NOTE: I mis-titled this thread, it should be "P0306 & P1313 Cylinder 6A Misfire"

Hello Again!

So I finally got through another round of preventative maintenance on my XJ12 while also chasing down a rich running issue. So far I think I've got the rich running addressed, however I now have a consistent misfire on cylinder 6A. To note, when I took delivery of the car, it would intermittently have a little bit of a shaky idle and was never quite as smooth as legend suggests which I contributed to the IACVs. But now it's consistent so I think it might be something a little bit deeper than that. So far I've replaced:

• All 12 Spark Plugs with NGK BR6EF gapped to .025
• All Spark Plug Wires with Karlyn/STI wires (OEM ones are not available anymore)
• New Denso Coolant Temperature Sensor (Jaguar OEM was on backorder and 3x the cost)
• 2 New OEM Coil Packs
• 2 New OEM Idle Air Control Valves
• 2 New OEM MAP sensors
• New vacuum lines to MAP sensors and fuel pressure regulator
• Had all 12 Fuel Injectors tested and cleaned by SD Faircloth along with Fuel Rail Crossover pipe replacement

I buttoned it up last night but after doing so it ran horribly and threw P0306 and P1313 indicating a cylinder 6A misfire. Sure enough pulled the plug and it looked brand spanking new with no carbon build up unlike 6B. In a quick ditch effort I tried throwing another spare spark plug wire back on but it didn't make any difference. I also checked the fuel injector connector like what was mentioned in this thread for a 1B misfire with similar codes, but mine appears to be fine. So far I've replaced every item indicated in the p0306 fix flow chart in the dealer service manual and have now made it to "Call Jaguar Service Hotline" line item. Any suggestions on what to look at next?

 

why did you fire a parts cruise missile

take everything off start over

 

Well, I had a couple of Map Sensor and IACV codes come and go and figured it'd be best to replace them when parts are still available. I replaced the coil packs and ignition wires since they were original to the car and were clearly a bit old. Coming from the Volvo world, I wouldn't call that a "Parts Missile", but more of a baseline "Stage Zero" maintenance run through of old and worn parts.

When you say take everything off and start over I assume you mean just to take it all apart and put it back together again?

 

Have you opened up the ECU(pax side behind plastic panel) and looked for any solder ring breaks on the back of the PCBs or leaky electrolytic caps? I recently opened mine up. They have the brown nichicon caps you want to keep an eye on. Mine were all fine but sometimes these leak out and destroy traces and cause all sorts of issues. Be careful when you lift up that top board. There are two ribbon cables that are not as flexible as they should be. I resoldered the connections on them after putting it back together as I found a few signs of stress on the back of the PCB that I might have done when lifting it up to take a look. Or they might have been there already. Also try not to short any of the wires when your re-soldering. Last thing you want to do is clear out the memory of one of the memory chips.
I also checked the TCM board since it was right there next to it. I found some soldering issues around an EEPROM chip that definitely needed attention see photo

.

 

I have not gone near the ECU. Frankly, I do not think I'm electrically inclined enough to open that up to check that for fear of introducing new issues.

 

I can respect that decision. I wasn't too keen on openeing mine up either. But I am concerned though that these caps are starting to get to their useful life age on our cars and these modules need to be watched. Specially the ones in the engine compartment with the heat these engines generate.

 

I might consider springing for a ECU rebuild if indeed that is the issue. My roommate (Master Volvo Technician) suggested it might just be a faulty plug. I'll try that this evening and report back. I think I'll also refer to the Electrical diagnostic manual and use my multimeter to check connections to the coil pack and ignition amplifier. If I cant come up with anything there, I might just ship the car out to California for a leave of absense at my parent's house along with a visit to our trusted Jag mechanic there.

 

To clarify, is your idle now consistent or consistently shaky?

My car has a bit of a lumpy idle. I want to say it's probably injector balance or spray pattern, so I would like to know if it's worth my while to get them cleaned.

 

It's now consistently shaking due to the misfiring cylinder. Previously it was only slightly lumpy around 30% of the time. The other 70% it idled so smooth sometimes I thought it wasn't running.

I dont think it was caused by the injector cleaning or spray pattern. The reason I say that is the report back from the rebuilder (highly reputable in the community btw) was before cleaning, they were already very good to begin with. I still went ahead and had him clean them and install all new seals and pintle caps. I just wanted to remove those as a potential factor and have my old, fire hazard, cross over pipes replaced. In short it dont think it helped or hurt it, but for 300 bucks all in, a little peace of mind reducing the likelihood of an engine bay fire was well worth it to me.

 

Other than checking the ECU connectors for corrosion, it is a bit early to dig into it. First try another spark plug or swap it, if no change swap the ignition coil packs and see what happens. Your good idea to check connections between ECU, ignition amps and coil packs. Apparently all went well with your parts "deployment", except for 6A.

 

Update:

Changed the plug for a new one, swapped coils, and took some contact cleaner to the coil pack connecters and ignition amplifiers (they both looked perfectly fine, but it couldn't hurt right?). No dice, still misfiring on 6A.

That being said, this time when I pulled the plug, I noticed it was bone dry. Threw a noid light onto the connector and its lighting up just fine so possibly the injector itself didn't react well to the service or got damaged in being shipped back. I'm still not certain if its getting spark though so I'd like to rule out the ignition system for good before ordering a new injector. Any recommendations on checking that?

 

I also took a peek at the ECU. Didn't take any connectors out, but there is zero evidence of water intrusion and looks way nicer than the used ones I've seen up for sale. Being a 41k mile car thats been garage kept its whole life in dry states, I highly doubt corrosion in those connectors is the issue.

 

inline spark tester

 

Progress has been made. Inline spark tester confirmed I have spark! Therefore, the injector is likely bunk. Guess I'll be calling SNG Barrat tomorrow to see if they can get it to me before I move.

 

Did you check impedance of the suspect injector? Spec is 13-17 ohms.

 

Just checked it. About 15.5 ohms and other injectors on that bank are about the same. Odd...

 

Hey someone correct me if I'm wrong, but a misfire on one cylinder code happens when the engine runs rough. And its usually the same cylinder Code. Doesn't necessarily mean its that cylinder just a rough running engine. You have cleaned out the throttle bodies well right?

 

Yeah cleaned out the throttle bodies, but in terms of the misfire, it has to be that cylinder because the spark plug comes out totally clean with zero deposits where any of the others will show deposits/use. I have read of people getting injectors cleaned and them sticking shut if that sat for a few weeks after the service. I'll get a 9V battery on it tonight to see if i can get it to "unstick". Last time I ran it I touched the injector while it was running and didn't feel any pronounce pulsing so I'm thinking it's likely stuck or dead still.

 

I follow a guy's channel called M539 restorations. He was doing a restoration on an a B7 Alpina engine, sent all the injectors away to be refurbished, spray pattern perfect etc. Came back and the engine ran rough and was getting codes for injector faults. Swapped in all new injectors rather than waste more time and it ran perfect. Maybe it's a little hit and miss on these injector refurbs.

 

So I tested the injector with a direct 9 volt feed. It is clicking as usual so on paper its technically okay. However, I took several hours this weekend to swap the injector with the one on cylinder 1A. The misfire code moved over to that one and installing a brand new plug on 1A returned no deposits so its pretty safe to say that the injector is bad.

Unfortunately, the injector is on backorder with no ETA from Jaguar when it will be available again...Does anybody have a good one sitting around?