It went from bad to worse.

I installed the new fuel injector in cylinder 8. Started it up and as usual it ran ok cold. I let it idle and warm up while I made sure the injector wasn't leaking. The idle dropped down to the lower RPM like it does when its warmed up. Was still idling smooth.
I took it for a drive. Just like before it ran ok for maybe a mile. Then the same problem started with the miss so I turned around and headed home. It got worse the more it warmed up.
When I pulled into the driveway and let it idle I noticed a new symptom. Now there is a random tapping sound. Sound just like lightly tapping a screwdriver onto plastic. Not a metallic sound. And its coming from the cylinder 8 area. The ticking isn't in time with the misfire but almost random. It never did this before and today it didn't start doing it until after it was driven a while. I will let it cool and see later if it still does it when the engine is cool.
I disconnected the injector while it was idling to see if the new injector was making the noise but it made no change.
Doesn't seem to sound like the kind of noise a valve would make either but its definitely coming from up top and around cylinder 8. Its probably been a sticking or slightly bent valve all along. Anyone want a cheap Jag?


Dave

 

Yet another update:

I let the car cool off for 24 hours and started it again. No noises and smooth running. Let it idle about 10 minutes. The tapping on plastic sound started again. Almost inaudible at first and then it got louder and the louder it got the rougher the engine idled.
Turns out the noise is the sound of the coil arching! Disconnected it and the noise stopped. This coil has been replaced twice and the spark plug once. So either I swapped a bad plug with a new bad plug or I got 2 bad coils in a row or maybe BOTH. WTF?
So after it cools I will try swapping the coil a third time and see what happens. Maybe there is hope for this damn thing yet.



Dave

 

Finally figured out what the hell is going on with this POS.
I swapped all the coils one at a time into cyl 8 position and let idle until misfire occurred, usually less than five minutes.
Out of 8 coils, THREE of them fail in that hole. But only one fails in another cylinder after warm up. The reason more fail in that hole is that its buried and that part of the engine runs hotter so whatever is in that hole fails faster. The others when in other cylinders don't get hot enough to fail. The Denso that arcs and makes arcing noise fails in any hole after a short warm up. Somehow when I was swapping coils to troubleshoot earlier I managed to by chance pick one of the other bad ones and put it in cyl 8. The bad one in cylinder 8 fails first because it gets hotter faster. And I always shut it off once the misfire gets rough to not stress the cats unnecessarily. I bet if I let it run long enough the others would also fails in their holes after they had more time to warm up.
Here is one interesting thing - All 3 of the bad ones were on the same side and thats the side thats missing a coil cover. So apparently the covers do help and not hinder.
Fun stuff - not. So for now I am going to replace all 4 coils on that side and find a new cover. I have the old one but someone used the wrong screws and broke all the tabs off. A couple of the threaded brass things they screw into on the valve covers are missing on both sides also.
Many of the coil connectors are of course broken also and it seems Standard Motor S-1415 will fit but so far the cheapest I can find them is $20 each including shipping.

Dave

 

A friend had a broken connector on his 97. He used rtv to hold the wires in place and it's been working for a couple of years now.

 

Not sure if you mentioned. How hot is the engine running? I have a scan gauge plugged into the OBD connection. Temperature on these babies do fluctuate quite a bit and have a tendency to run warm. Rich


QUOTE=DaveInVA;1326000]Finally figured out what the hell is going on with this POS.
I swapped all the coils one at a time into cyl 8 position and let idle until misfire occurred, usually less than five minutes.
Out of 8 coils, THREE of them fail in that hole. But only one fails in another cylinder after warm up. The reason more fail in that hole is that its buried and that part of the engine runs hotter so whatever is in that hole fails faster. The others when in other cylinders don't get hot enough to fail. The Denso that arcs and makes arcing noise fails in any hole after a short warm up. Somehow when I was swapping coils to troubleshoot earlier I managed to by chance pick one of the other bad ones and put it in cyl 8. The bad one in cylinder 8 fails first because it gets hotter faster. And I always shut it off once the misfire gets rough to not stress the cats unnecessarily. I bet if I let it run long enough the others would also fails in their holes after they had more time to warm up.
Here is one interesting thing - All 3 of the bad ones were on the same side and thats the side thats missing a coil cover. So apparently the covers do help and not hinder.
Fun stuff - not. So for now I am going to replace all 4 coils on that side and find a new cover. I have the old one but someone used the wrong screws and broke all the tabs off. A couple of the threaded brass things they screw into on the valve covers are missing on both sides also.
Many of the coil connectors are of course broken also and it seems Standard Motor S-1415 will fit but so far the cheapest I can find them is $20 each including shipping.

Dave[/QUOTE]

 

Thats how most of these were held in from a previous owner. I also put heat shrink tubing over the exposed push on metal sleeve connectors that go on the pins in the coils so they can't ever short to each other.


