Not a bad idea. I can take them off and clean them out for sure. I did just service them not too long ago flushed, back flushed, new baskets & O-rings.

 

I am wondering about the MAF as well. There are 3 things that control the fuelling: MAF, Coolant temp sender and the ECU itself. Might be worth trying a different MAF, just to see what happens. Similarly, ECU's are cheap on Ebay might be worth checking that too. Could be a bad solder join in the ECU, that isn't unheard of.

I have had both the MAF and ECU go bad on my XJR, but it was jump started and the PO connected the cables the wrong way around!

If you try unplugging the MAF, the ECU should go into a default mode and the car should be drivable, but rich if you're not at sea level. Worth a try to see if it's better, worse or the same? drive as you normally would on a road you know and have the trip computer on instant MPG and see if there is a difference with the MAF plugged in or not.

 

I'd still try another MAF
but also the fuel pump in the tank might be faulty (possibly affected by the additive), not working properly when high flow is demanded of it, but OK at idle.
I don't know how this would fit with the 72% opening throttle however

 

While it's possible a fuel pump could go bad, the more likely scenario are the coil packs in the end. The additive is just a concentrated version of what is in Chevron's fuel, let's all get over the idea I erroneously put out there that the Techron was the culprit.

I am toying with coil pack removal and eliminating a bad one. Anyone with a quick link as to how to diagnose the coil pack both on and off the car? I have a multi-meter...

 

Yet if it idles smoothly, it's probably not coils. Usually coils produce rough running, and you say this is smooth, but no power? Certainly not impossible to be coils, though.

 

Jagboi,
if you're not literally putting out fires (excuse my poor Canadian geography), then can you indulge me and try to figuratively put out this fire by trying another MAF?
if you like I can post you one, but it'll take a week from NZ.
I have a spare LHE1620AA, bought by mistake a year ago when I was after LNA1620AA for the XJR. Despite knowing the difference I clicked 'Buy Now' in a state of post-work stupor
It's yours if it might help.
(otherwise I'll keep it for my 3.2 someday)

 

The fires are in the northern part of the province, about 750 km from me. However, it's not my car we are talking about that has the problem! SD96XJ6L is the owner with the unhappy Jaguar.

 

Does the car roll freely? Could you drive it to the top of a hill and let it roll down to assess whether there is any dragging or binding in the brakes or drivetrain? I know you have dismissed the brakes already, but the engine might "suddenly" have had a lot more work to do, which would neatly explain all of your symptoms. If you were overfuelling to the point that power was disappearing, there would be some smoke and a strong smell of unburnt fuel, which you havent mentioned.
Is the 13-15 mpg figure a brim to brim calculation, or from the trip computer?

 

I don't believe it is a transmission issue, when you step on the gas it just doesn't go like it did. I swapped out some OEM coil packs and they MPG went down a bit. The MPG calculation I am going off of is the one on the dash computer. It's usually quite indicative of the "health" of my engine I find.

 

The reason that I asked about the source of the fuel consumption reading is that the high fuel consumption contradicts theories about poor fuel supply causing the power loss ( poor fuel supply would sap performance, but it wouldn't use a lot of fuel!) . The trip computer fuel consumption is based on a calculated fuel consumed figure ( number of injector firing commands X normal injector capacity) . I am wondering if in fact your fuel consumption reading is a red herring ......
I know you don't want to hear any more about additives, but what if it did what it said on the tin and loosened off some carbon or gum and it lodged in, say, the fuel pressure regulator? The fact it was replaced before you put the additive in is no protection from stray debris in the fuel supply.
The timing of your administering the additive and the sudden onset of the problem seems a remarkable coincidence.

 

This is a convincing argument for sure. I will disassemble these areas and clean out again. I did clean them out before I serviced them (injectors, FPR).

 

Yes, but you put the additive in after you serviced them...
Do you still have the old fuel pressure regulator? Might be worth putting it back on, in case the new one is faulty. A faulty regulator would scupper your fuel pressure in no time if it didn't start to close as the revs rise.

 

My fuel STFT & LTFT were good though...? What about my Air Fuel Ratio, any other diagnostics I can read and share the will shed some light on this?

 

The ratios would be OK, it is the absolute volume that would be the problem. That is to say the Right amount of air for the available fuel is getting in, you are just short of fuel as a result of poor fuel pressure. At least that is the hypothesis!

 

Hey, I'm willing to try and eliminate any variables and appreciate any and all input. What should my air/fuel ratio be?

 

Air to fuel ratio

15.0:1 is lean
14.7:1 is stoichiometric
13.0:1 is rich

 

I know this is a wild card, but is the parking brake stuck on? They are miniature drums machined into the rear rotors, so hard to see if they are on or not.

Thinking of the comments above, if the fuel trims are ok, that means the system is doing what the ECU is commanding, but that doesn't mean the ECU is commanding the right thing. A big driver is the coolant temp. As a trial, unplug the coolant temp sender wire, and short the connections on the plug with a straightened out paperclip or a small piece of wire. This will tell the ECU that it is fully hot and see if it drives any differently. You'll probably have to have the car warmed up, I doubt it would start otherwise. This test will eliminate the coolant temp sender as a suspect.

If it passes, then we need to look at MAF, ECU or O2 sensors as suspects. If all those check out ok, then it's something in the driveline that is sticking or binding causing drag.

I forget, do you have a code reader that gives a live data stream? Just wondering if you can check that way what coolant temp the ECU is reading.

 

The parking brake is definitely not stuck. I do have an OBD II scanner via Bluetooth I run Torqe App on. The coolant temp sensor as replaced with OEM as was the air intake sensor which was faulty, but didn't solve the underlying issue.

I will get updated data from Torque for the following, please add anything else of importance:

Air Meter
Air Fuel Mixture
STFT
LTFT

 

Some observations for your consideration:
1) In another thread (I think), you said your throttle only read 70 something % at WOT. Is that still the case? The TPS feedback is definitely worth checking.
2) You said the mechanic tested your MAF sensor. How? That is not an easy part to bench test. Notice the powerful suggestions you are getting from others on this issue!
3) I assume the fuel trims you reported are at idle. To really get information from fuel trims, you need a chart of them under varying conditions. It would be pretty difficult to get the crappy performance you have without some really screwed up fuel trim. I am not saying the A/F is the root cause, but it cannot be right given what you report. The fuel is going somewhere!
4) Does your exhaust stink?
5) It is probably time for a compression test.

 

Just a note from my experience with LSx motors: for an LSx, the TPS reading at WOT is 88%. It's not a bug, it's a feature.

So maybe just maybe, for a Jaguar, 70% may be WOT. But I'll be happy to be corrected if wrong.

In this case, does the OP have any logs of WOT before all these recent problems? If not, then ignore this issue for now.

Padre