When does the limp mode kick in and what does it do to the truck

satcom40 said:

When does the limp mode kick in and what does it do to the truck

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Limp mode? Could be anything. Mostly you can experience a "de-fueling" when you run very low on fuel.

Not sure what you're speaking of with "de-fueling" Vince but on my truck limp has to do with the transmission only shifting as far as 2nd gear and increasing the line pressure in the transmission to firm up the shifts and prevent breakage. Not saying these trucks are all the same, but thats what mine does, it happened to me one time when I forgot to put the dome light fuse back in after working on my truck

Depends on if you're talking about tranny limp mode or engine limp mode. I've had tranny limp mode happen when I uped the power too much without helping out the tranny. The tow-haul light flashes and it shifts like crap. I've never had limp mode on the engine, just total failure.

Theres a limp mode in the trans, where you only have 2nd gear, theres a limp mode at low fuel pressure that affects the injectors, so they dont damage, you have "de-fueling" in high temperature situations, you might even include the hvac when you lose vacuum, it Defaults to defrost only.

I was thinking low fuel when my low fuel lite come on I have about 6-8 gal left in the tank and the other day it came on and the truck acted funny.

Time for a harpoon mod....?

Got air trapped, sounds like.

satcom40 said:

I was thinking low fuel when my low fuel lite come on I have about 6-8 gal left in the tank and the other day it came on and the truck acted funny.

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Thats when the "de-fueling" starts. When the low fuel light comes on, the pcm will start to "shut off" random injectors. It will feel kind of like a misfire. This is necessary because the 6.0 injectors are very sensitive to fuel issues. Thats another reason I cringe when someone wants to use bio diesel in the 6.0.

tsb 06-13-3

TSB
06-13-3 MISFIRE, LACK OF POWER, BUCK / JERK, EXCESSIVE SMOKE, CRANK / NO START - 6.0L ENGINE - DIAGNOSTICS FOR FUEL SYSTEM - SERVICE TIPS

Publication Date: June 16, 2006

FORD: 2003-2005 Excursion
2003-2007 F-Super Duty
2004-2006 E-Series


This article supersedes TSB 06-9-7 to update the vehicle line coverage.

ISSUE:
Some 6.0L vehicles may exhibit a misfire, lack of power, buck / jerk, excessive smoke or crank / no start. There are several potential causes for these symptoms.

ACTION:
If normal diagnostics lead to an injector concern, use the following diagnostics to confirm the cause of injector failure and / or to rule out other conditions which may cause the same symptoms as a failed injector.

NOTE: IF DIAGNOSING A LACK OF POWER CONDITION, BE AWARE 2005 AND FORWARD MODEL YEAR VEHICLES HAVE A "FORCED LIMITED POWER" STRATEGY WHICH LIMITS INJECTION CONTROL PRESSURE (ICP) WHEN THE FUEL LEVEL IN THE TANK GETS VERY LOW (WELL AFTER THE LOW FUEL LIGHT COMES ON). WHEN THIS OCCURS, DIAGNOSTIC TROUBLE CODE (DTC) P115A WILL BE STORED IN THE POWERTRAIN CONTROL MODULE (PCM).



LOW OR NEGATIVE FUEL PRESSURE

Internal injector damage can be caused by lack of fuel system supply pressure. Restricted fuel filters and / or fuel line(s), or an inoperative fuel pump can create a low or negative fuel supply pressure. Low or negative pressures may hinder the return stroke of the injector intensifier plunger to its rest position, leading to internal injector damage. To diagnose for low or negative fuel pressure and to confirm if any injectors have been damaged:

Perform standard diagnostic procedures including verification of supply fuel pressure while the symptom is evident, or during a 0-50 MPH (0-80 Km/h) wide open throttle (WOT) acceleration (full load).
Repair causes for low pressure on the supply side of the fuel system.
Diagnose for failed injector(s) only after rectifying fuel supply pressure.
Recheck the fuel pressure after repairs by repeating the 0-50 MPH (0-80 Km/h) WOT acceleration (full load) test.
COMBUSTION GAS ENTERING THE FUEL SYSTEM

Inert combustion gas in an injector can cause a random misfire in one or many cylinders. Combustion gas may leak past the injector's needle and seat, or the copper combustion seal. Once the combustion gas enters the fuel rail in the cylinder head, it then distributes to other injectors, typically on the same bank. To diagnose for combustion gas entering the fuel system:

Remove outlet fuel lines from the fuel filter housing on top of engine.
Install a balloon over each fuel line with a zip tie.
Disable the fuel pump and fuel injection control module (FICM) relays.
Crank engine and watch for compression pulses in the balloon.
For each line where compression pulses are evident, remove all but one (1) of the glow plugs from the affected cylinder head(s).
Crank engine and watch again for compression pulses.
Remove the glow plug and transfer it to the next cylinder in the head and repeat Step 6.
For each cylinder where compression pulses are evident remove injector(s) and inspect copper gasket and lower O-ring, replace if necessary. If gasket(s) and O-ring(s) are OK replace injector(s). Retest to confirm repair.
NOTE: ANY TIME AN INJECTOR CLAMP IS LOOSENED AND / OR INJECTOR REMOVED, THE COPPER GASKET AND O-RINGS MUST BE REPLACED, THEY CAN NEVER BE REUSED.



