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"resident smarty pants"
5,360 Posts
Discussion Starter · #1 · (Edited)
Lots of things can cause a lack of power.

The best thing to do first is to get the codes read. Be aware that the cheap code readers only read the generic codes (not Ford specific codes). If you do not have access to a good code reader, the cheap ones are worth checking, but be aware that seeing no codes may not mean there isn't an issue. You must use an OBDII / CAN compliant code reader. Autoenginuity makes a decent code reader (and there are others). The auto parts stores can scan for codes, but they will probably not have the equipment to see all the codes. Also, it is common to have issues that will not through ANY codes (unfortunately). IMO downloading ForScan Lite to a smartphone is the best thing to do ($5). You will also need an OBDII adapter (ELM327), but BAFX makes one that works well for around $25. ForScan is a GREAT code reader and a good scan tool for engine parameters. The Scangauge II is a good scan tool for engine parameters, but is a poor code reader. All tuners are poor scan tools.

With low power, I like to start with the EBP, Baro, and MAP readings. They should all be within .5 psi of each other at KOEO.

Might as well also check the temperature sensors. The following temperatures should all be very close on a totally cold engine (at least 12 hours of sitting with the engine off):

Might be wise to remove all tunes, return it to factory stock for troubleshooting
Note ANY recent work done to the vehicle/engine..

Starting with the simple things:

1. What oil and fuel filters do you use? How often are the filters changed?
Plugged fuel filters (or bypassing fuel filters due to them blinding off) can easily cause low fuel pressure and consequently poor combustion and other performance problems.
Oil is used to actuate the injectors. Poorly filtered oil (or oil filters that do not allow the drain valve to properly close) can cause issues with injectors and can affect the high pressure oil system.
OEM filters (or OEM style such as Racor or International) are essential to ensure good operation. Aftermarket oil and fuel filters have been proven to cause problems and poor performance.
Follow the recommended fuel filter change intervals - 15,000 miles with normal service and 10,000 miles with severe service (towing, biodiesel usage, etc).

2. Could you have gotten bad fuel?
Drain your water separator into a clear container and inspect it. Do you have a lot of water or contaminants? If so, it would be a good time to change the fuel filters (remember OEM , International, or Racor).

3. Is your fuel aerated (ie air in the system)?
Sometimes when fuel filters are changed, the filter caps are cross threaded, or the o-rings are damaged. Especially on the primary fuel filter, this can allow air to be drawn into the system. If you have recently changed fuel filters, you may want to pull the filters and inspect the cap threads and the o-rings - assuming the caps were not just loose.

4. What oil do you use and when did you last change it?
Again, oil is used to actuate the injectors. If the oil is old or too thick, it will affect injector operation. ONLY diesel rated CI4 or CJ4 oil should be used. Synthetic oil is a benefit.
Follow the recommended oil change intervals - 7500 miles max with regular service and 5000 miles with severe service (towing, biodiesel usage, etc). Using the proper oil is VERY important.

5. What is your oil level?
Oil levels that are too high can cause issues (aerated oil). This can impact injector operation. Also, an oil level that is too high could indicate a serious injector issue (fuel dilution of the oil). With a high oil level, always smell it to check for excess fuel dilution. Oil testing is even better.

6. Any hoses or electrical connectors loose/unattached under the hood?
Particularly inspect the MAP sensor hose, the VGT (turbo) actuator connector, MAF/IAT1 sensor connector, IAT2 sensor connector, EBP connector.

7. Any exhaust or intake leaks (at boots or pipes)?
Look for sounds and signs of leakage. Soot and oily residue can be signs of leakage around the charge air cooler system (CAC tubes) and the exhaust pipes.
It is common to have CAC system leaks from degradation caused by oil from the ccv system that weakens the boots. Also up pipe and "y" pipes can leak .... often times at the flex tubing or leaking bolted-joints.
You can also use some strips of paper taped to a dowel as a "feeler gauge" to inspect the connections while the engine is running and held at higher rpms - say 2000.
Also helpful in the search for leaks is a flashlight and mirror (when looking for soot).
As an FYI - The dealerships use smoke to test for leaks. You can too with not too much effort. Do an internet search on the subject!

