01 expy 5.4 p0171 p0301 runs rough

795

Asked by 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.  

17 Answers

3,300

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

10 out of 10 people think this is helpful.
795

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.

6 out of 6 people think this is helpful.
795

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.

8 out of 8 people think this is helpful.
340

Change the coil pack intermittent spark or damaged boot

4 out of 4 people think this is helpful.
340

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.

15 out of 15 people think this is helpful.
340

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

13 out of 13 people think this is helpful.
150

Just for anyone following... These problems are VERY common on these ford motors. Anytime you have this problem after rainy weather, save your $50+ on coil over pack and new plug, and go outside remove/disconnect the coil over pack and blow it out with a air compressor for a few minutes. The reason for it is simple. The water from the road has splashed up in the engine bay and water has splashed into where the spark plug/coil pack is located. Just water throwing the code and making it run rough. My wife has this happen about 3 Xs a year bc she likes to drive through water puddles on the road. Easy fix. My family mechanic didn't even charge me and showed me what was happening and how to fix it.

15 out of 15 people think this is helpful.
90

Hey Mark what coil did you change? I came home and was revving my truck then the check engine light came on and it cuts off, since then I have to put my foot on the gas for it to start occasionally it start sometime, then some time it just backfire and doesn't start. I chant the fuel pump and the fuel pressure module and it still not working and if it start the moment I take my foot off the gas it shuts off and it won't taking any rev. Can someone help me please. This is a 2002 expedition.

9 out of 9 people think this is helpful.
10

Took my truck in and put on stated 3 7 are missfiring did go through large puddles in order to return home does all it need to have them blown out. Should the coil and plug be changed not alot of money to spend on fix.

1 out of 1 people think this is helpful.
80

Not sure how to fix this but I'm having close to the same problem check engine light came on got the same trouble codes Bank number 8 running Too lean started running worse after month changed all 8 coil packs clean injectors and change all 8 spark plugs still running rough any advice. could this be an oxygen sensor at this point I don't detect any vacuum leaks runs more rough between 35 and 55 if I put it in overdrive runs better because rpms are higher. if anybody could tell me what the next step would be I'd appreciate it thank you.

8 out of 8 people think this is helpful.
80

I have a 2003 with 5.4 changed plugs ,coils and mass air air filter and o2 sensors and still idles fine untill gets hot then will not take the fuel amd will loose all power as if not gettin gas . Please help ps. Could the cats be clogged up has over 300k on them but only about 150/180k on this engine.

8 out of 8 people think this is helpful.
20

I just had new plugs and coils put in and also had my mass air flow sensor put in, but I'm still having problems like it still has smoke coming out my tail pipes... what else could be causing this.need help

2 out of 2 people think this is helpful.
60

Hi there, been though all this replacing stuff like all of you. All of it was done because our machanic told my husband it needed done. Would alway run fine after new spark plugs, then come back a month later. Took the wife doing some studying. If a triton motor leaks from the tapped covers, it goes into the spark plug holes and carbon marks the spark plug and cause a misfire. Our machanic was like no way, but did the gaskets replacement anyway. You know what two years later the truck is running fine, and we have some backup parts for it. This is the first thing to look for with a misfire on this motor, oil in the spark plug wells.

3 out of 3 people think this is helpful.
60

Hi there, been though all this replacing stuff like all of you. All of it was done because our machanic told my husband it needed done. Would alway run fine after new spark plugs, then come back a month later. Took the wife doing some studying. If a triton motor leaks from the tapped covers, it goes into the spark plug holes and causes carbon marks the spark plug and causes a misfire. Our machanic was like no way, but did the gaskets replacement anyway. You know what two years later the truck is running fine, and we have some backup parts for it. This is the first thing to look for with a misfire on this motor, oil in the spark plug wells.

3 out of 3 people think this is helpful.
10

Are there separate gaskets for each plug?

1 out of 1 people think this is helpful.

Check your MAF - Master air flow sensor & connector

Why is the "tapped covers" ?

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