Copper Gasket Inspection

Remove the suspect injector and inspect for a missing or damaged copper washer. Review repair history as a missing injector copper washer is most likely caused by improper injector torque at a prior repair for injector replacement.
Using an injector, that is not damaged, install a new copper washer and install the injector per Workshop Manual Procedure 303-04C and tighten to 24 lb-ft (33 N-m).
NOTE: SUPER DUTY VEHICLES BUILT 1/16/2006 AND LATER, AND ECONOLINE VEHICLES BUILT 1/23/2006 AND LATER, INJECTOR TORQUE IS 26 LB-FT (35 N-m) AND UTILIZES A T-45 TORX BIT.



Remove injector and inspect copper washer crush pattern. An even circular crush pattern should be visible on sealing surface of copper washer. If the crush pattern is not visible, or not a complete even circular pattern (c shape pattern), the copper injector washer can leak or fail prematurely.
Additional possible causes of damage to the copper washer could be:
Damaged injector hold down.
Hold down bolt stretched from improper torque.
Damaged injector.
Damaged injector cup.
NOTE: AFTER REPLACEMENT OF ANY FAULTY COMPONENTS - WITH NEW COPPER WASHER REPEAT INJECTOR COPPER WASHER CRUSH TEST TO VERIFY CORRECT CRUSH PATTERN.



NOTE: ANY TIME AN INJECTOR CLAMP IS LOOSENED AND / OR INJECTOR REMOVED, THE COPPER GASKET AND O-RINGS MUST BE REPLACED, THEY CAN NEVER BE REUSED.



ERRATIC HIGH PRESSURE OIL SUPPLY

Erratic supply of high pressure oil to injectors may cause a rough running engine. High pressure oil flow can be disrupted by faulty check valve(s) or a faulty Injection Pressure Regulator (IPR) valve.

To diagnose, first perform a slow neutral run up in park / neutral. If the engine runs rough between 1200 and 2300 RPM proceed to Check Valve Diagnosis; if the engine runs rough between 3000 and 4000 RPM, perform PC/ED pinpoint test Q, if the engine continues to run rough between 3000 and 4000 RPM after having validated the ICP sensor and connector, then replace the IPR valve.

Check Valve Diagnosis

To isolate the bank with the faulty check valve, disconnect all of the injector electrical connectors on one bank.
Perform a Power Balance test. Engine misfires should be constant on the four disconnected cylinders and the operational cylinders should be contributing evenly.
Repeat Steps 1 and 2 on the opposite bank.
If the operating contribution is erratic on one bank, replace the check valve on that bank.

PART NUMBER PART NAME
3C3Z-9E527-AE Injector 2003-2004
4C3Z-9E527-AA Injector 2004 - Current
3C3Z-9229-AA O-Ring and Gasket
3C3Z-9324-AA Check Valve 2003-2004
5C3Z-9A332-A Check Valve 2004 - Current
3C3Z-9C968-AA IPR valve

Well it's running just fine now. no codes I will hope for the best thanks for the infor

Limp mode....

Isn't that when you drink too much and your (you know what) goes limp when the time comes to use it at WOT... but instead your in limp mode!!!!

Oh.... your probably talking about the 6.0L motor aren't you... sorry!!!!

Beachbumcook said:

Oh.... your probably talking about the 6.0L motor aren't you... sorry!!!!

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Todd's six point slow liter is ALWAYS in limp mode.

Skandocious said:

Todd's six point slow liter is ALWAYS in limp mode.

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Is not hippie boy!!

Are you saying that anytime my Low Fuel light comes on my truck goes to limp? SOB.. I got the Harpoon but even when it comes on I got like 10 Gallons of fuel.. Normally I run it another 80 miles before I fill up.. That might be why my MPG is acting funny because the injectors are cutting off to save themselves even tho I have plenty of fuel..

Guess I need to fill up immediately when the Low Fuel comes on

Skandocious said:

Todd's six point slow liter is ALWAYS in limp mode.

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Notice he took the signature off I made him? Because its a tearful memory!.. I'll never FORGET the day it happened.. Here I am at a $60/plate Steak House with a hottie that I'm wanting to plant the seed in and I got Todd calling me.. It blew up.. It's dead.. I don't know what I did.. Man that date was PISSED! Told her I couldn't help it, I'm a Diesel Junkie and my boys needed me LMAO..

Lets just say the Seed DIDNT get planted that night.. But I don't hate Todd for it.. I just laugh my rear end off because it took my buddy blowing up his engine for me not to go planting.. Which was a good thing after all! I heard through the grapevine shes a biter if you know what i mean

Ah yeah, I remember it well.....Sowing those wild oats......and praying for crop failure...

Hahhahaha No kidding!

Hey Storm I didn't know you made that sig pic for Todd. Wanna make one for me?

Skandocious said:

Hey Storm I didn't know you made that sig pic for Todd. Wanna make one for me?

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Storm ROCKS with the graphics!! I used to think I was good, but not even close to good.

Storm- I didn't take it off due to painful memory, i took it off because it's not my baby anymore.

Crap.. Shoulda kept my mouth shut.. ;-) Shoot me a PM with whatcha want and I'll throw something together..