8. Check your air filter "filter minder".
The filter minder works pretty well. You do not have to change the OEM air filter until the filter minder indicates you are plugging up.
It is very common for people to get 75k (and more) miles of operation on the OEM air filter. They are VERY good. There is no REAL need to change them out early.

9. Have you pulled your EGR valve or ever changed it out?
Poor combustion caused by biased sensors, bad fuel, filter issues, weak EGR valve, injector problems, etc can produce a lot of soot and even oil residue.
This is easily checked by pulling the EGR valve and inspecting it.
There are threads in the Tech Folder on pulling the valve and cleaning it.
There were also a number of design improvements to the EGR valve itself. Only you can decide to spend the money on a new EGR valve because there is no way to test them.
However, in 2008, I bought a new valve to take advantage of the design improvements.
If you pull your EGR valve, ALSO check for coolant (liquid - different than not oily residue) under the valve. This indicates a leaking EGR cooler which MUST be fixed immediately if you have this problem. The best way to check the EGR valve is to run your engine up to operating temperature and then park on a downslope. Then pull the EGR valve.
Also advisable when you pull you EGR valve is to clean out the MAP sensor hose and EBP tubes - they can get plugged up.

10. Are you getting good fuel flow?
You could have issues with plugged lines, a weak HFCM (fuel pump), or even an injector that is leaking combustion gas into the fuel system that is "back pressuring" it and restricting flow.
Pull relay labeled the IDM relay (it is for the FICM - it is #304 for my 2006) and then pull the secondary fuel filter. Crank the engine to see if you are getting good fuel flow to the secondary filter.
If you see air bubbles in the fuel, then you have a leakage of air into the fuel system or one (or more) injector issues).
If you think you have combustion gasses leaking into the fuel from a bad injector, then there are more complicated tests you can conduct to isolate the injector that is causing your problem. That process would require a separate thread to discuss and troubleshoot.

11. Bad ICP sensors and/or harnesses can cause power issues, but they usually have other symptoms like rough running, bucking/surging, and even no-starts.
It would not be a bad idea to visually check your ICP connector to see if it is oil soaked. This would indicate the need to change the sensor and replace the connector. You can run with the ICP sensor disconnected. This might be a good test to see if it makes a difference in how it drives (ie run with the sensor disconnected).

12. Wire chaffing can be an issue with these trucks.
You can check for wire chaffing by looking over the information in the links below:
Wire Chaffing Locations:
Ford DTC codes & wire chafing locations
Electrical Problems

FICM and ICP harness recall
6.0L ICP Sensor Failures

Just recieved a recall letter. Anybody else -

SORRY - the link above may not work!

13. You could have a clogged catalytic converter - but it is fairly rare.
Drop the exhaust and run it to see if there is a difference.

14. You could have a bad FICM, usually there are quite a few codes w/ a bad Fuel Injection Control Module.
Check codes and check FICM voltage (see thread in the Tech Folder). ALWAYS make sure your batteries are fully charged and have been load tested individually. Weak voltages can permanently damage your FICM and cause low power.
FICM Guide:

15. You could have clogged fuel lines or a weak fuel pressure regulator spring.
Check system (run pressure check if you can). A fuel pressure gauge is essential IMO. You must have 45 psig minimum at the secondary fuel filter test port or you can cause injector damage.
Even if you do not have clogged fuel lines or clogged filters, you have a fuel regulator that sends fuel back to the fuel tank. This spring is FREQUENTLY found to be weak.
It is very common to need to change out the spring in the fuel pressure regulator.

16. Injector stiction.
There is a small spool valve in the top of the injector that controls the flow of high oil pressure fed to the intensifier piston in the fuel injector. That spool valve only moves .017", back and forth, on and off every time the injector fires. Many factors play in to how well that valve works such as, oil temp, oil quality, normal wear, ambient temp, and many others. As this valve ages it polishes itself inside the bore of the spool valve and as the spool valve slams back and forth it can set up the condition like a suction cup, hanging the valve to one side or the other. This uncommanded uncontrollable condition is called stiction. Mostly it's a rough run cold condition but in severe cases it can be a no start or pretty harsh misfire condition. Oil that stays inside the valve on a hot engine shutdown and is allowed to cool slowly in the injector can aggravate the condition on restart, so the newest reflash uses inductive heat after shutdown to keep the oil warm, keep its viscosity low, and maximize the oil flowability to purge the oil from them. It has worked fantastic. It is an excellent preventative measure. Synthetic oil also helps IMO.

