2003 XK8 coupe, 170k km... Hello all,

Engine started misfiring whilst running at idle, 2 days ago, and threw the amber check engine light yesterday, which is on all the time now. Spent a great couple of days reading all the threads about misfiring, fascinating stuff on fuel trims from fmhertz, coils, injectors, swapping out from left to right banks, spark plugs etc.

Initially thought it was caused by me nearly running out of fuel and therefore possibly getting residual gunk from the tank clogging through the fuel system, filter and injectors. Now think it is an air leak, since fuel consumption is twice the normal, which would be the ECU trying to mix extra fuel in with the extra oxygen I guess.

Anyway, when you quickly stab the throttle a short distance (2 cm) and just before the engine starts to rev-up, there is a distinct hissing sound like an aerosol spray for about 2 seconds, then it disappears. Air leak...

Sound like its coming from the intake manifold... any ideas for a solution guys and gals?

Simon

 

What codes do you have?, check the intake plastic tube for cracks.

 

I should get the code reader tomorrow and I've order a new air inlet pipe since this one's got cracks I've gaffer-taped over.

 

I use an UNLIT propane torch and judiciously move it in and around and along the intake tract. When the RPMs rise you found your leak.

 

Hissing with misfiring or uneven idle is almost always an air leak.

Ideally use OBD live data to check fuel trims. You want LTFTs within 5 of zero.

Even a tiny leak is bad and will cause trouble.

 

Update: I'll post some screenshots from torquepro..
Fuel trims, bank A above, bank B below.
Seem normal?

Codes showed cyl 2 misfire and excessive emissions only.. Nothing about running lean..

First code cyl 2 misfire. See other screen snap for possible causes. Then emissions too high code.
Possible causes from the DTC pdf
So what did i do given the above? Quick replacement of the cyl 2 spark plug.. And..
No change.. Still getting misfire..

Not yet received the new air inlet pipe, but not sure that's the problem, since the lean DTC did not show in the diagnostics.

Anyone else been down this road?
Otherwise I'll have an indy take the left cam cover off and check the gasket for leaks.

 

Swap the coil pack between #2 and the adjoining cylinder. See if the misfire moves. If it does replace the coil pack.

I'd still replace the intake pipe as you noted it has cracks. In-metered air is an issue.

 

P1316 is more serious - see the jag codes doc / workshop manual. You're doing cat damage.

If at idle LTFT2 is too large.

 

I swapped the coil pack per Jandreu's useful suggestion above, but it didn't make any difference, cyl 2 is still mis-firing.

 

So now it looks like the injector may be the problem. The LTFT2 is a bit high, but the ECU can compensate all the way to 25 area.

 

Probably not the injector. They rarely fail and also would not account for the hissing sound.

Rev and does the LTFT2 improve?

 

Sorry I'm away for 4 days so this is from memory. For further info, here is the vacuum reading at idle.
Readings at idle, warming up.
When revving to 2000 rpm, vacuum reading goes from - 22 in/Hg to about - 15.

Ps... Air inlet pipe wasn't delivered to me as programmed, yesterday before i left. So the tape is still on the bellows of the old one.

To answer your question from memory {not a good idea} i think ltft2 went to zero at same time as stft2 went higher.

I'l pprovide more useful info when I get back on Thursday.

Simon.

 

Can't see anything useful there, so still post #11.

 

JagV8 from Yorkshire (I'm from York) wrote:

>Rev and does the LTFT2 improve?

I replaced the air duct pipe with a new one. Followed your suggestion... when revving at constant 2000rpm, LTFT2 goes to ZERO. Is that good or bad? Signs that there is no air leak, since trims are balanced??

OBDII is still reporting misfire on cyl 2 and the hissing sound when you stab the injectors is still there - but this may just be the fuel injectors working?
Next I plan to replace the injector on cyl 2. I've already changed the plug and swapped the coil with another, so those causes are eliminated.

Having real problems to deal with is almost good, makes you forget about wanting to change the speakers in the front doors...haha

 

Dropping usually means an air leak, the reason being that at high air flow the leak hardly disturbs the expected fuel mix.

When only one side is high you're usually looking for something that affects only one bank (may be either side but normally the high one) so you can rule out items common to both.

Injectors tick rather than hiss in my experience and with 8 of them there's quite a rhythm.

Sometimes you can use a stethoscope (or not so good a screwdriver/piece of wood to conduct the sound) to get closer to the source of a noise. With care - moving parts...

With #2 still misfiring it's worth checking wiring & connectors (or swapping the plug if not yet done).

 

Just swapped coils for cyl 2 and 8, no change, 2 is still misfiring.
I've ordered a fuel injector and will replace it in cyl 2 when it arrives. A local shop here wanted 320 euros to clean the injectors, not much less than the replacement cost.

The VVT o-ring near cyl 2 is leaking oil - could that be letting in air and causing a misfire?

 

I seem to keep referring back to what I've just posted...

 

Usually when a VVT seal goes bad it's become hard as a rock and loses it's ability to seal. Yes it can allow unmetered air to get into the system but I don't see how it would create a consistent miss on just one cylinder.

I've read no mention of any of the P0171 or 74 codes that would indicate a lean condition. Rather a repeated misfire on #2 with the attendant O2 sensor warning of possible CAT damage. You've swapped coils with no change and as I recall you installed a new plug with no change. A faulty injector wouldn't cause a plug to misfire but would lead to a lean condition being seen by the O2's as plugs fire regardless of how much or little fuel is in the chamber.

Since it wasn't a coil problem and you're NOT getting any lean codes it would seem reasonable to look for the problem to be in that particular cylinders ignition wiring or problem in the ignition control module.

Also you're not getting, or haven't reported getting, a P300 RANDOM misfire code as well as a P302 so the #2 misfire isn't random but consistent leading even more to an singular ignition fault being the cause. Make sure the ignition wires leading to #2 haven't gotten pinched and shorted under a hold down screw at the coil & plug. (Don't ask me how I know this can happen)

 

Finally solved - thanks for all your suggestions everyone.
Caved in and took it to the dealer, it took them 2.5 hours to find and solve the problem - an ignition coil had failed (closed circuit, so no error code. There would have been an error code on the coil, should it have failed open circuit).

If you remember, OBDII reported misfire on cyl 2 and I had tried swapping the coil with another, hoping that the misfire would "move". That logic doesn't work immediately, since you have to go through several cycles before the code will come up on the newly-erroneous cylinder.

According to the CoC, the XK8 was built in September 2002, after a build specification dated May 2002. This caused a bit of confusion in identifying the cylinder with the problem. Jaguar WDS reported misfire on cyl 2, whereas topix (SDS) reported misfire on cyl 3. The actual cyl in error was left bank (bank B/bank 2), second cyl from the front. According to what I know, this is either cyl 2.2 in the old nomenclauture, or 4 in the new (post May-2002). To be sure, the garage pulled a working coil from another client's xk8 in order to settle the question.

Runs great now!
Also pleased to have learnt a little more, over the past couple of weeks. You appreciate the engineering that went into these beasts.

 

I've got a 2010 XKR crapped out on the highway, she got me home. Put my scanner on it, gave me a P0300 multi misfire. Drop it at the dealer got me nervous. Chked Rockauto for coil packs 27 to110 USD each. Quit a range. i.ll see what the dealer gets.