I can't understand what's going on. Jag started to make backfires on hard press on the pedal, may be in the past there was no(or we was careful in driving).
I can obtain good acceleration near to previous(but may be less), when the fuel pressure is around 4atm! But lambdas gives 0v, other -0.8!!! MINUS ?!?! Will change lambdas again(I put Bosch before 2-3000km) One week ago on the diagnostic plug I see 1,7V on B bank, 2.5V on A bank. Added Liqui moly injector cleaner, returned stock fuel pressure regulator, after 50km two blocks are on 4V on diagnostic, and as I said - lambdas seems not working Vacuum lines attached to distributor, without vacuum,ignition at 8 degrees BTDC(may be it is too big, but no detonation) engine a bit nervous. Even when there was pb with valve seat, I have feeling, the car was with much more power and smooth engine. Can it be 16CU guilty?

 

Was the 8 degrees BTDC at idle? It should be 18 degrees at 3000 rpm when hot, vacuum disconnected and plugged. That's approximately 0 degrees at 750 RPM, but it should be set at 3000 rpm.

What is the condition of the fuel filter? Fuel starvation will cause lean running.

 

Yes, 3 weeks ago, ignition was at 0 degrees, I moved distributor more(pin is broken, and permits more than factory boundaries) and without load engine was responsive, but.... Last night I switched lambdas off. This morning there was no backfires, seems to accelerate well, no misfires but engine is exactly a bit nervous. Today will put at 18 degrees, I need assistance for this. I think lambdas are gone. There was black sparkplug 2 weeks ago, and I added wd40 in fuel rail - may be this killed the lambdas. Filter changed, fuel is clean, will check fuel pressure drop when step on pedal But this morning, at least, no backfires. Oil is Mobil1 FS x2 5w50, but I "feel" engine as it is on 5w30 oil After retarded ignition(around 0 on 750rpm without vacuum) there is bang too rarely on very fast opening. I must change spark plugs too - Denso are some garbage seems to me. Two of them definitely defected.

 

Fuel pressure checks can be tricky. I did check mine several times also with reving the engine and even driving around small roads around the house. All seemed normal but i was running super lean. Turned out the inlet fuel regulator was messing up the fuel pressure at higher power. Worth a try to override it for a test.

 

Sorry, missed to mention - this regulator(first one) was removed in the beginning. Will start again with new spark plugs, new lambdas, etc Can't believe Also missed to mention - original filters and boxes removed from me - and seems, air is more than with original filters. But this was done more than year ago, and there was no problem. Sure, I have more than one reason for the current situ. A bit off-topic: lambda gives lean or rich with a steep curve. If 5.3HE runs on lean, narrow lambda is not easiest way to stay on lean - ofcourse, it is possible to check for the moment where is stoichiometric(just to calibrate), approximate the fuel needed for a lean and go there for a while, and loop again - but it is not working only on lean - engine oscilates - rich, lean..lean, rich, lean..lean, rich...... Wide band lambda can be used to stay at desired AFR without oscillations, but our sensors are narrow band.
P.S. I have feeling, all these things started after one drive of the car with forgotten cap of the coolant. around 7 liters coolant missed, but driver said, temperature started to rise But no loss of the power. And after that, it seems all was ok. Problems started later.

 

Today spark plugs changed with Champion RS9YC (OE011). Almost all the removed spark plugs was black, except 5A,6A - dark brown, and 4B - brown, 5B,6B wet. It means, 3.7atm fuel is too much and injectors are not equal. Decreased fuel pressure to 2.7atm, also base of the EFI decreased to 1 click from full left(as I understand, full left is lean, full right is rich). Steep press of the pedal leads to 2.4atm fuel pressure, which means, there is drop really. Capstan potentiometer shows 0.27V, when pedal is not pressed, when I put mechanically a bit forward to 0.32V, no change in the work of the engine. A bank not working as calm as B bank on low rpms, but on 1200, 1500, 2000, 2500rpm engine is working calm. Before to put injector cleaner in the fuel it was contrary - A bank was calm, B - not so calm on low RPM Will see with new lambdas, for the moment, lambdas are OFF Very steep press on pedal continues to produce sometimes BANG We must test 0-100km/h time, to be sure - is it lower power really, or it it feeling.

