X308 XJR lumpy idle/restricted performance
Discussion
Hi all,
I really hope someone can help with my late 2002 X308 XJR. After being stood for a couple of weeks I fired it up and soon noticed a quiet but audible ticking noise early in the rev range from the engine bay when the engine was under load. The car drove fine but soon restricted performance was shown. After pulling over and turning off, the car started back up OK with no restricted performance but the orange 'check engine' light stayed on.
The engine is slightly lumpy on idle, and the quiet ticking noise is still audible early in the rev range, but it drives perfectly smoothly/quietly/pulls strongly other than that.
The garage has pulled a lot of spurious fault codes out and are investigating. The plugs are apparently fine, and they have reseated each coil pack without noticing any difference at all so they do not suspect a coil pack.
There is no rattle at all from the timing chains, and my car is much later than the supposedly affected VIN's from Jag's bulletin...
The battery is testing fine for them too, I know that low batteries can cause a multitude of odd errors. I usually kep the car on a trickle charger but am conscious that it has been stood with little use for 2-3 weeks.
Can anyone suggest what the issue might be? The garage is going to clear the error codes soon and see what error codes come back after that.
I really hope someone can help with my late 2002 X308 XJR. After being stood for a couple of weeks I fired it up and soon noticed a quiet but audible ticking noise early in the rev range from the engine bay when the engine was under load. The car drove fine but soon restricted performance was shown. After pulling over and turning off, the car started back up OK with no restricted performance but the orange 'check engine' light stayed on.
The engine is slightly lumpy on idle, and the quiet ticking noise is still audible early in the rev range, but it drives perfectly smoothly/quietly/pulls strongly other than that.
The garage has pulled a lot of spurious fault codes out and are investigating. The plugs are apparently fine, and they have reseated each coil pack without noticing any difference at all so they do not suspect a coil pack.
There is no rattle at all from the timing chains, and my car is much later than the supposedly affected VIN's from Jag's bulletin...
The battery is testing fine for them too, I know that low batteries can cause a multitude of odd errors. I usually kep the car on a trickle charger but am conscious that it has been stood with little use for 2-3 weeks.
Can anyone suggest what the issue might be? The garage is going to clear the error codes soon and see what error codes come back after that.
Why are the fault codes 'spurious'?
'Reseating' coil packs isn't going to do anything. You say your garage did this? If a coil pack is faulty the fault code will tell you which coil pack to change.
Despite what you say, it's still all pointing to a low voltage on the battery. Charge it again or go on a proper long run and see if the restricted performance is still happening. If it is, check that the alternator is charging.
But the fault codes are not spurious, so after doing the above, read the codes again and pay attention to what they are telling you.
'Reseating' coil packs isn't going to do anything. You say your garage did this? If a coil pack is faulty the fault code will tell you which coil pack to change.
Despite what you say, it's still all pointing to a low voltage on the battery. Charge it again or go on a proper long run and see if the restricted performance is still happening. If it is, check that the alternator is charging.
But the fault codes are not spurious, so after doing the above, read the codes again and pay attention to what they are telling you.
SV8Predator said:
Why are the fault codes 'spurious'?
'Reseating' coil packs isn't going to do anything. You say your garage did this? If a coil pack is faulty the fault code will tell you which coil pack to change.
Despite what you say, it's still all pointing to a low voltage on the battery. Charge it again or go on a proper long run and see if the restricted performance is still happening. If it is, check that the alternator is charging.
But the fault codes are not spurious, so after doing the above, read the codes again and pay attention to what they are telling you.
Thanks both.'Reseating' coil packs isn't going to do anything. You say your garage did this? If a coil pack is faulty the fault code will tell you which coil pack to change.
Despite what you say, it's still all pointing to a low voltage on the battery. Charge it again or go on a proper long run and see if the restricted performance is still happening. If it is, check that the alternator is charging.
But the fault codes are not spurious, so after doing the above, read the codes again and pay attention to what they are telling you.
I must speak to the mechanic further, I am probably losing stuff in the translation. He tested each coil pack in turn and did not find any problem.
I am not sure how the new faint ticking noise from the engine bay could be related to battery, but I will charge the battery overnight with my ctek charger. Thanks for your help.
The X300 was known for cracking exhaust manifolds that made a spitting or ticking noise at idle but I've not heard about the X308 doing the same. In any case a cracked exhaust manifold or split exhaust gasket is unlikley to affect either performance or idle quality.
One cause of rough idle that needs urgent investigation on the V8 is a slipped exhaust timing chain. A one tooth slip on the ex cam sprocket is not enough for valves to contact pistons but it's plenty enough to give a rough idle.
Unless your car has had the third gen metal bodied secondary tensioners retro fitted at some time it will have left the factory with plastic bodied secondary tensioners. The second gen type on the 1999/2000 on cars maintain chain tension by means of a spring rather than a piston actuated by engine oil pressure and that means they can fail with no warning rattle on start up. I'd suggest the first thing to do is remove the cam covers and make sure both tensioners are keeping both exhaust chains tight and the cam timing is OK. You'll be able to check that without special tools - just make sure with a straight edge the flats on both camshafts on both banks are all sync with each other.
