I forgot to add that this is a 2001 XJ8

Okay, I've given up on finding out if the ZF can be replaced with the MB transmission, apparently I've asked for a purple unicorn. I can't be the first person to consider this, but I digress.

I connected my OBDii reader to the Naguar last evening and was greeted with 7 Faults.

To me, the first 6 may be traceable to one common source, and you guys know these 4.0 liters far better than I, so if you can make a connection I would certainly appreciate the help.

P0171 - Powertrain - System too Lean (Bank 1)
P0174 - Powertrain - System too Lean (Bank 2)
P0133 - Powertrain - O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P0153 - Powertrain - O2 Sensor Circuit Slow Response (Bank 2 Sensor 1)
P0332 - Powertrain - Knock Sensor 2 Circuit Low Input (Bank 2)
P0455 - Powertrain - Evaporative Emission Control System Leak Detected (gross leak)

There was also a P0733 - Powertrain Gear 3 Incorrect Ratio (which is no doubt due to the bad valve body in the ZF) as well as a P1000 which seemed to be a generic (could mean anything code).

My first reaction to all these codes is a fuel delivery problem, however the previous owner had a Walbro 255lph fuel pump installed.

I'm suspecting there may be a significant vacuum leak (primarily because the computer obviously thinks the gas cap is off), because when the car is cold it runs rich, and stumbles. It improves slightly as the engine comes up to normal temp, but it still has a rough idle.

I've checked the engine bay for potentially obvious vacuum leaks, but combined with the fuel pump replacement, I suspect there may be some bad connection to the fuel tank, like the vapor recovery line (if there is one?).

I also suspect that because of the "System too lean" codes, that maybe the replacement pump is junk or was not installed properly. I've watched a few videos on replacing the pump, and I think I would probably junk the car before fighting those fuel lines above the rear diff.

Any thoughts?

 

Did you just get the car? Did all these codes pop up at once ? Or after the fuel pump was replaced ? It does sound like some could be related to fuel pump replacement. You might need a knock sensor. That's not too bad of a job. You could have a leaky evap valve, not uncommon. Intake leaks are sometimes hard to find. You could clean the MAF and do a hard reset, maybe fill in with some more details. I know dropping the tank is not something to look forward to.

 

Yes, I've had the car only about a week. I traded a BMW engine and transmission for it.

Here's what I know about the car which has 125K miles.
At 83K miles, Jaguar replaced the engine under a recall or warranty issue (I'm not certain which) and I'm not sure if they replaced all the sensors, or just the mechanics.

At 113K Miles, the transmission was rebuilt (by a 3rd party), and the valve body wasn't replaced, for some inexplicable reason. It started acting up again after only 12,500 miles, so the 12K mile rebuild warranty was exhausted.

The person I traded with, replaced the fuel pump because the car wouldn't start when he bought it, he also replaced the MAF sensor, and drove the car for approximately 1500 miles, before the transmission started acting up, and he parked it out of fear of further damaging the transmission drums. While it was parked, he rebuilt the front suspension because he thought he was going to keep the car.

As for the codes all popping up at once, I'm unclear on that. My reader didn't show a date stamp on the codes, and it's quite possible that these fault codes are quite old. I reset all of the codes last night, and haven't driven the car, however I did start it after resetting the codes and it continued to idle rough, and I could smell that it was running rich.

I've driven the car only three times, for a total of about 100 miles. The transmission is exhibiting the flare shifting problem of a bad valve body, so when I drive it, I shift it manually and let off on the throttle just before shifting, so that it doesn't slam into the next gear.

Out of those 100 miles, I have randomly received the "Restricted Performance" message with the yellow light, and once received the "Transmission Fault" with a red light causing the "limp home mode" in the transmission. I'm assuming that is what tripped the P0733. Also, four different times, it flashed the "Check gas cap" light, and yes, I checked it.

That pretty much exhausts my knowledge about the car as it sits. It's still not as many codes as my 1997 BMW 540i 6-Speed had, but thankfully the Jag has fewer warning lights. It was hard to drive the 540 in the dark because the instrument cluster was lit up like a christmas tree. LOL

 

I think that you only have one major fault, the P0455, which is causing all the other codes.
I would suspect that when the pump was installed, they have dislodged part of the evaporative emission hardware or a pipe at the rear of the car, causing a major air leak.

 

Ignore trans codes for now - likely caused by engine ones as trans won't like engine misbehaving.

Look at fuel trims, hot engine, parked, at idle & about 2500 rpm. Do you see quite high positive that drop as you rev? If so you know for sure you have an air/vacuum leak. If not, you go looking for evap or O2 issues.

Don't drive it much till fixed as it's likely damaging the cats as it can't get fuel/air right.

 

I suspect this to be the case as well. I spent several hours Sunday in the engine bay going over every possible vacuum leak area. Short of an EGR gasket failure, which I couldn't get to to test, everything under the hood is tight and sealed.

Next weekend I'll work on pulling the tank. I would rather not drop the rear diff, or the entire rear suspension since I don't really have the facilities to do that.

 

To me, the trans codes are a known quantity. The ZF needs a rebuilt valve body.

