Good you mentioned the units, that clarifies something.

My first thought is the MAF sensor.
Presuming this is at idle (~650rpm), that reading (1.3 lb/min = 9.8 g/sec) is almost twice the reading it should be.
Maybe not the only problem, but surely not good.

When I had problems with running rich, I found there is some fixed relation between MAF error and rich-error, and this could very well be the reason, or contribute at least.

Try disconnect the MAF sensor altogether and see what happens.
There should be a change.

My problem was as simple as the connector itself, I bent the pins slightly, rechecked the wire, and it never re-occurred.

With those mixture rates, I should not drive any more, you risk further damage.

 

So I disconnected the MAF, and it didn't make a whole lot of difference in how the engine sounded and felt. It started and idled a little rougher but not much. But it did change some of the readings. The AFR was moving up to 13.5:1 and even went to 18:1 at idle for a few moments. STFT moved up to -5% and at one point was up to 10%+. LTFT moved up to -8% and would probably move higher if I let it idle longer.

 

Well, to me that confirms your MAF sensor has a problem.

If you disconnect it, readings should get a bit worse, as the ECU goes into a less efficient default fuel map due to the lack of input.
Your case, the readings improve.

If I was you, check the wiring and the connectors carefully, if that does not bring improvement, I guess it is time for a new MAF sensor.

I was about to buy one from Rockauto, cheapest I could find that time.

 

I agree with Don B, from my experience when I have checked MAF readings, its usually been in gm/s, usually around 6-7 at idle.






Your STFT's are way out, anything over 5% is going to be a problem, specially that far. . Cleaning the MAF is always a good attempt, but doesn't always work, sometimes have to replace them. AFR is going to be related as well, which is indicating a very rich fueling condition.

 

I am thinking the same thing, I thought disconnecting it would have made a more noticeable difference. I'll get one and see what happens.

As I was sitting in it, reading the gauges and enjoying the comfortable seat, it occurred to me I have never ridden in or driven ANY Jaguar other than this one. I sure hope it's all worth the hassle!!

 

I just saw ericjansen's response, I agree..... I think you need to check that MAF, I've seen them do funny things to engines in the past.

 

I promise you it is!
It brings me an ear-to-ear smile, it almost hurts, every time I take her out .

 

Previous owner had installed a used tranny, and couldn't get the car to run right. You've seen all I did to try and get it going but nothing helped, including the new MAFS I installed this afternoon. Frustrated, I was messing around in the engine bay, tidying things up and looking for inspiration. After the tranny install, the owner hadn't done a good job of reinstalling all the wiring in the original positions, to the original mounting locations, so wires were everywhere. As you know, there are four O2 sensors, and the wiring was a tangled mess. It sure would be easy to get those wires swapped around. Guess what? Bank A top sensor was connected to the plug for Bank B top, and vice versa. I swapped them around, cranked her up, and all is good! Took her on a 20 mile test drive and no issues! LTFT is up to 11.7%, AFR is 14.6:1,and I believe MAFS got up to over 6 lb/min at WOT. And the only code is the P1000 which will probably clear with driving.

Thanks again to everyone for all the great support! Lesson learned.

 

Now that's good news finally! Do a hard reset to get the STFT's and LTFT's back to square one and start enjoying it.

 

I will do that tomorrow!

 

Bravo ~ Now start smiling if you don't already do ...

 

Yahtzee! You should be golden now. Look at it this way, you've learned a lot about an XJ 308 by taking everything apart and doing all those tests, so if you ever have an issue later on, you know what to look for. I'd get you a little black book like I've got, and keep as notes, never know when you might need them.


Enjoy the Flagship of Jaguar, the XJ!

 

OMG.

You want LTFTs near zero but give it a chance and see where it goes.

 

My main purpose in buying this car was to learn about Jags, so I feel like I've gotten my money's worth already! I plan to put some mileage on it this weekend and make a new to-do list.

 

David,

Congratulations! Your persistence has paid off!

I had forgotten the transmission swap, but don't know if I would have thought of the O2 sensors having been incorrectly reconnected. It's a well-known issue, though, and can require an "ECM reorientation" at the dealer. It's terrific that you were able to figure it out!

Keep up the good work and please keep us informed. I'm not far away so I'd love to see your car one of these days.

Cheers,

Don

 

Took another 20 mile drive this evening, and it ran really well. All the parameters were closer to normal, AFR about 14.6:1, LTFT down to 8%. I plan a longer drive this weekend and a little highway driving since I haven't done that yet. And I'll get it emission tested Saturday if it's still running right.

Don, I'm sure we'll bump into each other at some point, since we're almost in the same area of Nashville.

 

Those LTFT's are a bit on the high side, a full healthy 4L should run within some -3 till +3 depending driving conditions.
I however also notice short trips do fool up the numbers, and a real long and hot trip let those numbers stabilize.

Once you got things passed and things have cleared out, you might want to spend some time checking for vacuum leaks, rather common, surely if the car lacked some care.

And on a side note, you seemed to have read the forums well, so if you plan to keep the car, do a careful check on the coolant system: expansion tank cap, thermostat and thermostat tower, (valley) hoses, cross over pipe and hose clamps.
Your car will be thankful.