speed operating conditions.
The exhaust back-pressure is controlled by the PCM to provide more heat to the coolant for cab heating when ambient air temperature is below 7°C (45°F) and engine oil temperature is below 75°C (167°F) during low load, low speed operating conditions.
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Joined: Jan 2003
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From: 3rd Rock
Originally Posted by pray for surf
My 2003 F250 will increase its engine RPM's from its normal 650, to 1000 if it sits long enough in cold weather, normally it will high idle after about 15 mins of sitting. Some say that the parking brake must be set for it to start this process, but mine will start without it set. This is process called the Cold Ambient Protection, its a feature thats not well advertised. It also has a Exhaust Backpressure Valve (EBV) behind the turbo that closes and puts a load on the PSD when it is cold, this will usually make the PSD idle around 820 RPM's when in effect. It makes a vacuume cleaner like noise, and itll cycle on and off based on the temp readings. The both work well to keep the $10,000 baby inder the hood warm.
…..See you on the boards.
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