I'll check with Torque on my tablet, but I can tell simply by the smell of the exhaust, it's not running right.

I think the cats are already shot, and replacement is not going to be cheap. The cats sound kind of hollow at certain RPMs, at certain load, and the car is louder than it should be.

Out of curiosity, does anyone know if the upstream O2 sensors are similar to the Subaru upstream sensors which are actually just Air/Fuel Ratio sensors used by the ECU to adjust fuel trims?

I ask, only because I had a very similar problem on an '01 Subaru Outback, and because the Upstream (pre cat) sensor was toast the ECU there kept sensing lean mixture and would bump into the max limit on fuel output.

It exhibited many of the same issues this car does.

 

If the upstream sensors are toast you should get P 1646 or 1647 codes.

 

I wasn't sure if the Jag ECU was capable of identifying the failed upstream sensors.

The Subaru wasn't, because the sensor was just an Air/Fuel ratio sensor, and didn't have a failure range in the ECU. When the upstream was bad, it played havoc with everything else. It kept sensing "Lean" and kept adjusting the fuel as rich as possible, without ever throwing a fault, until the downstream sensors threw a fault.

I'm going to look for other vacuum leaks, but I may tap the upstream sensors and monitor them directly to see if they're within range. That is if I can find out what the range is supposed to be.

 

I don't believe you can monitor the upstream sensors. They are wide band sensors and not voltage based, I believe they are current based. Someone else will chime in, and there is a lot in the archives. I asked this same question myself. You can get them reasonably priced though

 

If they're wide band, then they are almost identical to the Subaru Air/Fuel Ratio sensors, which are also ridiculously expensive.

This may go back to monitoring with Torque through the OBDii for the fuel trim measurements.

The slow degradation of drive-ability would point to failing sensors. Since it ran fine for about 1500 miles after the fuel pump replacement, but is slowly getting worse.

I'm not ruling out a serious vacuum leak, because of the Emissions "gross leak" fault code, but just to rule out bad sensors, I'll probably replace all four up and down stream sensors. The car had 125K, so replacing those sensors can't hurt. Now, I'll just have to take out a small mortgage to pay for them. LOL

 

With no P1646/7 code they're probably fine so I'd fix air leaks first.

 

You shouldn't have to pull the tank to check the evap system, most of the stuff is underneath; a box and some hoses.
If you do ever need to remove the tank, need a special tool to unlock the fuel hose connectors.

 

After removing all the carpet/trim in the trunk, and checking all of the evap recovery and vent hoses, finding only one that had a questionable clamp, I turned my attention back to the engine bay.

My first reaction is "What were they thinking?"

Seriously, making all of the vacuum hoses on the engine out of that hard plastic? What? Were they out of bendy straws?

I found four of the vacuum leaks by simply tugging on these brittle little tubes. And what is with those "o-ring sealed" connectors? How can that be that loose and possibly make a good vacuum seal?

I keep telling myself that I am essentially only $400 into this car and somewhere under the annoyances is a pretty good car.

Fixing the vacuum leaks, certainly helped with the engine. It now has a ore stable idle and is much smoother all the way around. However, it had little effect on the transmission problems.

Unfortunately this morning, it popped an ASC Not Available, and TRAC not available. Eventually it went away, but was later replaced by a restricted performance light.

I haven't pulled the code to see what this particular fault is. I was too busy with a seat motor, and self inflicted clear coat repair. Maybe tomorrow.

I did however change both upstream O2 sensors, which also may have helped with some of the poor running situation.

 

Low battery will cause the ASC Not Available and the TRAC Not Available. If my car has sat for a while they always popup.

 

So far, it goes away quickly, and my battery is about 3 months old. It had sat for a few days.

 

Hang in there and keep plugging at it. Dogged determination will win out in the end.

 

In the finest British tradition, stiff upper lip and all that...LOL

So far, it has been a learning experience if nothing else.

I'm estimating about $1800-$2000 in repairs to bring this car back to serviceable condition. Making it essentially a $2500 Luggzury Cruiser.

 

After finding and fixing four vacuum leaks. It made a significant difference except...

First thing in the morning (cold engine), it starts quickly, and the RPMs run up to about 1100rpm for a second or two and then slowly drop to 750-800 rpm as it should, but... it stumbles and misses and smells way too rich.

After the temp gets to normal, it smooths out, and idles normally.

I would describe the stumbling and missing a lot like a small block chevy with a big cam.

It doesn't die, but it really wants to, and throttle response is sluggish when it's cold, it'll rev quickly but there's a delay.

Apparently this problem is related to closed loop mode, and I'm wondering if maybe there isn't another vacuum leak that is only evident when the ECU is in closed loop.

I'm beginning to think that I need to just rip all those plastic vacuum lines out and replace them all with new rubber hoses.

 

If you've fixed something that can affect fuelling, do a hard reset (because you want to force it to relearn all the trims etc).

(Generally you don't have to do that but instead can wait what may be ages for it to relearn.)

Then follow drive cycle or be patient till you've in effect done that.

Then look at fuel trims - well, you can do this sooner if you like but be cautious about the data as it may still be learning.

Fuel trims will tell you if you've a leak.