P303 is driving me nuts

GMAN

GMAN

Dedicated LVC Member
Joined
Jan 26, 2005
Messages
4,743
Reaction score
31
Location
Spring, Texas, United States
I can't seem to shake this P303 cylinder 3 misfire code. I pulled out the coil out and replaced it with a new one I got from Max. I replaced all the other coils with new boots. I erased the code, but it comes back. What else do I need to be looking at. I have new spark plugs installed as well. I don't know what else to think of. Ideas please.
 
GMAN said:
I can't seem to shake this P303 cylinder 3 misfire code. I pulled out the coil out and replaced it with a new one I got from Max. I replaced all the other coils with new boots. I erased the code, but it comes back. What else do I need to be looking at. I have new spark plugs installed as well. I don't know what else to think of. Ideas please.
Click to expand...

G, it's possible that the one plug on #3 could still be fowled or have some other sort of problem. Swap the plugs around and put #1 in #3 and #3 in #1 and see if it still throws that code at you. If so, you may be looking at a coil for sure then. Did you use 764's?
 
also, make SURE you're repair/working on the actual #3 cylinder?..lol

just a tip/thought, you might have a miss on #3 and you've been messing with #6 hole?
 
XLRVIII said:
also, make SURE you're repair/working on the actual #3 cylinder?..lol

just a tip/thought, you might have a miss on #3 and you've been messing with #6 hole?
Click to expand...

i hate it when that happens, epically when the guy at auto zone gives you the wrong firing order
 
GMAN said:
Yea, I have the autolites. I am going to try that switching the plugs thing tomorrow.
Click to expand...

Hey GMAN long time. I had a problem like this with new plugs & wires in my 94 Sub. I finally gave up and took it to a mechanic, he couldn't find it either so I went back to the old spark plug wires and when I was changing the drivers side next to the firewall I found the plug broken. Can you imagine new plugs and one broken. I even had gapped them all, so maybe I moved the plug wrench in such a fashion it broke it. That solved my problem, so check that one that is misfiring for a hairline crack or just buy one new plug. Just my take on it. Oh swap the coils around too, can't hurt and make sure it is plugged in to the wire tight.
 
I think the problem could be the connector into the coil. Cylinder 3 connector, the tab is broken and will not snap into the coil. I didn't notice that before. That has to be the source of my problem.
 
GMAN said:
I think the problem could be the connector into the coil. Cylinder 3 connector, the tab is broken and will not snap into the coil. I didn't notice that before. That has to be the source of my problem.
Click to expand...

GMAN go to a electrical supply or a Home Depot maybe an auto suppy or Radio Shack will have this. It is called shrink tube. You get a large enough diameter to fit over one end of the plug in parts and then plug it together. Then slide the shrink tube over the two pieces that are plugged together and warm it with a match, small torch by waving it under neath, being careful not to get too close to catch the tubing on fire. It will shrink down to a custom fit and all the way down around the small wires at the end, like insulation. This will shrink tight enough to hold it together where the voltage going thru will not blow it apart. If later you need to replace the coil again, then just carefully cut off the shrink tube and redo it with new coil.
http://cableorganizer.com/heat-shrink/6-1-heat-shrink-tube.html,,
 
I took another look at cylinder 3, and there is FOD down at the bottom that is stuck under and probably around the spark plug. I can't get the spark plug sock around the spark plug to get it out. Probably the plug isn't seated properly. I'm going to try to blast it with some air.
 
oh, i found the rubber insert from a spark plug socket jammed down on top of of one of tiffany's spark plugs...what a pita that was to get out
 
GMAN said:
I took another look at cylinder 3, and there is FOD down at the bottom that is stuck under and probably around the spark plug. I can't get the spark plug sock around the spark plug to get it out. Probably the plug isn't seated properly. I'm going to try to blast it with some air.
Click to expand...

I have dental tools with hooks on the end to get out the O rings and plastic washers in the suspension solenoids. These would work for this also. There is also a tool that is skinney and when you push the top of the tool it opens little wire fingers that could grab something like this to pull it out. Just some thoughts. I do not think you will be able to air blast it out.
 
Well, I swapped spark plugs and I swapped coils. The misfire stayed right there at cylinder three. What else can it be?
 
Last edited:
ive seen bad wires for the injector, unplug it and look on the connector one side says b+ check for b+ with key on the other side is ground and is switched by the pcm
 
noid light not necessary, get a stethoscope w/probe and listen to injector, see if #3 injector sounds like other injectors, If all go click click and #3 goes thud thud, it is a dad injector. if there is no noise just use a 12 test light check to see if red wire has voltage, then use test light across both wires and see if it flashes, if no light suspect wiring or computer. oh yeah run a compression check. what does it sound like when you crank the engine over, does it goe ruhhh, ruhhh, ruhhh, or ruhhh, ruhhh raaaaah. you could have a broken valve spring with low compression on that cylinder.
 
GMAN said:
Well, I swapped spark plugs and I swapped coils. The misfire stayed right there at cylinder three. What else can it be?
Click to expand...

Gman I had a '94 SHO and the engine blew in it so I ended up getting a used one from a junk yard. I had mech. go thru it and replace timing belts etc. Once installed the no. 1 cylinder had a miss. After I got rid of it, I remembered there was a known problem with some kind of brass or bronze oil busings on the valves or lifters that could leak oil around it and this would cause a miss. I have no idea if this could be your problem, but it might be.
 
That's it, I'm taking it to my mechanic. Get this done once and for all. I need to go to my junk yard stash tomorrow and grab some injectors. Are the injectors the same across all years of Marks? There are two Gen 1's I can pick from, and a 97 Continental. Are all they all the same?
 
So did you get it fixed yet? You shouldn't be driving it with a miss for too long.
 
Well, I think I've figured out the problem. I took it to my buddies shop for him to look at it. All the coils have spark, new 764 plugs are in. Compression test done, and cylinder 3 has 120lbs of pressure. Everything is leaning towards a fowled up fuel injector. So I am going to replace that injector with a new Motorcraft one.
 
You must log in or register to reply here.

Members online

No members online now.
Total: 1,712 (members: 0, guests: 1,712)
Back
Top