S Type 4.0 2001 - misfire
Discussion
I drove the present Mrs B's Jag to work today and it running really badly. She told me it was lumpy, but it has a bad misfire. Starts fine and smooth when cold but as it gets hot it misses badly at lower revs as soon as it gets a load on the engine. It then shudders and at idle is not smooth. Last time I drove it a couple of months ago I thought it missed occasionally but this is much worse. It has only done 67k and is in fine condition for the age but I looked under the bonnet and couldn't even see the plugs, leads, coil packs etc, where are they? Any advice would be gratefully received as I can't take it to the Jag dealer, they charge £180 just to look at it!
Coil packs and spark plugs are underneath the rectangular covers running down the centre of both camboxes on the top of the engine. Sparkplug change is not called for on the service schedule until 70k on the non supercharged V8s so plugs may not be the problem, but it won't do any harm to change them to rule plug failure out.
You need to plug a code reader into the daignostic socket as any misfires should be logged by the ECU. You can buy small hand-held OBDII code readers from ebay for less than £20. They list any fault codes recorded by the ECU & you then go online to cross-reference the fault code with the list of Jaguar S-Type fault codes.
This allows you to pinpoint the exact fault & failed component with a good degree of accuracy.
I bought an Autel Maxiscan MS300 OBDII code reader for £18, as I had the yellow EML light on last year on my 2001 XJR. The fault was the front Oxygen/Lambda sensor which I obtained & fitted myself for a fraction of the cost a garage would charge. The code reader was then used to erase the EML lamp & the car has been fine since.
The ignition coils are very easy to reach on the AJV8-just undo the small bolts & remove the centre piece of the cam cover & you'll see them below. Each one is secured by 2 bolts, so when you disconnect the electrical plug & remove the 2 bolts, they pull off upwards easily. The spark plugs are directly underneath in deep recesses-shine a torch in to make sure no engine oil has seeped past the cam cover oil seals & down into the spark plug wells.
Also may be worth checking that the spark plugs are all screwed in tightly as well. Ignition coils can be bought cheaply from parts breakers off ebay for around £15 or less.
But before doing anything, either get the ECU scanned by a garage, or get a basic cheap OBDII scanner & do it yourself. It's quite easy & the hardest part is locating the 16 pin D-shaped diagnostic plug. On my XJR it's under the dash in the driver's foorwell, close to where my left knee sits
Good luck
Alex
This allows you to pinpoint the exact fault & failed component with a good degree of accuracy.
I bought an Autel Maxiscan MS300 OBDII code reader for £18, as I had the yellow EML light on last year on my 2001 XJR. The fault was the front Oxygen/Lambda sensor which I obtained & fitted myself for a fraction of the cost a garage would charge. The code reader was then used to erase the EML lamp & the car has been fine since.
The ignition coils are very easy to reach on the AJV8-just undo the small bolts & remove the centre piece of the cam cover & you'll see them below. Each one is secured by 2 bolts, so when you disconnect the electrical plug & remove the 2 bolts, they pull off upwards easily. The spark plugs are directly underneath in deep recesses-shine a torch in to make sure no engine oil has seeped past the cam cover oil seals & down into the spark plug wells.
Also may be worth checking that the spark plugs are all screwed in tightly as well. Ignition coils can be bought cheaply from parts breakers off ebay for around £15 or less.
But before doing anything, either get the ECU scanned by a garage, or get a basic cheap OBDII scanner & do it yourself. It's quite easy & the hardest part is locating the 16 pin D-shaped diagnostic plug. On my XJR it's under the dash in the driver's foorwell, close to where my left knee sits
Good luck
Alex
Really appreciate the help Alex, very useful info for someone more used to dealing with a simple RV8 engine. I will do as you suggest as this is the only way to avoid wasting money buying parts that are not required, better to know what is need, Thing is it had a slight misfire when it went to the Jaguar dealer locally and they never said a thing about fault codes and I am SURE the guy there told me the leads had been changed! Anyway, the code reader is the way to go so I am going to invest in one.
Many thanks for your very comprehensive reply once again.
Regards, Keith.
And to you as well NormanD.
Many thanks for your very comprehensive reply once again.
Regards, Keith.
And to you as well NormanD.
Yep, there are no ignition leads with this system-the individual coils are terminated at the bottom directly by the rubber sleeve which goes over the spark plug body. There are no connecting leads required as the distance is so short-the rubber sleeve has a spring-loaded centre contact so that when you push the whole coil assembly into place, the spring-loaded contact makes the connection with the metal connector at the top of the spark plug.
The plugs themselves can be a tight fit in the thread when attempting removal-a long extension bar turned steadily will unwind the plug, which can then be checked & the thread lubricated with a dab of WD40 to make refitting easy without thread tightness.
The plastic cam covers have rubber seals in their channels, and the 4 spark plug access holes in the cam cover each has a sealing ring around it-if these are damaged or showing signs of weakness, then you can get oil leaks around these seals which leaks directly down into the spark plug recesses. If you get too much oil building up it can cause ignition problems & misfires
If your spark plug recesses have excess oil in them, leave the spark plugs in place & dab a WD40-soaked piece of tissue down the recess with a long thin screwdriver to soak up the oil, before dabbing a dry tissue down the recess to dry it out.