17. The turbo could be sticking:
The stock turbo is a VGT (variable geometry) turbo. IT has VANES that can be varied to control the performance of the turbo. These vanes and the parts that move the vanes can get stuck with carbon or corrosion byproducts. Many times these can be corrected by pulling the turbo and cleaning it. There is a good procedure to do this in the TECH FOLDER, but it is a fair amount of work and you should use some very specific cleaning materials.

18. Could have a bad EGR valve:
If you have a lot of black smoke and you still have your EGR system, then pull your EGR valve, inspect and clean it. If it is real dirty with sticky, black, gooey solids - then you have a combustion or fuel issue. Just cleaning the EGR valve may not be enough. You may need a new valve. No way to really test the EGR valve to see if it is good, but if it is older than a 2007 valve (maybe even a 2008 valve), I would suggest buying a new one - they have upgraded the valve with some good improvements. The EGR cleaning thread is in the Tech Folder:
6.0L Diesel: ..................Tech Folder.............. - Ford Truck Enthusiasts Forums
Scary pics of my 11,000 mile-old EGR valve - Ford Truck Enthusiasts Forums
Also, the newest flash update of your engine processors is a good idea if it hasn't been done since late 2009. If you see or smell coolant in the intake manifold after you pull the valve, you most likely have a failed EGR cooler and it needs to be corrected ASAP!

19. You could have an issue with the high pressure oil system.
You can determine this with a scan tool and watching ICP pressure, ICP volts, and IPR % duty cycle. Ultimately you may have to do a leak test with air. If so, buying the adapter for introducing the air into the IPR port is highly advised. It is possible to also have a weak HPOP. That is a little harder to determine, but it can be identified through the process of elimination.

20. Other things that are more complicated to troubleshoot and more expensive to fix (those not already discussed):
i. Sensors - Bad EBP, MAP, Baro, MAF
ii. Actuators - Turbo VGT
iii. Other instrumentation issues - IPR valve
iv. Mechanical - Bad fuel pump (HFCM), bad injectors, or a bad HPOP (high pressure oil pump). Usually a "no-start" condition will be experienced with a bad HPOP. It is a fairly big/expensive job to replace this pump.
v. Sometimes the most recent flash applied by the dealership can improve performance. They usually contain some desirable upgrades.
vi. Sometimes you can have a dragging component (ie brakes, A/C compressor, etc).
vii. Make sure you don't have a lot of white smoke. An injector could be dumping raw fuel which can cause poor engine performance.

Even a bad GPCM can cause low power and lack of acceleration. Usually you will have a code for the GPCM or individual codes for one or more glow plugs themselves. GPCM part # is YC3Z-12B533-AA.

An illuminated wrench lamp indicates the PCM is limiting power - ie in a "limp" mode.

  • Oil cooler efficiency monitor - DTC P012F stored and wrench warning lamp illuminated when the oil coolers efficiency drops below a specified threshold for a given speed and vehicle load condition.
  • FICM low voltage detection monitor - DTC P0560 stored and wrench warning lamp illuminated when PCM vehicle power (VPWR) parameter identifier (PIDS) is below 10.25V for 60 seconds or below 9V for 4 seconds.
  • Turbocharger over boost detection - DTC P0234 stored and wrench warning lamp illuminated when a turbocharger over boost condition occurs.

Hot engine tests (engine oil temp over 177 *F):
EBP should be less than 35 psi at 3800 rpm - no load
IPR should be less than 30% duty cycle at idle.

NOTE - the engine will defuel at any of the conditions below:
Defuel at 221 *F ECT (coolant temperature)
Defuel at 253 *F EOT (oil temperature)
Defuel at 4000 rpm's
Defuel at 95 mph
Defuel at 28.6 psig boost for 2005-2007 engines (and 2008 - 2010 E series) TSB 09-24-3

Turbo Guide:

"resident smarty pants"
5,360 Posts
Discussion Starter · #2 ·

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