Dave

 

The new AIP coils came in today so I replaced the 4 coils on that bank. Turns out the original problem was THREE bad coils. And when I swapped coils Good Ol' Murphy saw to it I put another bad one in Cylinder 8. Between that and the ECU "ONLY" flagging Cylinder 8 as the culprit it made it look like the problem was elsewhere. One coil always failed before the others on warmup. Then the other 2 would fail a little later explaining why it got so much worse the longer you drove it. The ECU may have eventually flagged the other 2 but by then I'd stop driving it.
When this problem first started my first instinct was to replace all the coils as they were original Denso's with 100k on them. Had I just went ahead and done that the problem would have been fixed 2 months ago but instead I over-thought the problem and went off in the wrong directions.
I will order 4 more coils and replace the other side also as those coils are likely not long for this world either.
Back a few months ago when the belt tensioner failed and it overheated very briefly (like seconds) while I pulled over right away and shut it off that might have been what put them over the edge.
The interesting thing is all 3 bad ones were on the same bank and its the bank with the coil cover missing. That must figure into it somehow.
I only took it for a 10 minute drive at 30 mph and under around the neighborhood but there was no sign of the misfires. No new codes either. Tomorrow I will take it out for further testing and the battery will be on the charger tonight even though I was amazed it hasn't gone dead sitting for 2 months and being started several times without long enough drives to charge it back up.
So if it passes tomorrows higher speed tests and some hill climbing to put it under load then I guess this can be called fixed.


Dave

 

Jaguar struggled with lousy coil suppliers on all of their models up until the 2004/2005 model years when they finally seemed to get it right. Our two Jaguars (both built in May 2005) have both done over 90,000 miles and we've never had a coil problem, knocking on elmwood....

The long-time members with the older models here will tell you to always start by suspecting the coils whenever ignition issues arise. Looks like your case may turn out to be another step in that direction....

 

I didn't have any coil problems until it hit 100k it seems. The Denso's must have 100k timers in them. I just wished I'd gone with my first instinct and replaced the coils right off and it would have been fixed a long time ago. I just never guessed I'd be dealing with THREE heat sensitive coils all at once. That and the ECU only complaining about 1 cylinder caused me to over think the problem.


Dave

 

I'm looking forward to your next report.

 

Is 100K when you changed the plugs?

(100K interval on my car but maybe less on yours?)

 

Yes, they looked original and some were really tough to get out but they all, even cylinder 8 looked entirely normal and usable. But they may have been at the end of their life anyways and stressing the coils. I changed the plugs as part of the misfire troubleshooting.



Dave

 

Just took the Jag for about a 45 minute drive in various traffic and speeds and so far so good. Only thing I see is that it is now idling a little higher than it used to after warm up. (about 750 ish vs 550-600 rpm). Not sure what thats about. But no misfires or codes. I will order and replace the other 4 coils as I am sure it will not be long before another Denso or 3 fails. I will also get another coil cover and screws as all the original screws for that side are missing and someone used the wrong ones and broke all the tabs off the old cover. Can't believe the cheapest I can find the proper screws is $8 each, maybe I can find some rubber washers to put under the regular screws.
So I guess this thread can be marked SOLVED. (Got solved in spite of myself anyways)


Dave

 

It's been a long battle. I'm glad you didn't give up on it, the information we have acquired will probably help another member some day in the not too distant future.

 

I hope no one else goes through all this just to find its the coils all along. Then again its my own damn fault for not going with my original instinct with the coils and over thinking it.
Moral of the story - If the ECU only complains about 1 cylinder don't believe it. And if your car has Denso coils with 100k miles on them replace them all and not just the suspect one.
On the other hand at least now I know the car has new plugs, really clean injectors (BG44k), the ECU is still good, no obvious vacuum leaks, new fuel filter, and the throttle body and MAF are nice and clean. And I learned changing the fuel injectors are easier to change than the spark plugs. I bet some Jag engineer got fired over that one.
Oh, and thanks to everyone for their help!!

Dave

 

Dave,

I am so pleased you got to the bottom of your P0308.

Gus
www.jagrepair.com

 

If it's idling higher, something's not yet right.

You can clear learned fuel trim etc values by a hard reset, and see if the idle relearns back to a lower value.

Or wait, and see if it relearns anyway.

If it stays higher, go troubleshooting. I'd start with fuel trims.

 

The ECU was given a hard reset along the way during all the troubleshooting but didn't notice the higher idle until after replacing the coils. Now that its been driven a little the idle seems to be heading back to normal so its likely just the ECU relearning things...



Dave

 

Just curious. What brand of coils did you get/recommend? And where did you source them from and cost ?
Was looking on Amazon at vanden plas brand of coils at$22.50, what do you think?

 

I got them from this Fleabay seller AIP. They accepted my offer of $21 each including free shipping. They sent them super fast, had them in like 2 days. Very happy with them.


Dave