But certainly investing in the OBDII code reader is a good idea-it's a basic device for less than £20 but tells you all you need to know. The only inconvenience is that when the device shows the fault code, you then have to go online to cross-refer to the list of fault codes.
These are in the format of 'P' numbers for each detected fault.
However, the system peforms checks at start-up & in various driving modes which throw up 2 specific 'P' codes that aren't actually faults-just process status indicators. You'll get code P1000 at start-up, which signifies that the ECU hasn't yet run through all it's specific checks. This will only happen when you've completed a drive which has various driving styles to it-such as steady state cruising or full throttle at higher engine RPM's.
Whenever you go for a drive, the system starts out with P1000 and checks the required parameters as you drive the car. If you don't drive the car in such a manner as to allow the ECU to check all the parameters-such as not using full throttle etc-then at the end of the drive you'll still get code P1000.
This is not a fault and is the normal way the OBDII Diagnostic system works.
If you happen to drive in such a manner which allows the ECU to test all the parameters for all engine speeds & loads, then at the end of the drive you should get code P1111. This means that the system was able to check all the required parameters & functions, and that no faults were found
It's not too difficult to get the hang of it & you can use the scanner to reset the orange EML lamp & erase all the stored fault codes. Then when you use the car again you can see if the same fault re-appears.
You can't damage anything by doing this, as any faults present will be genuine engine/system faults & nothing caused by the scanner. OBDII stands for 'On Board Diagnostics' & 'II' is the standard used on vehicles built after 2001 in Europe & from 1996 in the USA, which superceded the original OBDI.
The plugs themselves can be a tight fit in the thread when attempting removal-a long extension bar turned steadily will unwind the plug, which can then be checked & the thread lubricated with a dab of WD40 to make refitting easy without thread tightness.
The plastic cam covers have rubber seals in their channels, and the 4 spark plug access holes in the cam cover each has a sealing ring around it-if these are damaged or showing signs of weakness, then you can get oil leaks around these seals which leaks directly down into the spark plug recesses. If you get too much oil building up it can cause ignition problems & misfires
If your spark plug recesses have excess oil in them, leave the spark plugs in place & dab a WD40-soaked piece of tissue down the recess with a long thin screwdriver to soak up the oil, before dabbing a dry tissue down the recess to dry it out.
But certainly investing in the OBDII code reader is a good idea-it's a basic device for less than £20 but tells you all you need to know. The only inconvenience is that when the device shows the fault code, you then have to go online to cross-refer to the list of fault codes.
These are in the format of 'P' numbers for each detected fault.
However, the system peforms checks at start-up & in various driving modes which throw up 2 specific 'P' codes that aren't actually faults-just process status indicators. You'll get code P1000 at start-up, which signifies that the ECU hasn't yet run through all it's specific checks. This will only happen when you've completed a drive which has various driving styles to it-such as steady state cruising or full throttle at higher engine RPM's.
Whenever you go for a drive, the system starts out with P1000 and checks the required parameters as you drive the car. If you don't drive the car in such a manner as to allow the ECU to check all the parameters-such as not using full throttle etc-then at the end of the drive you'll still get code P1000.
This is not a fault and is the normal way the OBDII Diagnostic system works.
If you happen to drive in such a manner which allows the ECU to test all the parameters for all engine speeds & loads, then at the end of the drive you should get code P1111. This means that the system was able to check all the required parameters & functions, and that no faults were found
It's not too difficult to get the hang of it & you can use the scanner to reset the orange EML lamp & erase all the stored fault codes. Then when you use the car again you can see if the same fault re-appears.
You can't damage anything by doing this, as any faults present will be genuine engine/system faults & nothing caused by the scanner. OBDII stands for 'On Board Diagnostics' & 'II' is the standard used on vehicles built after 2001 in Europe & from 1996 in the USA, which superceded the original OBDI.
Green is good said:
Thanks very much for the info, very helpful. It supposedly received a full service a few months ago at a cost of over £500 and I think they changed the leads and plugs. So coil packs could be the cause I suppose. Cheers.
Bit late - but if you can confirm the plugs were changed?I'd look at them if your code reader points to misfire and see if they are NGK, as there has been a FAKE warning sent out recently.
Seems there are a lot of fakes out there and your symptoms could be plugs.
Good Luck!
Personally I would think if the plugs were recently changed that there is water in the coil area. Why?
It's a pretty common problem on S-Types. The water coming off the windscreen goes on top of the engine and works it's way through the coil cover and the moisture presence results in a misfire.
The fix is pretty simple - remove the coil cover, remove the coils and dry them out, dry the area around the plugs, dry everything else and reassemble with RTV placed where Jaguar recommend it.
It's a pretty common problem on S-Types. The water coming off the windscreen goes on top of the engine and works it's way through the coil cover and the moisture presence results in a misfire.
The fix is pretty simple - remove the coil cover, remove the coils and dry them out, dry the area around the plugs, dry everything else and reassemble with RTV placed where Jaguar recommend it.
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