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Ignition Coil Wire Colors. My XJS 4.0 I6 had very brittle and bad ignition coil wires. I got new pigtail connectors and rewired. I'm now getting the following fault codes: P0300 Random Misfire, P0303 Cylinder 3 Misfire, P1313 Catalyst Damage Misfire Bank 1, and P1314 Catalyst Damage Misfire Bank 2. I have switched ignition coils around reset the faults and still get the same faults showing up when I start the engine. I have all new spark plugs. Although I thought I was very careful, one thought is that I got wires mixed up when rewiring the pigtails. Below are the wire colors as I currently have them. Can someone confirm this? Any thoughts on what I should check next?
Vee, I got a set of 6 new ignition coil pigtails, then starting with cylinder 1 would clip off the old connector and splice in the new connector with crip on and heat shrink connectors. Worked front to back so I pretty sure I didn't cross the wires up. These are the pigtails and end result.
Connections are crimped, which I don't have a problem with, if done correctly, however, you're assuming the problem with the wire was at the pigtail, which I can't be sure is true. Maybe you'll want to reconsider your splice? Sitting on top of the engine like that, it will vibrate for the rest of its life. Not a great condition for a crimp. Maybe use a solder seal wire connector?
Personally, I would have run a new wire all the way back to the ECU, using GXL wire. You can get new terminal ends and extract the terminals without replacing the plastic plug itself!
Anyways, at this point, I would inspect those crimps, then inspect the rest of the wires all the way back to the ECU. THEN, I'd inspect all of the White wires, because all six come together at one point, then they again come together picking up five more wires (all four oxygen sensors and the air injection pump). All of that then goes back to the Multi-Function Relay. Of course, it could be a problem with that relay, not particularly common, but it's known to be the point of failure on a couple of posts in the past.
THEN I'd check the other wire that comes off of each coil. Those go directly back to the ECU.
When I say check, I mean look for brittleness, melty insulation, etc. Check the ECU contacts for corrosion, very common problem.
I assume you made sure to maintain the right wire at the right terminal when you replaced the pigtails?
I'm also assuming you had previously inspected the coils? Oil in the wells? These coils do not last forever.
I replace all the wire that is on top of the valve cover back to behind the valve cover where I felt the wire was no longer brittle and cracking. I used 18 AWG Stranded Wire with Silicone sheathing to take the heat. (photo below) There was oil in the injector coil wells. That has all been cleaned up and I've replace all the valve cover seals. No more oil problems. The coil maybe original. Hard to tell. However, when I switched coils around to different cylinders, I still get the fault code on cylinder #3. So, as you suggested in your post above, maybe I need to replace all the wire back to the ECU. Was originally trying to keep the rewiring project contained to just the wire under the injector coil cover.
Solder the connection for cylinder 3 and test then, I suggest. I am nearly ready to update my thread on building an injector loom and refurbing the injectors. My first effort used crimped connections and the loom performed erratically. I suspected the crimps and have rebuilt the loom using soldered connections and am about to test it. If, big if, the new loom works, then I suspect that soldered connections are not quite goood enough for short-duration pulses to things like coils and injectors.
Last edited by Greg in France; May 21, 2025 at 03:33 AM.
Vee, Greg, Thanks for your comments and suggestions. I'll go back and redo connections starting with Cylinder 3. Won't be able to get to it until the weekend. Will let you know how it goes. Cheers.
The pins have a barb in the flat side. You have to push a thin flat screwdriver down the pin from the connecting (open) end of the connector; this fallens the barb and with the scewdriver still in place, the pin can then be easily withdrawn.
1996 XJS 4.0 I6 - Ignition Coil Wire Colors
