If the MAF wasn't sealing to the intake pipe as you say then you might have found your issue. There would probably have been massive unmetered air leaks there throwing everything out,

 

I really hope you're right. However I did not hear any vacuum leak, or had rough idle...we'll see soon.

 

Is the jubilee supposed to go over the air pipe? This picture is the as found condition, the jubilee is next to the Maf, not around the air pipe.

 

FPR definitely should regulate the pressure and react to vacuum, if you are unable to get it to 3 bar than it may be lacking fuel at high rpm
Before you drop money on that part make sure your gauge is doing its job, always you can borrow one from local garage

 

MAF is cleaned (electrical plug also with contact cleaner), I got cold feet to clean the TB due to these warning about not cleaning the TB with Molybdenum coatings. I have no idea if my throttle body was replaced and if it has this coating (by the car S/N it should be), but I can't see the famous sticker anywhere (pillar B or throttle body), so I prefer not to touch it just in case...

I attached the jubilee clip properly and all the rest. The fit looks tight. I was eager to see the results, as I have been reading from people with a similar issue (air intake improperly attached and stalling at high power demand).

Aaaand...car won't start. Everything lights up on the dash as normal (fuel pump as well) but when I crank it, no starter motor noise. After that, car won't let me turn the key to start again until I go back to position I one time.

Car won't lock with the fob, and headlights don't seem to work (position lights yes). Battery?

Battery is at 12.2V, not too high but the other day I measured the same voltage and had no issue to start.

Is it possible that I have damaged the MAF and now the car get no air flow input? But then why does the car does not lock? I guess it is the battery but, may I have damaged something or make a short circuit somewhere? When I connected the negative battery terminal (the only one I removed), I thought I see some bit of smoke coming out, but maybe it was just breathing condensation from low temperature.

Any suggestion? Thank you so much.

 

OK, false alarm. I tightened the battery clamps and car starts.

However, the issue is still there. It looks like it drives a bit better or a little bit less of shaking at 4000 rpm but I think it is just the placebo effect.

 

Does it shake with gearbox J-Gate in 2 or 3 ?

 

Yes, in all gears.

I have tightened the air pipe again in its seal against the MAF rubber, as it was a bit of a bended fit the first time.

I'm checking manifold absolute pressure as displayed by the OBD. 50 kPa at idle. Values go well above 100 KPa and even to 300 KPa at WOT sometimes. It does not look to make a lot of sense doesn't it?

Do NA cars have a MAP sensor, can it be off?

Next I'm cleaning the TPS contacts, but I'm losing hope of finding the issue myself. I really don't dare to do a pressure test while driving, which I think would answer all the questions.

After that I'll do a drive test tomorrow. Then I need to think the next steps. Injectors cleaning sound good and might try it anyway. I think a work colleague can lend me a pro diagnostic reader, but it won't be soon.

I also would like access to a lift and check the fuel lines for bending. After 13 years at rest, I'm starting to suspect the pump was replaced and maybe lines damaged in the way.

 

i don't think pro reader will show much more than one you have now
Have you looked at spark plugs condition and gaps?
if your gauge pipe is long enough you should be able to hang it with the strap on the driver side mirror and close the hood, then get on to some village road with little or zero traffic and test it there, 10 minutes job

 

Clean the throttle bore and plate: CRC makes a cleaner that is safe and effective. Use a soft dowel to hold the plate open, with a soft rag, clean out the crud. Make sure everything is air tight when you reconnect.

 

I just cleaned the TPS contacts, although access isn't the best.

I notice than when pushing the pedal to the max, my OBD returns a +/- 80% absolute throttle position. When I turn the accelerator cable reel with my hand, it can reach 100%. Don't know if this date is useful, honestly.

At least this proves the throttle body can open to the max?

 

It just seems odd I get absolutely no code with my OBD. Key on engine position 2 with MAF disconnected shows a CEL restricted performance on the dash, but the OBD does not show anything.

Spark plugs, not yet. Monday I'll call the mechanic who replaced them, are X308 finicky with the spark plug brand?

 

Throttle cable is not adjusted correctly, it must be in high 90-ties when pedal depressed, 80-ties is too low, you can have a look at this thread, fairly simple job
https://www.jaguarforums.com/forum/x...-03-xj8-72814/

Spark plug brand is up to your taste, some last longer others not as much, but electrode gaps are quite critical and by their color and deposits you can tell state of combustion, it is quite useful for diagnosis but if your plugs are new they may be still too clean to tell anything

 

The problem can also be stiff ball bearings in the throttle body. The throttle cable is not connected directly to the butterfly. With the pedal fully depressed the butterfly may not open 100% the grease in the bearings drys with age and causes resistance, my 1999 would only open 50%. I dismantled the throttle body and added new grease with a hypodermic needle attachment on my grease gun. Four bearings if memory serves

 

Can I check this visually? With air pipe removed, should I be able to see the plate moving right operating the cable by hand?

 

Yes, but I did that. One quarter turn resulted in the reel not pushing against the stop, and high idle!

 

Yes you can check the throttle body, remove the air pipe, then operate the accelerator cable to 100% and see what the butterfly plate does. In my case it was not opening fully

 

Cleaned the throttle plate with a dry cloth. Plate opens fully pulling the accelerator cable to max.

By the way, there is a humming noise from the throttle body motor, it has always been there, in case it is relevant.

My theory is that the 3.2 and 4.0 share the same throttle body, so in order to draw the necessary air, the 3.2 does not need to go close to 100% in throttle operation as the 4.0, does that make sense?

Does anybody know the air flow values of a 3.2 engine at WOT?

Otherwise, I'll report back when I get fuel pressure values, I'll make it happen one way or the other.

Thanks as always for you help.

 

I see your logic, the 3.2 won't need as much air as it's a smaller engine.

However I'd assume with the same throttle body, pedal components etc it should be set the same to get the full travel. If for no other reason than it's easier for the mechanics etc to work on them at the dealer. The different mapping within the ECU will then allow for the lower flow rate on the 3.2 when calculating the fuelling.

 

So we have throttle body which opens fully pulled by cable but not by pedal operation, you should track where it fails cause it is loose somewhere, it should open 100% regardless of the engine capacity
Humming is normal or at least common so don't worry about it
I would dig a bit more into fuel trims, you have posted the graphs but really it is hard to deduce what exactly was the numbers while misbehaving due to graph being too compressed in time line. Could you observe both long and short trims in the moment of engine shaking? do the number stay high/low for longer or they just spike but ecu corrects immediately?