01 expy 5.4 p0171 p0301 runs rough

Jeremy Slay
435

Asked by Jeremy Jul 31, 2012 at 06:31 PM about the 2001 Ford Expedition XLT 4WD

Question type: Maintenance & Repair

Last week our 2001 expedition started running rough during a rain storm.  We took it home and parked it for a couple days to let
it dry out.  Still ran rough after drying but now had a check engine light.  Got codes p0301 & p0171.  Resistance tested the coil,
checked the boot for visible defects, tested injector harness and coil harness.  All passed the spark plug was white and ash
covered so I replaced the injector and the plug.  Ran decent for a few minutes and all our problems returned.  Rescaned the
engine and got only the p0171 (system lean bank 1).  Changed 7 spark plugs (all but #4 the hard to reach one) and again the
problem is still here.  At idle I pulled all the coil wires 1 at a time (except #4) each time the miss got worse so i assume all cylinders
are now firing.  Im stuck and almost out of ideas.  Can't afford to just blindly throw parts at it.  

6 Answers

Michael Mierzejewski
2,170

Well what controls fuel on only one bank of the engine? Oxygen sensor!

6 out of 6 people think this is helpful.
Jeremy Slay
435

The day after I posted this the cylinder #1 misfire returned. Only acting up when hot or under a load. Not acting up when idling. I just switched the coil an plug boot to other cylinders to see if the misfire moves to the new cylinder. Still running rough but no new codes.

2 out of 2 people think this is helpful.
Jeremy Slay
435

For anyone following along, the misfire code followed the coil. I replaced the coil this morning and the truck runs great. Hope this helps someone.

4 out of 4 people think this is helpful.
KW93551
180

Change the coil pack intermittent spark or damaged boot

4 out of 4 people think this is helpful.
KW93551
180

P0171/P0174 Diagnostic Theory for Shops and Technicians When a vehicle has the fault code P0171 and or P0174, it means that computer can no longer automatically adjust the mixture between air and fuel. Code P0171 applies to Bank 1 and P0174 applies to Bank 2. Code P0174 mainly applies to V6 or V8 engines because 4-cylinder engines generally have only one bank, though there are a few exceptions. Some of the high performance 4-cylinder and straight 6-cylinder engines (such as those in BMW and Lexus) split the cylinders into groups of two or three and call them separate banks. When the code says that the Fuel System is "too lean," it means that the computer has been adding more and more fuel, which is called Long Term Fuel Trim. Ideally, the Long Term Fuel Trim should be close to 1 to 2 percent. When a code P0171 is set, it means that the Fuel Trim is anywhere from 15 percent to as high as 35 percent compensated. When this happens, the computer knows that there is an improper condition in the control of the Fuel System. The first step in the diagnosis of a code P0171 and/or P0174 is to look at a minimum of three ranges of the Long Term Fuel Trim numbers on a scanner. Check the idle reading—3000 RPM unloaded and 3000 RPM with at least 50 percent load. Then check the freeze frame information for the code to see which range(s) failed and what the operating conditions were.

8 out of 8 people think this is helpful.
KW93551
180

OBD II P0301 Fault Code Definition Misfire Detected in #1 Cylinder Symptoms Check Engine Light flashing Rough running, hesitation, and/or jerking when accelerating In most cases, there are no adverse conditions noticed by the driver In some cases, there may be performance problems, such as dying at stop signs or rough idling, hesitation, misfires or lack of power (especially during acceleration), and a decrease in fuel economy Common Problems That Trigger the P0301 Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable) Incorrect ignition timing Vacuum leak(s) Low or weak fuel pressure Improperly functioning EGR system Defective Mass Air Flow Sensor Defective Crankshaft and/or Camshaft Sensor Defective Throttle Position Sensor Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems

6 out of 6 people think this is helpful.

Your Answer

Add photo

Related Questions

Expedition
Looking for a Used Expedition in your area?
CarGurus has 18,397 nationwide Expedition listings starting at $2,250.
ZIP:

Search Ford Expedition Questions

Ford Expedition Experts

#1 lightGear
lightGear
Reputation 750
#2 kbro
kbro
Reputation 480
#3 oldtimer37
oldtimer37
Reputation 370
View All

Related Models For Sale

Used Ford Explorer"
1,013 Great Deals out of 52,843 listings starting at $990
Used Chevrolet Tahoe"
965 Great Deals out of 28,481 listings starting at $2,700
Used Lincoln Navigator"
151 Great Deals out of 4,771 listings starting at $3,288
Used Chevrolet Suburban"
681 Great Deals out of 19,327 listings starting at $2,200
Used Ford F-150"
2,994 Great Deals out of 151,632 listings starting at $1,000
Used GMC Yukon"
341 Great Deals out of 9,378 listings starting at $2,295
Used GMC Yukon XL"
369 Great Deals out of 10,367 listings starting at $2,995
Used Ford Excursion"
43 Great Deals out of 940 listings starting at $3,390
Used Cadillac Escalade"
279 Great Deals out of 6,640 listings starting at $2,995
Used GMC Yukon Denali"
202 Great Deals out of 6,118 listings starting at $2,995
Used Toyota Sequoia"
144 Great Deals out of 4,181 listings starting at $3,000
Used Dodge Durango"
444 Great Deals out of 21,280 listings starting at $1,000
Used Ford F-250 Super Duty"
700 Great Deals out of 36,172 listings starting at $1,995
Used Jeep Grand Cherokee"
1,210 Great Deals out of 56,701 listings starting at $795

Used Cars For Sale

2014 Ford Expedition XLT 4WD For Sale
14 Great Deals out of 255 listings starting at $27,573
2013 Ford Expedition XLT 4WD For Sale
9 Great Deals out of 90 listings starting at $25,992
2012 Ford Expedition XLT 4WD For Sale
4 Great Deals out of 78 listings starting at $19,900
2011 Ford Expedition XLT 4WD For Sale
4 Great Deals out of 135 listings starting at $17,650