Hello all,I come here looking for advice on my 2001 F150 5.4. The issue started about 3 days ago after a 200-mile trip to pick up an ATV down in Kentucky. The truck shut off and died on the highway after hitting a bump but immediately fired right back up! I proceeded to go and pick up the quad came back home with zero issues. The next day I drove to work yet again no issues, but upon leaving work and heading home my truck started to stumble and fall on its face. I drove home back to work and hooked up the scanner pulled a P0303 Code indicating that cylinder 3 had a misfire. I called up my local Ford dealer and ordered new plugs and one new Motorcraft coil. I replace them, cleared all my dtc's and keep alive memory, started the truck and the problem remained! I did a cylinder contribution test and all of my other cylinders are running perfectly flat at 0 besides cylinder 3, It is ranging anywhere from -10 to about -30. When I give it a little bit of throttle it bounces right back up to zero let off the throttle and it starts bouncing around again. After that I shut the truck off and started it up and cylinder 1 2 and 3 all had a quick drop but then went right back up to zero besides 3. So after that I pulled the coil and plug and went ahead and swapped it with cylinder 1 cleared all dtc's and keep alive memory started the truck and the problem remained yet again. I brought the truck home removed all the coils, all the plugs and did a compression test, everything is right around 165 to 175 ( Did the test twice ) however that is engine was cold due to the fact that I had to chase down a compression tester after I had already removed my plugs and coils. Cylinder 3 was at 175 I also change the fuel filter now the only thing left that I can think of as far as what it could be would be a fuel injector or a plugged up cat! The Baro Hz was a little on the low side for a little low for me here in Ohio at 155hz and 28.5. Also the cats have a rattle to them . So that leads me to believe I have a bad cat ! Crawled under the truck and and both of my down stream o2 sensors were very lose tightened them up and once again cleared everything and same thing cylinder 3 was showing same sympoms? Also have the p1000 code and a bank 1 lean code I am at my whitz end and not sure where to go from here. I also unplugged injector 3 and no change in engine idle, but I did the old screwdriver to injector to ear trick and could hear the injector functioning just fine! then off when I unplugged it. Any and all input would be more than helpful ! Thanks in advance

I've only had the truck for about 10,000 miles and have had absolutely zero issues with it until now.

Truck has 169,000 miles on it.

 

bad cat should effect one bank, not just one cylinder... If you changed the COP and plug and still have misfire, that leaves the electrical plug ( bad or bent pins), or the injector............ since compression is OK.

 

Steve , thanks for the reply , the plug going to COP 3 and injector 3 are the same readings as the others I checked , cylinder 1, 2 , and 4 didn't feel the need to check the others ! I was watching a video and a 2002 expedition had a similar issue on cylinder 5 only, and turned out the cat was burnt and causing the gasses from the exhaust to form a turbulence and not allow the burnt gasses to escape the cylinder correctly , causing it to trip CEL and poor performance. Also the rattling ( no heat sheilds on them ) is what led me to believe that the Cats Could Be the issue along with the both downstream o2 sensors being very loose

 

Long story.
From all of it, my suspicion is a vibration induced electrical issue.
Check the crank sensor plugup seating.
Reseat fuses and relays involved with PCM, Coil and Fuel Injector power.
Check ground straps and ground points.
PCM connector tightness.
All coil and injector plugs for seating.
Cats won't be cylinder selective for misfire.
My feeling is the cylinder misfires are a secondary result of an electrical issue.
The 30x codes are the result of the crank sensor measuring slow rotation time in the affected cylinder as compared to the normal engine running average.
The P1000 is a normal result of forced clearing of any code or removing power from the PCM.
It triggers a full system diagnostics each time you do a Clear and will remain until all 8 PIDS finish testing ok, then the code will clear by itself unless a trouble was detected..
A bank 1 lean code (171) is an air leak into the intake tract or an exhaust leak just ahead of the Ox sensor that is detecting it.
Look at bank 1 Long Term Fuel Trim table to see the shift that causes the code. Compare to bank 2.
Good luck.

 

Bluegrass , thank you for your response I've read much of your input on other members post and have been impressed . The possibility of an electrical connection is possible due to the fact that when I hit that bump on the highway in the truck stalled, I've removed and reinstalled all injector and COP plugs and have checked for loose or dirty ground wires ( Will remove and clean tommorrow morning) . Have yet to check relays and fuses but will give them a check as well . Fairly sure all vacuum lines are good, ran a propane torch or crossed all of them and didn't affect the idle at all. When driving and going to wide open throttle truck stumbles and causes transmisson to shift different than before. I also read a post that I believe was on here can't remember the OP but they were talking about a stuck intake valve however correct me if I'm wrong but if I had a stuck intake valve on cylinder 3 compression would have been different than the other cylinders?

 

Also I do have the famous 5.4 cylinder 4 exhaust manifold stud broke and leaking

 

The P0303 is on bank #1.
The P0171 is bank #1.
The misfire will pass unused oxygen to the O2B1S1.
The PCM will interpret the excess oxygen as a lean condiction.

The fact that the injector clicks doesn’t indicate if or how much fuel it flows.
I’d swap that injector with one on bank #2 and see if the issues follows.