I have had this ongoing problem for over a year now. The mechanic shop said the diagnostic code indicated one of my coils was bad. They replaced it and seems like the problem was gone but only to return the next day. I took it to another mechanic who replaced a second coil but still no results. I put in new plugs and a new O2 sensor and cleaned the fuel injection system. No other error codes are coming up but I am still experiencing an intermittent shudder (more like hiccups) when idling about every 8 seconds or so. Seems to be worse now in the summer? Does anyone know what can be done about this?

 

Classic misfire symptoms, my money's on one or more of the other coils.

 

mine does it too it use to cut off completely, untill i had it fixed. I will try these coils, what are they exactly called and how many do i have so i can replace them.

 

They're called ignition coils. Each spark plug has it's own coil, once they start to fail they only get worse, eventually the check engine light will flash during the misfire, ultimately it will get so bad the check engine light will stay on. Reading the codes after the flashing CEL should reveal the guilty cylinders. Many people recommend changing them all, but I had a code for cylinder 8 only, I just replaced that coil and all was well.

 

For some reason, the cylinder numbers often get misdiagnosed by mechanics not familiar with jags, if this is the case. Secure the code yourself, and consult the Vehicle Specification Document on our FAQ threads (I know for sure the XK8/R forums have it, which shows bank/cylinder identifications)

You could swap the new coil into all cylinders, trying to find the bad coil...and assuming its ONLY one (I say this, because they often go in succession if not replaced immediately), or you could replace them all with new ones...though that is the costlier option...but quicker to resolve.

 

Be aware that coils are a wear item. Changing them one by one will insure continuing problems. If you have not done so change all 8 coils. Also check carefully for oil in the spark plug wells. You may need to change the valve cover gaskets too. If you have a 2000 year model and don't know the history you will be ahead to change all 8 plugs, 8 coils (don't forget the boots too if they don't come with the coils!) and both valve cover gaskets. Please use the factory spark plugs and not some after market stuff!! This has also caused many problems.

It is not easy to determine when a coil is causing random misfires. It got so bad that Ford came out with a coil stress tester for their dealers. Even then the dealers did not use them properly and still were missing the random misfires from the coils. Ford eventually gave an extended warranty to the LS owners of 10 years and 100K miles for just the coils and plugs. I had my 2003 Lincoln LS fixed under this extension. Got 8 plugs, 8 coils and 2 valve cover gaskets all for free and the car had 77K miles on it. I was very pleased and surprised that Ford did the "right" thing!!!

When you cleaned the fuel injectors hopefully the fuel filter was also changed? It's easy to miss because it's a bit of a pain to change.

One last thing. It's very easy to have what you think is transmission problems when it's really misfires causing the transmission to act up.
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Geez I'm glad you asked that question! Every once and a while, I also get a shudder when my car is idling. It only happens once maybe every couple of weeks, but it's noticeable when it happens. I'll have to take it in and have the coils checked.

 

Another cause of idle problems is an air leak but usually the problem occurs all the time.

Get a $25 (ebay) elm327 OBD tool and check:
all the supported monitors are Complete
that the car runs CL (closed loop) on both banks
any codes (don't clear them yet)
any pending codes (don't clear them yet)
the fuel trims at idle and at 2500rpm
the O2 sensor signals BUT how to do it depends on the MY (model year) of your car

BTW, the cylinders are numbered differently depending on the MY. It's in that Vehicle Spec pdf I posted.

 

Whatever you say about diesels, this problem's impossible.
Leedsman.
And yes, I know there are other problems...

 

Er, diesel is an irrelevance as no-one with problems on the thread has a diesel. (But yes they do have their own, especially the turbos and DPFs, not to mention the heaters.)

 

Hi guys,

I'm also chasing a misfire, and so sympathise with your plight 'florita1216', and was wondering if one of you guys could tell me how the cylinder numbers from an OBD2 scanner should be interpreted.

