#3 cylinder misfire. Fuel injector wiring? - F150online Forums

Go Back  F150online Forums > Powertrain & Mechanical > V8 Engines
#3 cylinder misfire. Fuel injector wiring? > #3 cylinder misfire. Fuel injector wiring?

#3 cylinder misfire. Fuel injector wiring?


Old 08-03-2005, 06:08 PM
Thread Starter
Join Date: Oct 2001
Location: Tucson, AZ
Posts: 65
#3 cylinder misfire. Fuel injector wiring?

A couple weeks ago I started getting a P0403 code. I replaced the EDIS coil packs, plug wires, and plugs. Still misfiring. I replaced the #3 fuel injector. Same problem. Checked for vacuum leaks and any physical damage on or around the cylinder. Everything else is fine. Since the misfire is not consistent (the engine will run smooth for about 10 seconds and start misfiring and off and on), could it be the fuel injector harness or wiring on that injector? If so, how could I check that? What else should I look for?
Reply With Quote
Old 08-03-2005, 09:32 PM
Senior Member
Join Date: Jul 2004
Location: Easton, Pa.
Posts: 5,635
Hold on here.
A #3 cylinder miss is not a code P0403.
What am I missing?
You better look for an EGR fault!
Ignition work is not going to fix an EGR fault.
Reply With Quote
Old 08-05-2005, 04:17 PM
Thread Starter
Join Date: Oct 2001
Location: Tucson, AZ
Posts: 65
My bad. I must've wrote the code down wrong. The code reader clearly said #3 cylinder misfire. I had an EGR valve problem, but I already replaced that. That's probably where I got the code from.
Reply With Quote
Old 08-07-2005, 02:53 PM
Junior Member
Join Date: Aug 2005
Location: California
Posts: 1
Same year, same great history, same miss. Same code (0303) same steps so far (plug, wires, coil, and cleaned injectors). Talked to a Ford dealer but that was hopless. When I was done I was sure I knew more than he did and I don't know jack! I have seen multiple threads here on the #3 going bad and no real solution. Why aren't the other 7 cylinders doing this? Computer?
Reply With Quote
Old 08-07-2005, 03:30 PM
Senior Member
Join Date: Jul 2004
Location: Easton, Pa.
Posts: 5,635
Some cases can be quite involved. If your sure the work done has no flaws then it's time to get deeper in to the troubleshooting.
This begins to get out of the relm of the owner ability.
Compression check, vacuum gauge look to see what the vacuum is doing.
An ignition scope check etc.
The way the computer detects a cylinder that has a problem is quite involved.
The cam sensor is used as a basis to time the rotation of the crank indicating the power the cylinder adds to rotation. It must be within a time frame plus a little tolerence, that is matched against a table that is built in the computer's memory. This table is even modified over time to fit the average for the engine.
I'm just alerting you to how deep this all gets. Anything that causes detection outside the limits will trigger the code and if bad enough you will feel a miss.
Plugs, gas additive deposits, coil, wire, injector, water in the fuel, outside moisture, marginal detection, air leak at the peticular cylinder intake port etc.
You have about the whole picture here and some of it you can't deal with yourself. The dealers even have a hard time with the whole thing when they don't know enough about it and won't get deep enough into solving the faults.
One thing's for sure; if a dealer does take the time, you have to pay for that time even though it gets excessive for what the problem turns out to be.
Good luck.
Reply With Quote
Old 08-15-2005, 10:57 PM
Junior Member
Join Date: Jul 2005
Location: Timmins, Ont, Canada
Posts: 28
Have a P0302 code come up on Saturday, misfired for about 20 minutes, then ok; SES light stayed on all weekend, without a miss. Started it today at noon, misfire all the way home & back, intermittent, worse under heavier throttle. Friend mechanic with scanner read code, #2 misfire. Changed plugs 2000 miles ago. Put dielectric compound on all plug terminals. I think maybe not enough dielectric lube. Pulled off that plug cap, quick visual inspection, frigged with it when putting it back on, to clean terminal. Also pulled #2 injector plug off of injector, check for corrosion, etc, ok. Put back on, cleared code, no miss. No code. Just before doing this, we could make it miss on demand with park brake on and a bit of throttle, was even misfiring when giving a good poke of fuel in Park.
My advice, clean (or replace) wires and terminals, put LOTS of dielectric lube in terminals and put some in every connection you can get it into. Will follow my own advice very, very soon.
Reply With Quote

Related Topics
Thread Starter
Last Post
2004 - 2008 F-150
09-28-2017 09:25 AM
V8 Engines
12-30-2016 11:04 PM
V8 Engines
08-23-2015 08:01 PM
1997 - 2003 F-150
07-25-2015 10:30 AM
1997 - 2003 F-150
07-09-2015 07:30 PM

Thread Tools
Search this Thread
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


All times are GMT -4. The time now is 01:33 PM.

  • Ask a Question
    Get answers from community experts
Question Title:
Your question will be posted in: