Please bear with me, a bit of a long story. This is related to a 2008 S-Type 3.0 with 175k miles. I am a shade tree mechanic, and this car belongs to an 82 year old friend/neighbor. He had a radiator hose blow a couple weeks ago. Drove home several miles, car got hot but according to him did not overheat. I looked at it the next day, topped off with some water to identify leak location. It started and idled fine (no coolant in the oil and no oil in the coolant) but never put it in gear and never drove it, identified blown hose and another hose with pink crusty crap at the joints. Ordered and replaced both. One had 3 locations, the reservoir, the heater core and the water pump (probably irrelevant). The other hose was the one with the metal flange that connects to the intake manifold and the other end to the upper radiator hose. This is where the problems arise. In order to remove the flange the electrical connector to the #1 fuel injector needed to be unplugged to access one of the bolts. The connector was held in place by silicone as the retaining clip was broken. I found it like that and it had been like that for at least 1.5 or 2 years as the car had not been in a shop for that long. My neighbor moved to Florida from California about a year ago and the car had been running fine with this connector held in place with a dab of silicone. I unplugged the connector, replaced the flange, and plugged the connector back in. First, I thought zip ties may be better than silicone. Car idled ok for a minute, I started to back out of garage to take for a test drive to get it up to temp, within a minute got reduced performance message, was running rough and got codes for cylinder 1 and 6 misfire. :-(

I played with more zip ties, figuring it was not making good connection, nothing worked. Gave up on zip ties, went back to silicone, still getting misfires. Last night I replaced the connector (bought pigtail, but just used the connector and de-pinned and repined to original harness. it was a total pain as there was almost no slack in the wires. After some colorful adult language I managed to replace connector and it seemed to idle just fine. As soon as I put it in gear to take test drive it started to idle poorly. I ran over a dozen code read reports clearing codes in between. Sometimes despite idling rough there were no codes. Other times it would eventually throw mostly #1 cylinder misfire code, but some of the report it was also have random misfire, and cylinder 6.

After it warms up the misfire is worse and more frequent. When cold and running at about 1k rpm it seems ok, as it warms up and the idle drops the misfire gets worse and worse and when you put it in gear (creating load) it gets even worse. I had to remove the intake air pipe to replace the hose and I am concerned about a vacuum leak being the culprit, but that doesn't make sense with the consistent #1 misfire with code P0301. I used a noid light to confirm injector 1 electrical connector was getting the signal to fire the injector both before and after repining. All signs point to an issue with the injector on cylinder 1, but now that the connector is "fixed" I dont know what else it could be that makes sense.

Obvious possibilities are vacuum leak (but I would think misfire wouldn't be concentrated on #1) coil, plug and injector. I dont want to pull the manifold to replace coil and plug as I dont think that they would be bad out of the blue, the most obvious and likely is an issue related to the fuel injector. I assume it is impossible to do plugs and coils on passenger side bank w/o pulling manifold?

Thoughts please? Thank you for reading.

 

Have the spark plugs and coil units been replaced?

Has a compression test been performed on the cylinders in question?

Below is the cylinder numbering scheme for the AJ-V6:

 

The coil=pack on cylinder #1 will just barely clear the bottom of the intake manifold on the late 3,0 V-6. I have never removed the plug from this position with the intake manifold in place, so I cannot comment on that. The soft "caps" on the coil-pack are known for doing a lousy job of sealing the recess/spark plug well in the cylinder head and you may well have coolant surrounding the spark plug at the base. A look-see is warranted.

And, yes, coil-packs most certainly fail "out of the blue"; ask me how I know...

 

Yes with those high miles all the coils and plugs should be changed. It's time.
What scanner are you using? If you can post the actual error code. Be sure to clear all codes so you can see what ones return.
Jaguar's usually need an Icarsoft scanner if your not using the factory SDD stuff.

Your smart to change the radiator hoses but be aware the car in now over 14 years old and ALL the rubber hoses should be replaced.
Do you know about the DCCV? It's another cooling part that has a close to 100% failure rate and messes up the heating and cooling inside the car. Has that been replaced yet? If not it's a good time to do it when changing hoses as there are a number of cooling hoses attached to the DCCV that need to be disconnected anyway.
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I was able to resolve with a new coil pack. It may have been damaged by the coolant leak, nt sure but it is resolved. Thanks all!!