The first 90 F degree days here in MN have my 97 4.0 XK8 idling with an irregular roughness or jerkiness, especially when in gear. It's not constant, it just misses or stumbles erratically. It also stumbles when accelerating moderately, though less so when you punch it hard.

I realize now that it has done a little bit of this since I got it last fall, just at a much, much less noticeable level, so I thought it was my imagination.

No codes. It seems negligible or absent when cold and quite noticeable/bad once the engine is 200 F degrees or more. I checked the fresh air intake and that all seems well sealed. I also checked the air filter and spray cleaned the MAF while I was in there.

I'm thinking that my next logical steps are replacing the spark plugs which look like they might be original (88K miles, it had NGK PFR5g-11E, I will go with the larger gap, PFRG-13E on the new ones) and probably getting a new coil pack to try swapping on each cylinder.

I'm assuming that aftermarket, non-OEM coil packs generally aren't reliable long-term?

My questions:

1- Does that seem like the logical next step/thing to try?

2- How does one go about getting the little bolts off the coil cover on the left-hand side (when sitting in the car) of the engine. I got the front 2 out with no problem but the middle bottom one seems impossible to get a socket and ratchet onto because it's too close to the strut tower. The right hand side was similar but far enough away form the strut tower that it worked OK...

The rear 2 bolts are also looking pretty tough on the left side... Any tips?

Thanks!

 

Start with fuel trims (LTFTs) - see the many threads about them.

Throwing parts with little data is slow and costly.

 

Use the torque app or similar and read the intake air temp and coolant temp from cold to fully warmed. See that those numbers represent well.

 

Red, you should be able to get to the bolts with the smaller 1/4 inch ratchets. As I recall you just have to find a low profile combo. I wish I could remember better how I got the one in the rear. Could it be finger tight? Then you could just use the attachment without the wrench if it won't fit.

 

The Check Engine Light (CEL) finally popped on today and threw 2 codes: P1314 and P1316 both are labeled as cylinder 8 misfire codes in Dash Command. So I'm thinking that means coil pack #8 (left side rear under the coolant reservoir I believe) is the likely culprit.

The fuel trims didn't look too funky from what I've skimmed about fuel trims since last night: ST mostly 0 to -6 and the LT mostly between +3 and +4 but sometimes climbing to more like +5.5 when the engine was at it's hottest (about 214-217 F). The LT is rarely negative.

As for the coolant and intake temps, I guess I don't understand what would be abnormal... Both start at a little above ambient temps and climb smoothly to absolute maxes of about 217 F on the coolant and about 160 F on the intake when not moving (intake is closer to ambient temp+5-10 degrees at freeway speeds).

Johnken, I will look into finding a shorter socket or something. Meanwhile if anyone else has tips on getting those rear 2 and bottom center bolts for the coil cover out on the left side out, please chime in.

Oh and for the coil pack, is the prevailing wisdom to use the only a new OEM Jag (Denso) LCA1510AB (2 wire) like what's already in there, as aftermarkets will fail relatively quickly? Or have people had good luck with aftermarkets coil packs?

p.s. I think that's maybe the first time I've ever actually been happy to see the CEL come on.

 

Best to use OEM coils. Any aftermarket ones, I've only heard bad, they go out sometimes in a few months. Leave the aftermarkets to a Honda. But do fix ASAP, so to prevent raw fuel dumping in cats and killing them. Seems the back 2 coils on left side tend to fail.

 

I ordered an OEM one and it's on its way.

Offhand, does anyone know how long it takes for a non firing cylinder to damage a catalytic converter? Is this a "use-the-other-car-till-it's-fixed" thing or a "get it fixed this month but keep driving it" kind of thing?

 

Ohh raw fuel can kill one of the cats in just a few miles! Then your looking at some SERIOUS cash to pay out. If you ever get a blinking check eng light. Stop ASAP and tow it.
I got mine cuz of a bad cat, so it was a great price. But I had the cats and all sensors from a totaled '05 (no not legal to do in CA, but ehh) Guy drove it for only 5 miles cuz 2 coils went, just to get those fixed at mechanic, and that ruin 1 cat. Sad thing (for him) was that the car was otherwise babied.

 

Thanks, I'll remember that if I ever see a blinking CEL on a Jaguar.

 

I suspect it (Dash Command) is wrong.

Have a look at the Jaguar meanings to make sure but from what I can see they do not imply any specific cyl but do mean severe misfires causing actual cat damage.

 

Good point, jagV8. I looked at the Dash Command again screenshot I took again and I was reading it wrong. D'oh, the descriptions are just below the codes rather than just above.

There's another code, P0308 (labled cylinder 8 misfire), listed above each of the other codes.

 

Ah. Cyl 8 it is then.

 

I found a funny little ratchet/wrench thing at Harbor Freight that has a much lower profile and worked great for getting those coil cover bolts that I could fit a normal ratchet on to very well because of tight spaces. Probably not good for anything requiring a lot of torque though.

Anyhow, once I had the right tool, I found out that 2 of the 3 bolts I couldn't get at (and one other bolt) were already stripped. Or more correctly the little knurled sleeve thingy with the threads in it is stripped out of the valve cover (see photo). It's the 2 rear bolts and the top middle one

Short of replacing the entire valve cover, what would one typically do about this? Is there some kind high temp epoxy to glue the little thread selves back in, just live with it, or use some kind of silicone dense to glue down the the coil cover a bit? or...?

On a side note, are the valve covers plastic?

Feeling confident that this coil failure is because I had a little coolant overflow out of the coolant tank by accident when the water pump failed on me. The poor seal must have let some antifreeze in to the #8 spark plug/coil well.

 

Sounds plausible.

 

Great design isn't it?

I used JB Weld (the high-temp variety) to good effect. Clean the hole and the ferrule and smear a little around both. You may need to tap them in to get the top flush, but go gently as the cam cover is plastic.

I can't remember the torque figure for those bolts, but it's pretty low. I nipped up with just the socket (no wrench).


HTH,
Mike

 

Classic cause for a bad idle is an intake leak, which is easy when the plastic intake components cook and crack in this car. Coil usually worse under load (but they can act weird when dying) Any air getting in between the MAF and throttle body will do this, makes the computer set the wrong mixture.

When I've had an intake leak, the car will miss like crazy, could throw misfire codes. Also I get 'restricted performance' on the dash.

Good luck.

 

It was the coil pack. I replaced that with a new OEM coil pack and put in new plugs (NGK Laser Platinum), she's purring like a kitten now and seems slightly faster.