I've looked at a pdf posted on here which shows the MY vs cylinder number (i'm guessing the one posted by 'jagV8'. BTW many thanks for the info.) It's just the scanner simply talks about cylinder numbers (e.g. 1 and 3 for mine with potentially bad coils) without mention of a bank.

Just wondering if this means the scanner is using the convention adopted post 2002 (what i always thought of as the classic american V8 numbering convention, which i always thought made a lot of sense).

Many thanks

Alex Boxley

1999 XJR

 

It's the engine management that decides how cylinders are numbered not the scanner, so cylinder 1 and 3 are what Jaguar said they were in 1999.

 

True!

Just bear in mind that a code for a misfire on cylinder X is the PCM's way of saying it APPEARED to be X. The fault MAY be elsewhere.

If you read up how the PCM detects a misfire, this makes sense. It's one reason why people often change multiple coils (and/or plugs).

ALL codes should be considered as HINTS. Someone (that's you!) has to figure out how good each hint is.

 

In the good old days(?) when I used to run petrol cars, they had ONE coil and a rotating high-voltage distributor. I can't seem to remember much trouble with the spark coils, (they were about three times the size) although other things could go wrong in the high-voltage area such as tracking -- but you could see that before your very eyes... And yes I know all about maintaining the high-voltage during peak revs. in an 8-cyl engine, but there are better ways of achieving that aim than the plethora of spark coils that seem to be a continual source of trouble; and not just in Jaguars -- other make-specific websites I've used indicate multple spark coil problems same as here.
Leedsman.

 

Thanks guys, nice to know which one dictates cylinder numbering.

So without a bank number is there any way of determining which 'cylinder 1' is is, as jaguar thoughtfully gave it two. Going to try swapping the coils about, probably move all up one or swap odds and evens.

Will the car detect if the plug to the coil is pulled while the ignition is off as if it will that could prove a cunning way of fault chasing.

Just a final though, having taken your advice and looked up how it detects misfires could my seemingly erratic misfire messages be a duff crank position sensor? Any cunning way to test this?

Thanks in advance

Alex

 

The COP (Coil On Plug) ignition system is head and shoulders better than the old distributor and plug wires. It's not even close. That's why there are NO cars left running a distributor.

Be careful about pulling a connection in the ignition circuit. If the circuits are not grounded you can cause feedback and possibly blow something else out!! Swapping coils when you don't know the history is usually just a bit of wasted effort. After a certain amount of miles or time the coil will start to weaken and you will end up chasing your tail. Swap them for trouble shooting reasons but with older cars just replace all of it.
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ABoxley - do you actually have an S-Type? If not, you REALLY want to be asking in the right section!!

For the S-Type, there are NOT two cylinder 1's for OBD.

 

I replaced all my coils this past spring, as well as the transmission fluid, and all other filters and fluids. World of difference on my 2000 s type with 52k on it

 

I do feel a tad red in the face 'jagV8' as I don't have an S-type (currently not driving around in an XJR) so i'll repose the question in the XJ8/R part. Thanks

Just wondering though if in your opinions the crank sensor could be the problem as they are about £45 rather than £640 for 8 new coils, as much as i'd love to splash out all the cash i could on my 'R i currently can't afford it.

So for anyone else in my position is there a cunning way to test coils (i recall someone on here mentioning a coil tester being used as coil failure seems to be a relatively common problem, would this be a dealer only device or would specialists be likely to have one.

Many thanks and i'll be off to the XJ section.

Alex

 

There's a good chance the jag docs show the XJR cylinder numbering for OBD usage. A very good chance. They do show it for S-Types. I'd hunt with care through the docs.

You could swap sensor this and sensor that and then who knows but it's not the way to go, really. You could spend a ton of cash but not fix the problem. A good tech sounds useful.

Coils are notoriously hard to test. (Though the car does it really well. Expensive test gear!) I'm struggling to believe they're £80 each. Could you maybe fly them in from the USA for less? But more data so you have better clues to the fault looks desirable or a tech who knows the car (XJR and/or XJ in your case).