Yes, I'm still not convinced it is the MAF sensor, I just figure it is a lot easier to anti-up for one than tearing the gas tank out and replacing the fuel pump and filter.

I'm hoping it IS the MAF sensor because I DON'T want it to be the fuel pump, so I figured I'd buy an OEM Denso made in Japan MAF sensor to be sure, and then figure things out from there. Plus I think that fuel pumps suffer "sudden death" rather than than a slow agonizing death?

Fingers crossed it is the MAF sensor....................I'll post the results!

p.s. are there any precautions to take when installing a new MAF? Should you disconnect the battery etc?

 

Disconnect the battery before disconnecting/connecting anything (except when changing the bulbs but even then, who knows).

 

Okay, will do, thank you.

 

Disconnecting the battery OR removing the ECM fuse will ensure that the 'learned' fuel trims are erased so the LTFT and STFT can begin with ZERO.

bob

 

OEM Denso MAF sensor arrived today (i'm more and more amazed at the shipping speeds!)

I disconnected the battery, installed the new MAF, the engine revved to about 4K for 5-10 seconds on start up, but soon settled down

I went for a test drive, and it ran fine, but of course it may take several days/weeks of driving to fully test that this was the problem.

Will report what happens.

p.s. for reference, the Jaguar part number for the OEM Denso MAF sensor is LNE 1620CB and is listed at $290.00. The Denso part number is DMA-0114 and is available from several sources for around $120.00


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Well, went for a 40 miles drive, stopped several times to let the car sit, everything was fine. Came home, let the car sit in the sun for 1/2 hour, started it up, everything was fine. Let it sit another hour, started it up and it ran like a dog, spluttering, banging, pinging, etc. So the MAF sensor was not the cure.

I hooked up my OBDII device, It gives me a lit orange triangle with the exclamation mark in it, but I don't know what that signifies?

The only "code" is a P1000......."System checks not complete since last memory check", and I'm not sure if I'm supposed to do anything about this?

I'm unsure where to go from here...................the car runs fine, and then obviously something breaks down, for some unknown reason, and the car will barely run.

Anyone got any suggestions?

Should I suspect the fuel pump?






.

 

Up to now the only code you have reported is P0174 system to lean bank 2.
You stated having misfire but didnt say any codes for this.
You say there is plenty of fuel pressure at the shrader valve at the time of rough engine running.
You state there is no air leaks....

But the only tdc you have points to a poss air leak.
Have you looked in pending codes. ?
Also i would be looking at the freeze frame data for the P0174 (to late if you cleared the code)
Also you need to look at the fuel trims.

Hope this helps,

 

Yes, the only code thrown has been the P0174
When the engine is running rough, it is REALLY running rough, barely running at all, lumpy, not enough power to move the vehicle, pinging, rattling etc.
Pressure at the fuel rail shrader valve.
Cannot see any air leaks, had the air intake tubing off twice to check for leaks. Nothing.
No pending codes
I have cleared codes from previous episode, plus I don't think I would know how to read the freeze frame.
Don't know what the fuel trims are.

After sitting in the garage for an hour and a half the car starts and runs fine!

And of course the problem will repeat when I put it through the same procedure. Something triggers the problem when the engine is hot, and then parked for a certain amount of time....10, 15, 30 minutes, and then goes away when the engine/vehicle cools down. I even started to think it was a fuel vapor lock problem, but not sure how to check that.

I can't for the life of me think what the hell to look at next.



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I would look at the fuel psi by connecting a fuel pressure gauge to the shrader valve.
Do a leak down test to see how long the psi takes to drop..
You may have a bad leaking injector (this could poss cause your symptoms)..

 

Thanks for that suggestion, I will try it.

When the trouble starts the engine is not running on 7 cylinders though, it is barely running at all, like there is something drastically wrong. And as I said, most of the time the car runs just fine, it's only under certain circumstances that it acts up.

But I will definitely try what you suggested. Thank you.

 

It appears to be heat-soak related. The engine will typically reach the peak temperature some 15-30 minutes after switch-off. The only thing I can think of, that is attached to the engine and affect all cylinders, is the crank position sensor. Although not electronic, it has very fine wire windings that may, at certain temperature (expansion) start losing continuity if the sensor is on the way out. Perhaps worth a try.

Otherwise, when I checked the price of a new MAF at Barratt, I found that, for LNE1620CB, you can buy only the sensor element. OEM (LNE1620CB#): https://www.sngbarratt.com/uk/#!/Eng...e-8ecff1b9e3f9, Aftermarket (LNE1620CB*): https://www.sngbarratt.com/uk/#!/Eng...5-78d74f5ae59f.

 

So I bought a fuel rail/pump pressure gauge set from Harbor Freight (excellent value BTW at $17.15) and hooked it up. With the car running perfectly the fuel rail pressure is right at 35psi.............which I think is normal?

I'm trying to duplicate the reoccurring problem so that I can test the pressure when the car is running like crap/barely running.

 

I think I read somewhere that it was 43 psi on the V8 , I can be wrong

 

Maybe a bad temperature sensor: sticking, thinks it is still colder out and is over enriching. But, pulling on straws.

 

With the engine not running the pressure on the rail is 44psi, when the engine is running it is at 35psi.

 

Where is the temperature sensor?

 

So I found this procedure.........
https://www.jaguarforums.com/forum/a...-pressures.pdf

With the engine running the fuel rail shows 36psi
With the engine running and the pressure vacuum hose disconnected and plugged, the fuel rail pressure shows 46psi
With the engine off the fuel rail pressure slowly rises from 36psi to 42psi

Of course, now that I have the rail pressure gauge hooked up I can't get the car to replicate the problem!

 

OKAY! So I finally got the car to replicate the problem, while the fuel rail pressure gauge was connected, and there is virtually zero fuel pressure when the problem occurs..........so I must assume that it must be a fuel pump problem (lucky me right!).

Any comments or agreement on this?

 

Might not be the pump, but the CIRCUIT.
Check the wires, Relay and harness connector to the EVAP FLANGE on the top of the tank.

Could be the short link harness (EVAP FLANGE to pump inside the tank) or overloaded connectors (BURNT?).

The link harness might be part of the sender itself with the tanks from VIN F20645? I forget all the part numbers.

Burnt relay contacts are common and a sign that the pump is failing OR the filter is CLOGGED.

bob

 

Thanks Bob,

I had already checked (and replaced) the pump relay, it looked fine, and as a new relay didn't seem to make any difference I replaced the original.

But I will remove the trunk lining and check as best I can the electrical at the tank.

I am unsure of the history of the fuel filter, so I must assume it is original, (17 years and 78,000 miles), although visually it looks very clean and bright and may have been replaced at some time.