Other causes of a rough idle can be inlet vacuum leaks anywhere downstream of the throttle body, a blocked part throttle breather pipe, dirty throttle body butterfly valve or out of spec air flowmeter. If your engine oil is really filthy or your engine is down on compression and forcing a lot of a lot of oil mist into the induction system that can affect idle quality too.
It's just possible you may have a failing coil pack or spark plug that's OK under load but unable to fire under the much higher resistance of a very weak idle mixture - but diagnostics ought to show that or any other engine management problems up.
One cause of rough idle that needs urgent investigation on the V8 is a slipped exhaust timing chain. A one tooth slip on the ex cam sprocket is not enough for valves to contact pistons but it's plenty enough to give a rough idle.
Unless your car has had the third gen metal bodied secondary tensioners retro fitted at some time it will have left the factory with plastic bodied secondary tensioners. The second gen type on the 1999/2000 on cars maintain chain tension by means of a spring rather than a piston actuated by engine oil pressure and that means they can fail with no warning rattle on start up. I'd suggest the first thing to do is remove the cam covers and make sure both tensioners are keeping both exhaust chains tight and the cam timing is OK. You'll be able to check that without special tools - just make sure with a straight edge the flats on both camshafts on both banks are all sync with each other.
Other causes of a rough idle can be inlet vacuum leaks anywhere downstream of the throttle body, a blocked part throttle breather pipe, dirty throttle body butterfly valve or out of spec air flowmeter. If your engine oil is really filthy or your engine is down on compression and forcing a lot of a lot of oil mist into the induction system that can affect idle quality too.
It's just possible you may have a failing coil pack or spark plug that's OK under load but unable to fire under the much higher resistance of a very weak idle mixture - but diagnostics ought to show that or any other engine management problems up.
Thanks very much for your time. I read that another XJ had the rough idle/ticking caused by a crack in exhaust near the oxygen sensor, which confused the sensor at idle but was OK when under load. I'll post back what the problem/fix was (soon hopefully!)
Jaguar steve said:
The X300 was known for cracking exhaust manifolds that made a spitting or ticking noise at idle but I've not heard about the X308 doing the same. In any case a cracked exhaust manifold or split exhaust gasket is unlikley to affect either performance or idle quality.
One cause of rough idle that needs urgent investigation on the V8 is a slipped exhaust timing chain. A one tooth slip on the ex cam sprocket is not enough for valves to contact pistons but it's plenty enough to give a rough idle.
Unless your car has had the third gen metal bodied secondary tensioners retro fitted at some time it will have left the factory with plastic bodied secondary tensioners. The second gen type on the 1999/2000 on cars maintain chain tension by means of a spring rather than a piston actuated by engine oil pressure and that means they can fail with no warning rattle on start up. I'd suggest the first thing to do is remove the cam covers and make sure both tensioners are keeping both exhaust chains tight and the cam timing is OK. You'll be able to check that without special tools - just make sure with a straight edge the flats on both camshafts on both banks are all sync with each other.
Other causes of a rough idle can be inlet vacuum leaks anywhere downstream of the throttle body, a blocked part throttle breather pipe, dirty throttle body butterfly valve or out of spec air flowmeter. If your engine oil is really filthy or your engine is down on compression and forcing a lot of a lot of oil mist into the induction system that can affect idle quality too.
It's just possible you may have a failing coil pack or spark plug that's OK under load but unable to fire under the much higher resistance of a very weak idle mixture - but diagnostics ought to show that or any other engine management problems up.
One cause of rough idle that needs urgent investigation on the V8 is a slipped exhaust timing chain. A one tooth slip on the ex cam sprocket is not enough for valves to contact pistons but it's plenty enough to give a rough idle.
Unless your car has had the third gen metal bodied secondary tensioners retro fitted at some time it will have left the factory with plastic bodied secondary tensioners. The second gen type on the 1999/2000 on cars maintain chain tension by means of a spring rather than a piston actuated by engine oil pressure and that means they can fail with no warning rattle on start up. I'd suggest the first thing to do is remove the cam covers and make sure both tensioners are keeping both exhaust chains tight and the cam timing is OK. You'll be able to check that without special tools - just make sure with a straight edge the flats on both camshafts on both banks are all sync with each other.
Other causes of a rough idle can be inlet vacuum leaks anywhere downstream of the throttle body, a blocked part throttle breather pipe, dirty throttle body butterfly valve or out of spec air flowmeter. If your engine oil is really filthy or your engine is down on compression and forcing a lot of a lot of oil mist into the induction system that can affect idle quality too.
It's just possible you may have a failing coil pack or spark plug that's OK under load but unable to fire under the much higher resistance of a very weak idle mixture - but diagnostics ought to show that or any other engine management problems up.
Gassing Station | Jaguar | Top of Page | What's New | My Stuff