Low power question
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Senior User
Joined: May 2004
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From: Osceola, WI
Low power question
Hi everyone!
I just bought a 1995 F250 powerstroke 4x4 with a 5-speed and have done a lot of work to it already. I replaced all of the hoses and o-rings on the fuel filter housing and the lift pump as well with great success!
Now onto my question: I have put over 300 miles on the truck and it runs great most times when warm. When it's cold, it runs rough and is low on power. Then, it will all of a sudden gain power and drive normally. One time it was low on power for over 35 miles and never did come out of the low power (really disappointing!). It has 222k on the clock and I am looking for ideas. Any suggestions?
I just bought a 1995 F250 powerstroke 4x4 with a 5-speed and have done a lot of work to it already. I replaced all of the hoses and o-rings on the fuel filter housing and the lift pump as well with great success!
Now onto my question: I have put over 300 miles on the truck and it runs great most times when warm. When it's cold, it runs rough and is low on power. Then, it will all of a sudden gain power and drive normally. One time it was low on power for over 35 miles and never did come out of the low power (really disappointing!). It has 222k on the clock and I am looking for ideas. Any suggestions?
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Joined: Nov 2007
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From: West Texas
Have you had one of these trucks before? It sounds like the exhaust backpressure valve. It's doing what it is supposed to do when it's cold by gagging the exhaust to help it warmup faster. It should kick off when you get in the throttle then come back on when you steady out again.
Most people here say to unplug it but personally I think it is necessary. Diesels don't like cold and it really needs all the help it can get warming up. I even took my fan off all winter and it still doesn't like to get warm for about 25 to 30 miles of highway when it's below freezing out.
Most people here say to unplug it but personally I think it is necessary. Diesels don't like cold and it really needs all the help it can get warming up. I even took my fan off all winter and it still doesn't like to get warm for about 25 to 30 miles of highway when it's below freezing out.
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From: Osceola, WI
Hi RRanch,
I don't think that it it's the backpressure valve in this instance because all of these issues have been above 40F. I also haven't heard the normal hissing that is evident when the valve is closed, but I could be wrong.
It could be that the backpressure valve isn't operating properly though. I'll check it when it happens again and see if it's closed or open.
Any other ideas? What about the backpressure sensor?
I don't think that it it's the backpressure valve in this instance because all of these issues have been above 40F. I also haven't heard the normal hissing that is evident when the valve is closed, but I could be wrong.
It could be that the backpressure valve isn't operating properly though. I'll check it when it happens again and see if it's closed or open.
Any other ideas? What about the backpressure sensor?
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From: emporium
im assuming it happens when you first start it up for the day. it might be 40 degrees out but if the truck has been sitting all day and not in the direct sunlight then the motor is still cold when you start it up. its normal. best thing is to let it take its time and warm up. dont get all up on the throttle to take off. its just its normal way of warming up the motor
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Joined: Apr 2005
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From: Anchorage, Alaska
At 40 degrees, it should fire up and run great!
I'd check the back pressure sensor and the tube that supplies the sensor for blockage. The tube comes off the passenger side exhaust manifold and runs up the front of the engine. If you follow it up you'll find the sensor, either right above the water pump, or near the front of engine fuel filter area.
You can clean up both or either, or just replace them. If you can blow through the tube, then its not clogged. Check the fitting where it connects at the sensor and at the manifold. Drill out any carbon with a drill (usually just a bit with your fingers will do it, but not always).
Injectors can also cause this problem, but the symptom doesn't usually last 35 miles down the road. Possible sticking IPR valve as well.
FYI - this back pressure sensor is in no way connected to the warmup valve after the turbo outlet.
I'd check the back pressure sensor and the tube that supplies the sensor for blockage. The tube comes off the passenger side exhaust manifold and runs up the front of the engine. If you follow it up you'll find the sensor, either right above the water pump, or near the front of engine fuel filter area.
You can clean up both or either, or just replace them. If you can blow through the tube, then its not clogged. Check the fitting where it connects at the sensor and at the manifold. Drill out any carbon with a drill (usually just a bit with your fingers will do it, but not always).
Injectors can also cause this problem, but the symptom doesn't usually last 35 miles down the road. Possible sticking IPR valve as well.
FYI - this back pressure sensor is in no way connected to the warmup valve after the turbo outlet.
Senior User
Joined: Apr 2005
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From: Anchorage, Alaska
IPR - Injection Pressure Regulator. It is mounted in the high pressure pump just under and to the driver's side of the fuel filter housing.
You kind of have to monitor the injection control pressure (ICP) somehow while driving it with the symptom occurring. Unfortunately, they aren't cheap to throw on either.
I can't think of any other way of monitoring the ICP than with a scan tool. A gauge won't work unless you have one that goes to 4000 psi and adapts somewhere.
You kind of have to monitor the injection control pressure (ICP) somehow while driving it with the symptom occurring. Unfortunately, they aren't cheap to throw on either.
I can't think of any other way of monitoring the ICP than with a scan tool. A gauge won't work unless you have one that goes to 4000 psi and adapts somewhere.
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Joined: May 2004
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From: Osceola, WI
I checked out the backpressure sensor and it was clogged. I haven't driven it since I cleaned it, but that could be the problem I guess. I'll check to see if I can look into the injector pressure regulator as well. That would be a lot less expensive than injectors!!!
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From: West Texas
What exactly is the purpose of the backpressure sensor? I'm trying to diagnose mine for a low power black smoke problem too. THought I had it fixed when I took apart and repaired the IPR but it came back again after a couple days. My temp also climbs a bit on the gauge when the power is low.
I've also noticed the glow plugs come on for a good 30 seconds or so even when it's 80 degrees outside. Something ain't right here. It's got to be a sensor somewhere. Problem is, mine is EEC4 still. I haven't had the time to convert it to obd2 yet. These suck to diagnose when you can't see a datastream!
I've also noticed the glow plugs come on for a good 30 seconds or so even when it's 80 degrees outside. Something ain't right here. It's got to be a sensor somewhere. Problem is, mine is EEC4 still. I haven't had the time to convert it to obd2 yet. These suck to diagnose when you can't see a datastream!
Post Fiend
Joined: Dec 2009
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From: Livoina,La
I've also noticed the glow plugs come on for a good 30 seconds or so even when it's 80 degrees outside. Something ain't right here. It's got to be a sensor somewhere. Problem is, mine is EEC4 still. I haven't had the time to convert it to obd2 yet. These suck to diagnose when you can't see a datastream![/quote]
My GP would stay on for 2 min no matter what the outside temps was and i had a bad EOT sensor might want to check to see if it's reading the correct temps should be close to outside temps.
My GP would stay on for 2 min no matter what the outside temps was and i had a bad EOT sensor might want to check to see if it's reading the correct temps should be close to outside temps.
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