Hi All

I would appreciate any help/pointers or advice on this problem which started 18 months or so ago, but the car has been parked up since then due to other maintenance issues (rust protection etc), but note the problem started before being left unused.

Engine starts and idles ok.
From cold or war/hot you can press the accelerator or manually operate the throttle on the side of the throttle body and half the time it noticeably bogs down, sometimes nears a stall.
It actually drives a short distance (1 mile or so) without any issues, but seems down on power.
We have also now noticed that just as you open the throttle there is a sound of air rushing through the intake manifold before it actually revs. That seems new, never noticed it before ever.
Since deciding to re-commission the car, we have done the following (note again problem started before addressing these):

• Oil and filter change.
• New NGK iridium plugs.
• New E5 fuel - Esso 99.
• New air filter.
• Cleaned MAF with a quality MAF cleaner.
• Cleaned MAF connections with an electrical cleaner,
• Checked the main intake duct and the smaller breather for leaks (does not seem to be any holes/splits visible).
• Double check/top up coolant.

Other things:
Checked Butterfly is opening when expected, and seems ok.
Yet to check the fuel filter but I do not see how that could cause this.
The fuel pump is running, although very quiet, possibly the original.
Fuel pressure at the rail seems low. Pressing the valve we only get it to squirt vertically about 2-3 inches which seems maybe low?
Not cleaned the throttle body yet. I see the way Gus cleaned his here JagRepair.com - Jaguar Repair Information Resource
or is it best with a manual clean also to get to the underside of the butterfly?

Any thoughts?
The new noise of air intake through the manifold seems quite odd and key to the problem.
Thanks in advance.
James

 

Have you changed the fuel filter?

 

Hi, no that is my next move. I suspect fuel delivery is an issue, so after that, the pump is on the list.
Not sure what is causing the noise though.
Thanks

 

A simple yet effective way to test for leaks at intake or manifold or air mass sensor is as follows: start the car; while idling, spray carb cleaner, lightly at any point of a connection or a gasket, choosing one spot at a time and waiting before spraying again. If you spray an area and the idle increases, there is more than likely an air leak in that spot. Spraying the cleaner, will introduced alcohol into the air flow and thereby increasing the idle briefly, confirming an air leak.

 

I was thinking of doing that also, I have seen guys with a gentle release from a butane torch moving it around the intake junctions and checking for the same.

 

OK, new Bosch fuel filter installed. The problem remains, no change.
Moving to the pump now, but the fuel pressure from a visible observation at the shrader valve is no different than our XJ8 Probably not the pump either then.

 

Now done that too. Released butane all around the inlet manifold and nothing, no change.

 

Now also swapped out entire throttle body with one off of my old XJ8 4.0.
Problem persists.

What else can this be?
Any ideas?

 

Also swapped the MAF, no change again.

Starting to feel lost now.

 

Can you take an audio clip of the noise and post up here?

Any codes thrown?

 

Hi
I hope this one works. The intake noise is not as loud on this, but you can hear it. If you rev gently the engine behaves. If you suddenly rev it (not WOT just a little) the revs dip quite a lot.

No codes at all which is a shame.
Thanks

 

I read on this forum of cars having air leaks in the intake tube. There seems to be leaks in the "accordian" section of the tube. Perhaps the information from the MAF is causing the ECU to send in to rich of a mixture caused by the air leak in the intake tube?

 

There seems be no splits etc under the flexi area of the tube.

 

The fuel pressure regulator also now changed from an old one. Hard to tell if it made any difference, effectively still the same.
It has been suggested elsewhere that one of the VVTs may be slow/sticky.

 

I hear the injectors ticking, then the dip when you press the throttle, but the noise when the motor catches sounds to me more like a chain thrashing or similar. Maybe that's just the acoustics on my laptop and I can't be certain.

Are you sure the noise is coming from the intake? Can you pin it down further:- back/front & top/bottom of the engine?

Does it sound happy if you hold at, say, 2000 or so rpm? Bear in mind the rpm limiter kicks in at around 3000 and causes the engine to run roughly.


Anyone?

 

What do you mean by chain thrashing? The chain against the tensioners/guides? The chains, tensioners, and guides were all changed to the latest type 4 years ago. Since then it has done less than 10K miles.
It is hard to hear any air intake noise on that recording, but it seems to be coming from the top of the engine around the inlet manifold. It is like it gasps for a split second before revs.
The VVTs sound and feel noisy (more on one side) when under a sudden/abrupt rev as if it has not engaged in time.
Also, holding the throttle open at say 2K, it is fine, nothing strange until you do another abrupt rev higher (not much higher), then it does the same and gasps and drops revs a split second.

Luckily all the parts we have substituted on this we have had as spares from my old XJ8, but we do not have any VVT solenoids. It may be worth taking them out for a clean, but there is a chance we know somebody that has a couple to borrow.

Failing this, kinda stuck as to what is causing the problem.

Thanks for your replies and assistance.

 

OK, it does sound a little different through headphones, but I can't definitely say what it is, and I don't want to lead you down a rabbit hole. Are you inside the garage or in the open air?

I wouldn't expect to hear anything from the VVTs doing their job, though.

 

Recorded in the open air.

You can definitely hear the VVTs, and touching the top of the plug you can feel them too. More one side than the other when the throttle suddenly opens. Gradually increase the revs they are quiet, which from what i read is fairly normal.

 

Quick update.
Following TSB 303-47.
Page 6 and starting P17.

Pressure should be 38 PSI + or - 5.
Fuel pressure is 35 PSI at idle, on a sudden rev (as per when the symptom occurs) it rises and peaks at maybe 40, then drops right back down above 30-32 then back to 35 after.
I think that eliminates the fuel pump and line.

 

Is the car showing anywarning lights or messages? Have you check for OBD codes and used a reader that can read Jaguar codes? I am surprised you are not getting any warning messages or OBD codes.