Is this right or wrong?
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Is this right or wrong?
2005, F-450, 6.0 PSD. Should my engine be able to maintain a steady RPM with the accelerator held in a steady position? I can't seem to maintain a steady speed when I want to. It seems like I have to constantly work the accelerator. I took a board and propped it between the seat and accelerator and set the Tach at 2000. The engine speed climbs to 2500 and then drops to 1750 repeatedly. Air and fuel filters were changed recently so I don't think that's what it is. The truck has had several major breakdowns so it has had it's high pressure oil pump replaced and has a new IPR (I don't even know what an IPR is).
Am I gun shy or is this a new problem in the making?
Am I gun shy or is this a new problem in the making?
Last edited by eshoaff; Apr 27, 2006 at 10:19 PM.
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Mine has done this also since new.
In park, bring the idle up to about 1500 rpm and hold steady. It will then drop to about 1000 rpm.
I think the throttle is drive by wire (computer controled) and the computer must be dropping rpm's if no needed load is detected.
Anyone else check this?
In park, bring the idle up to about 1500 rpm and hold steady. It will then drop to about 1000 rpm.
I think the throttle is drive by wire (computer controled) and the computer must be dropping rpm's if no needed load is detected.
Anyone else check this?
Cargo Master
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From: Too close to Houston
I don't know how drive-by-wire works but I've never driven a vehicle (gas or diesel) that delivered constant rpm for a fixed throttle position. The pedal position is more or less a "fixed power" position. It takes more power to maintain the same rpm as you increase load such as climbing an incline. Less pedal is required to maintain the same rpm going down an incline. If fixed position equalled fixed speed cruise controls would be very simple.
In a gas engine the pedal controls the throttle plate or airflow. Fuel control follows the air via injectors or carburator venturies and jets. The pedal in a diesel controls the fuel delivery into an air-rich system. I'm not sure how the diesel fly-by-wire system works but I suspect it is a fuel control since diesels don't have throttle plates.
Since constant rpm is not equal to constant power you could never maintain a set speed without moving the pedal.
In a gas engine the pedal controls the throttle plate or airflow. Fuel control follows the air via injectors or carburator venturies and jets. The pedal in a diesel controls the fuel delivery into an air-rich system. I'm not sure how the diesel fly-by-wire system works but I suspect it is a fuel control since diesels don't have throttle plates.
Since constant rpm is not equal to constant power you could never maintain a set speed without moving the pedal.
Last edited by Sport45; Apr 28, 2006 at 12:06 PM.
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From: Albuquerque
Do you have the most up-to-date PCM flash? Sounds like a problem I heard before...and there was a TBS from FORD.
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2003 F250 SD SC 142" XLT FX4 V10 Auto 4x4 3.73s
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2003 F250 SD SC 142" XLT FX4 V10 Auto 4x4 3.73s
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I should have have all updates, the truck likes to visit the Ford garage a lot. As for Sport45; I didn't have the engine under a load when I did my test. I just used a prop between the accelerator and seat frame to set the rpms at a constant speed. Rpms vary 7-8 hundred. It seems to me that they couldn't use this engine in an industrial application like powering a generator. Lights would brighten and then dim continuously.
I'm told that the accelerator is controlled electronically, so if the software is working properly then I'm wondering if the work done on the HPOP was faulty. All the warranty work orders end in: Retest, OK. I wonder how they test them. What do they use to bring the idle up if there isn't any throttle cable under the hood?
I'm told that the accelerator is controlled electronically, so if the software is working properly then I'm wondering if the work done on the HPOP was faulty. All the warranty work orders end in: Retest, OK. I wonder how they test them. What do they use to bring the idle up if there isn't any throttle cable under the hood?
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If you could divise a way to hold the pedal perfectly still, the RPMs should hold pretty much constant. I wouldn't expect to see the tach jumping all over the place, anyway. 700 to 800 RPMs is way too much.
As to the drive by wire system, that has been around since the beginning of the PSD. The 7.3s had it too.
Basically, when you step on the gas pedal, you are stepping on a resistor. (If you take a look at your gas pedal linkage under the dash, you'll find that the pedal sensor at the end looks a lot like a Throttle Position Sensor (TPS) on a gasser. The computer sends 12 volts into there, and based on what it gets back out the other side of the resistor if sets up how much fuel to dump into the engine.
I imagine that the RPM can be set using the service tool that plugs into the programming connector under the dash. The PCM has a provision to govern the engine speed to 1200 RPMs if you have a PTO engage circuit. I know that because I've done that.
IPR = Injection Pump Regulator. That sets the pressure in the high-pressure oil rail. That rail provides the hydraulic pressure to make the inkectors work.
As to the drive by wire system, that has been around since the beginning of the PSD. The 7.3s had it too.
Basically, when you step on the gas pedal, you are stepping on a resistor. (If you take a look at your gas pedal linkage under the dash, you'll find that the pedal sensor at the end looks a lot like a Throttle Position Sensor (TPS) on a gasser. The computer sends 12 volts into there, and based on what it gets back out the other side of the resistor if sets up how much fuel to dump into the engine.
I imagine that the RPM can be set using the service tool that plugs into the programming connector under the dash. The PCM has a provision to govern the engine speed to 1200 RPMs if you have a PTO engage circuit. I know that because I've done that.
IPR = Injection Pump Regulator. That sets the pressure in the high-pressure oil rail. That rail provides the hydraulic pressure to make the inkectors work.
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I guess I need to confess. Although I had changed my fuel filters a month before the problem started I couldn't help wondering if it was the filters so I spent another $60. and changed them again. There wasn't a bit of water in them but they sure looked dirty. After the change the RPMs evened out and I even got a bit more power. I guess I got some bad fuel somewhere.
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Originally Posted by eshoaff
I guess I need to confess. Although I had changed my fuel filters a month before the problem started I couldn't help wondering if it was the filters so I spent another $60. and changed them again. There wasn't a bit of water in them but they sure looked dirty. After the change the RPMs evened out and I even got a bit more power. I guess I got some bad fuel somewhere.
biz
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2003 F250 SD SC 142" XLT FX4 V10 Auto 4x4 3.73s
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I should have posted back sooner, I felt foolish since filters were the first thing to go through my mind but I've had trouble with this truck and these engines seem a lot more complex than the John Deeres I have in my forklifts. When I open that hood and see everything packed into that space; I just close it up. I'm just glad that I didn't take it back to Ford garage.