Purchased a used 2005 S-Type 4.2L at the beginning of the year. It had a few ignition issues (had been sitting for several months prior to purchase, no idea how often it was started), but after replacing 2 of the coils (cylinders 1 & 4), and running a few tanks of Techron through it, it was running fine. 3 weeks, not a single code reported, passed emissions inspection just fine.

Then Friday night it started running a bit rough (fuel tank was half full). Started it on Saturday, and it wasn't really driveable. Rough idle, and when attempting to accelerate, the transmission seems to be shifting irregularly. Seems like it's downshifting (RPMs go way up) and then upshifting (RPMs are back in normal range) at will. Worse when accelerating or going uphill. If I can reach a steady speed in 3rd gear, it's much better. I think (HOPE!!!) the transmission is a symptom caused by the misfires, not the problem, as it has a rough idle even when in park.

I've got Torque on my phone, connected to the OBD2 port via bluetooth. At the moment I'm gettinga P0300, P0301, and P0304 fault. I've also got pending faults P1316 and P2099. The 2099 seems strange, since apparently that's bank 2, and the misfires are being reported on bank 1.

As I said, I'd already replaced the coils on cylinders 1 & 4. Pulled the plugs (which looked OK) and replaced them too, just to be sure. No improvement.

No idea where to go now (and with the closest Jaguar dealer over 20 miles away, it'd need towed if it's something I can't remedy myself). Battery is supposedly "new" and seems to be holding a charge well. Was running perfectly for 3 weeks, and then overnight, blam...

Here's one of the plugs I'd pulled, the other looks the same:

 

Jaguar uses an unusual designation for cylinder numbers.

Cyls 1 and 4 on a 2005 4.2L V8 are the front cylinder on the right side of the vehicle and the 2nd from the front on the left side of the vehicle respectively.

This is from the driver's perspective, looking forward.

 

umm, it's the standard nowadays (though maybe not in some smaller parts of the world?).

 

GM, Mercedes and Chrysler use front left as cyl #1

Ford and BMW uses front right.

There are some exceptions.

Hardly standardized.

 

Here is a link that shows the Jaguar cylinder numbering. http://www.jagrepair.com/images/AutoRepairPhotos/SDS002_V8_cylinder_numbering.pdf

 

If you're right, they're just not following the standard (or we're not understanding the standard - been a while since I read it!).

 

Actually, this might be a huge help. Somehow, when I originally googled it, I found the chart with cylinders 1,2,3 and 4 as the numbers on the right side. I guess it didn't note that that was only up to 2002.5 model years (or somewhere along the way my mind's been fried). I definitely didn't change out the 2nd one back on the left side (which according to the above chart should be cylinder 4). Hopefully I'll have time in the morning before I leave for work (it'll be just about dark when I get home today) to swap in a new coil and plug and see if that helps.

 

Fingers crossed!

 

Couldn't wait. Fighting the encroaching darkness, I pressed onward and inward. Either it was the gathering gloom, or I was smarter the last time I took the left side plastic cover off which is over the coils and plugs, I had a heck of a time getting it out of there. Maybe I disconnected something to get it out last time when I could see what I was doing?

Anyway, swapped in another new coil I had on hand, and one of the plugs I pulled on Sunday. Seemed to be idling smoothly. Revved it, let it settle back down, and it wasn't misfiring like it was all weekend. Cleared the fault codes, let it sit running for 15 minutes, nothing when I came back except a P1000, which should go away once all the drive cycles finish. Still haven't taken it out for a road test (I'd rather do that during daylight in case there are any issues), but it seems to be a vast improvement.

Not sure if I should feel relieved or stupid, I was practically pulling my hair out all weekend trying to figure out what else could be the problem. Now, of course, I'm hoping that it's not just another temporary fix for an underlying issue that will return later. Think I'll finish swapping out the plugs on the other cylinders tomorrow, the ones I've checked don't look bad, but there's no telling how long they've been in there. They're Bosch platinum, so I don't think they're the originals, but at 124,000, I've no idea how long ago they were changed. I'll post an update once I get a chance to take it out on the road...

 

Okay, filled the tank, drove to work, no apparent issues (forgot to scan it when I got here, I'll check after the drive home). Seemed to run fine, both at highway speeds and in stop and go traffic. Since it possible had 3 bad (or going bad) coils when I got it, I'm wondering if I should replace the other 5 as a preventative measure, or wait until I have issues with them. The ones in there don't appear to be OEM, so I'm assuming they were all changed at one time or another before I got it.

I "thanked" everyone who responded. Without the smack in the head about cylinder numbering, I'd still be pulling out what's left of my hair...

Now if I could just figure out where my coolant is leaking from, I'd be good. No apparent visible leaks, at least from the top (haven't been underneath it yet to check). Not dripping on the ground, but after a drive at highway speeds, you can vaguely smell antifreeze when you get out and walk by the front of the hood. Takes about 2 weeks for it to run from full to where it's tripping the warning light/message, I've been topping it off once a week and it's been fine. Seems to just get to the "low" indicator inside the overflow tank in a week's time. But I suppose that's a topic for another thread...

 

It tends to leave a pink/red stain so a good light and peer around. Borescope (one of those little USB cameras with a light) may help.

 

Most such "mystery leaks" are a small crack on the expansion tank nipple on the cap-neck, usually on the underside of the nipple where it can't be seen. Less common as a mystery, but perhaps more plentiful though easier to find, are the plastic "turret" on the upper rad hose assy, though I'm not sure if the V8 has those? Lastly, if you are at or beyond 100k miles, have a look at your radiator, back side, lower right. May have to pull the undertray and put it up on ramps and lie underneath while its running to find it...but they can drip sporadically, you get the smell, but it usually dries on the undertray before it ever finds its way to ground. The leak occurs about 1/3 of the distance from the bottom, at the interface between the plastic side tank and the aluminum headsheet.