Hi all,

Wednesday evening on the way home, my truck suddenly starting misfiring and running rough. It's happened before, twice, and both times before it ended up being a spark plug or a wire. Two years ago had all the wires and plugs replaced (~50k miles on the truck since then) and about a year ago had misfire on cylinder two. I can't find the receipt at this time, but I'm certain the coil pack was replaced at that time along with that plug and wire. Now I'm getting misfires on both three and four.

It idles rough when in drive (not in park or neutral), but smooths out when given some gas and I can run it at about 45 MPH without it missing. Haven't run it any faster than that, since the SES was flashing, so I was just hoping to nurse it until I got home.

I don't have much money to replace a bunch of parts, so I was hoping I could come here and get some advice on how to narrow down the problem without shot gunning parts to it.

2002 Ford F-150 4.2L V6 2WD
~140,000 miles.

Thanks from the

 

Hi and welcome to FTE!
Hope you find some help.

My first suggestion: use the "search" button in the task bar across the top and serach for "P0303".
There are a number of threads here with lots of good info.
I think you might find some good stuff to help you.

Best of luck, and again, welcome to FTE!

 

Thanks, Brian.

I've been reading every thing that I can about the error codes I'm getting. Some of it is down right scary. Removing manifolds and such. I hope I don't have anything like that going on.

Anyway, since some people in past years had mentioned fuel injectors, I ran some cleaner in it today, hoping it would clean something up, if that was the problem. No such luck of getting away with a $5 fix.

So I read up on ignition problems and found that I could pull the wires off while the engine was running and if it changed the way the engine ran, that meant the plug was good, but if there was no change, that meant that plug was bad. So I pulled the cylinder #4 wire off the plug and no noticeable change. Also, I put it next to metal and saw no spark. I pulled the cylinder #5 wire off and heard the engine stutter. Also it sparked when next to metal.

Went to the other side, pulled the cylinder #3 wire off and no difference in the way the engine ran and no spark or crackling. Pulled the cylinder #1 wire off and again heard the engine stutter and the spark from that bad boy jumped at least an inch, maybe two.

So it looks like my problem is spark on #3 and #4 cylinders. Is there any way I can determine if it's the wire or the coil pack? Can I switch the #3 wire with the #1 wire and see if the problem follows the wire?

Thanks for any help.

 

Yes, you can swap wires around, as long as they are long enough to reach, no problem.
If you have to have new wires, I suggest OEM Motorcraft. Guys have had problems with others over the years.

Keep us posted.

 

Pull the wire off at the coil and see if there is a spark. I'm pretty sure the coil is bad because 3 and 4 are on the same coil circuit. The other possibilities are a broken driver wire or a bad driver in the PCM. The small tower coils fail quite often so that is your best bet.

 

It sure was. I swapped the #2 cylinder wire with the #3 cylinder wire and the misfires stayed on cylinder #3 and #4. Changed out the ignition coil pack and she's running smooth now.

Thanks Brian and 70f100 for the advice and input.

 

Ok, I replaced the plugs(8) and ignition coil # 4 for Error codes P0304/P0316.
Now getting a rough idle at start up and SES light is back on after 3 weeks driving. Seems same problem is back. Same error codes again.
Wires/plugs ignition coil #4 checks out as OK?

Looking for suggestions as to what to try next?

Mine is 2003 Super Crew cab F150 2WD 149K miles.

 

I also have the same error codes, P0316, P0301, P0304, AND P0174, too lean in cylinder 2. I changed the plugs recently. not sure where to go from there..

 

ok first time here! 98 f150 155.900 miles and along with some evap codes P0303 is the one im puzzled on....i kno to check plugs n wires n stuff like that but what and how do i check voltage and components to know for sure if its a coil or some kinda resistor???