Used my new code reader---craftsman CanOBD2 model 87702. Worked great on the Jag, Volvo, and Toyota. At 124 bucks it is one you can add it to your list of possibles. On the X300 it gave me two codes: Jag specific P1314 misfire rate catalyst damage fault bank 2 and generic P0420 catalyst system efficiency below threshold bank one.

Am I wrong in assuming that code P1314 may be a misfire at the coils? Or is it the catalytic converter?

I think P0420 is probably an o2 sensor, and hopefully not the catalytic converter.

Any insight would be great. Thanks

 

Both of your assumptions are reasonable.

 

I once had a misfire code in a previous vehicle upon scanning for codes. It ended up being a loose connection on a spark plug wire, my car felt like it was firing on 3 cylinders on hills.
If you haven't checked your plug connections already it might be worth a look before getting worried about the coils as they can be pricey but they are known to go bad on x300s from what I hear
Lets hope its just a loose connection
Aloha

 

pulled the cover and took a look at the coils and wires. On two of the plugs (wire side) some of the insulation was dry and cracked---I could see bare wires between the plug and the end of the insulation. I applied some electrical tape as a stop gap measure for now. I don't like the way all the wires feed right into the larger loom--looks like replacing the entire wire would be a pain. I was also missing the gasket off the inside of the cover---hmmm bare wires & moisture= problem. Must be away to remove the plugs, trim the wire a bit and reinstall the plug. Might as well change the spark plugs and all while I am there.

 

Scott:
that is the primary (low voltage) side of the coil - I believe you will find it is not your problem, unless the conductors are actually toughing or grounded. As you remove the coils to change the plugs, look for cracked plug boots.

Are your O2 sensor voltage readings cycling low to high on all four positions?

 

Sparkenzap, I am going to order the plug wires, coil gaskets, and plug gaskets so I can try to get at it this weekend. I am very pressed for time during the week, unfortunately. I need to look at my X300 manual for the actual location of the plug wires---I've never worked on this type of car before---different. As far as the o2 sensors are concerned I'm not sure what you mean about the four positions. Forgive me, but in the army I worked in the motorpool---oil and brakes, oil and brakes plus a few starters, alternators and such. Thanks for the help--when I get to the sensors I will ring you up!

 

ok, now I feel somewhat frustrated, and, well, stupid. I searched my x300 manual--looked online, and hhmmm---how exactly do direct ignition coils work? Are there no spark plug wires--as found on american cars? I thought it strange yesterday after I pulled the cover and looked at the coil tops with those thin low voltage wires leading to them. Don't think me too daft---what am I missing here?

 

Scott:
Ok, now we are on the same page!- The wires you see under the cover are the primary, or power input wires to the coils. Instead of one coil and a distributer to "distribute" the spark voltage to the 6 plugs, each plug has its own coil. The ECU reacts to pulses from the CPS on the front of the engine and fires each plug's coil at the right time. With me so far?

So, my comment that you need not worry about the wires under that cover is because they operate at 12 volts, and as long as they are reasonably dry, will not hurt the spark the way a leakage on the high voltage side would. remove the coils bolts and carefully pull up on each one (after disconnecting the primary wire) and theres your plugs- wallah!!! How we doing ?

 

I'm with you Sparkenzap--actually a pretty ingenious system. Now my only question is what is the safest way to test a coil? As I change my plugs I want to test each coil to make sure it is good to go. I will also check the boots to make sure there are no cracks, splits, or damage. I think I will just go with champion plugs and new gaskets all around. Thanks-----Scott

 

Unfortunately there is not a good way to test a coil without sophisticated equipment- You can scope the input current with an oscilloscope, but I don't suppose you have one of them in your toolbox, right? Usually, when the finally gets bad enough to be missing regularly, you can swap around with a new one to find it-
But, back to your codes, The codes you listed could POSSIBLY be from a coil, but that wiould not be the first diagnosis- Have you reset them and then driven for a bit? And what drivability issue do you havem, now that you have it cooling?

 

Driving today I didn't really notice any big drivability issues. Idle seems a little rough every once in a while and when you start the car it catches then the rpms do a serious drop for a couple of seconds and go back to where they should be. I have had no dash lights since I reset them them with the code reader. I think I will just change my plugs and call it good. Though I am going to check out my o2 sensors when I get the chance.

 

Don't worry; Be happy!

 

I'm trying to be happy---but----I pulled in my drive today and the car stalled--battery and transmission light came on. Car fired right up and transmission engaged correctly. The stored code was P1314 "misfire rate catalyst Dama9e Fault"---any ideas? I'm starting to think I may have a cracked spark plug boot that is causing a mifire, but the stalling and the battery light confuse me. Last time the car stalled the windshield wiper fluid light came on so I think a short of some kind is causing the ECU to just throw different lights on. I am going to check the boots this weekend as well as other harnesses for breaks of any type. My battery is brand new. Thanks--------Scott not so happy

 

Scott:
check the power terminals at the firewall on both sides. Check the engine ground strap. for tight. You might see if you can find a cps for cheap.

 

Sparkenzap, I will check the terminals and I had considered the cps---question----do I have to change the ring gear or can I get away with just changing the cps? Also, where is the engine ground strap located--I.m sure I can find it, but just to save me groping around? I owe you a beer sparkenzap. Thanks---------Scott

 

No beer yet, wait till we find the problem! I have never heard of a bad ring gear, but there are plenty of reports of intermittent cps failures, although your symptoms are certainly not an exact match.

 

Sparkenzap---I checked the terminals at the fire wall and sure enough the ground on the drivers side firewall that runs back to the fuse box on the drivers fender was rusty and was not tight--tighter then finger tight, but wrench loose. I cleaned it up and tightened it down. The terminal on the passenger side was clean and when I put a wrench to it I was able to tighten it a bit. The fuse box on the driver's side fender contains fuses and a relay--I'm going to check what the fuses and the relay do--that may have caused a failure. I still want to do the cps and I'm wondering about the o2 sensors due to the fault code I got. Bought some spark plugs today, but I'm going to have to order the coil gaskets. It would be nice if the solution was this easy. I will do some driving tomorrow and see how she is. feeling better-----Scott

 

Scott:
Great- Only, BE CAREFUL! Those ain't grounds. They are main " bus connections. Short to ground with your wrench and you will get a BIG spark.

 

Ha ya I kept thinking disconnect the negative side of the battery.....disconnect the....wow---spark show---and I damn well know better! But anyway..took her out for a spin around town today and she seemed to run fine. A slight miss I suspect. I have the plugs so I may go ahead and change them and just go back and do the coil gaskets when they come in (it would be quicker if I actually ordered them). I'll see if she stalls at all this week---thanks for all the help Sparkenzap---you give this forum a good name, I'm going to nominate you for the whole jag master thing when the mods get that going. 4 gold stars and a cold pint for you-----Scott

 

Again, save the kudos until we have this thing running like the fine car it is. Misfires and stumbles are HARD to find on the XJ6...