 

2.7atm sounds more resonable. When reving the engine the pressure should go up, not drop. (to keep the differential pressure between manifold and fuel constant)

 

If this is a 5.3 HE engine, then the fuel pressure should be at 2.5 BAR = 35 psi.

 

Original pressure regulator disconnected from me, and connected regulator, which can be adjusted, with manometer. But this regulator have no vacuum line. Will connect with original regulator in parallel, to see what's going on with the pressure, and if all is OK - will stay with the original regulator. And will remove catalytic converters.

 

Yes, I will return original regulator. But the car was very pleasant with this one, on pressure even less than 2.5 was with very good acceleration.

 

Fuel pump changed, fuel filter changed, original regulator returned. When I start engine, fuel pressure is 2.5 atm, after some seconds it drops to 2.2-2.3atm, on pedal hard press it drops for the moment at 2, then rises to 2.7-2.5atm and drops again to 2.4-2.3, depends on RPM(and vacuum). Bangs are the same, even easier I'm not sure, manometer is precise - it is from adjustable fuel regulator. So, next are injectors - two banks have at least one cylinder not firing on low rpm. Also will remove the catalytic converters - will put pipes On the exhaust pipes, near to collector there are some spirals from sheet metal - I suppose , idea is to stop ceramics from the crumbling catalytic converters to go in the cylinder(as Renault Vel Satis do it). When remove converters, is there need of these spirals, or engine is more powerful without them?

 

when checking the injectors, also check the fuel line from behind to the engine bay for free flow. If it is compressed or blocked somewhere and the flow is restricted the fuel pressure can drop under load.

 

Injectors cleaned, fuel line also. There was few small pieces in the fuel line. I am in doubts, they can decrease fuel pressure, but now Jag is THE BEAST again! Thank You all, for the good suggestions! A lot of the work was unnecessary, sure, but it is worth Will not remove catalytic converters, my son don't want it too. And it seems converters works, because on emission check, they told me - there is no difference compared to a new car on low and a bit increased RPM. Thanks to all of You again!

 

Forgot to post this strange spark plug: Part is clear white porcelain, other part is black soot. Spark plug is new, and colors are formed before the full power returned

black & white spark plug

 

I would say its too rich. Can you post a picture of the plug after a few hundred miles when its running good now? I am just interested what a "proper" running H.E. Plug looks like.

 

The plugs will look much like any other engine, a light tan colour.

I had a 1992 V12 and I did remove the catalytic converters due to physical damage. I didn't notice any performance or fuel economy increase, and the exhaust smelled more. I would leave them in place if they are working and undamaged. I think they were well designed and provide virtually no restriction to exhaust flow.

 

Yesterday after 177km passed with 62liters of fuel(35l/100km or 6.72mpg), I'v put 16CU EFI to "open loop". There is one wire near to diagnostic plug, and I connected it to chassis(as I understand, it is the way). As a result, 56km was passed with 6.6l - 12/100, or 19.6mpg. Engine was a bit strange on open loop - up to some position, there is no big power, very calm engine. From some point(may be full power switch goes on), engine becomes Jaguar V12 In fact, is was something like 2 barrel carbs - up to some point You have support and not big acceleration, and after that - power. It was pleasant, and I will stay on that, my son like it too(car is for him. EFI tuning pot is at one position before full clockwise, lambdas defected, it is for sure. Will get new lambdas, but I will not switch them on. Added coarse filter before fuel pump - old pump was full with rust bottom, fuel filter too. Have no courage to put second (aviation fine)filter after original one, I'm afraid from fuel starvation. Now 1B and 1A spark plugs seems to be normal.

 

Now I cut the filter, it is clogged. May be less than 1000km. For the resurrected car, this filter should be changed on 250-300, it seems