I'm gonna guess and say the shuddering is coming from either the Transfer case or Propeller shaft/Center support bearing..I've heard similar descriptions for these common problems

 

Its kind of the feeling you get when you stop and your front disc is bad...only its not happening when I press the brakes, just when I let of and then press the accelerator, and the wheels arent shaking, but its that type of drivetrain vibration. It does not seem fuel related at all. It seems to mainly happen in the 20/40 speed range

 

There are plenty of prop shaft posts, and I did have it looked at and my mechanic found it to be fine. The transfer case can cause that too?...like its on its way out, or does it need a mount?

 

I'm not a 100% on the TC case either Mark..but one way to find out, is to disconnect the Prop shaft from the rear differential (yes you'll have to remove the whole assy), Then see if the shaking is still there as you know it (you will have front wheel drive only)..if it don't shake or shudder anymore as you say, then we have an issue with the TC case or Prop Shaft..If the Shaking/shuddering is still there, then It's transmission related or it could be the flex disc between the engine and transmission.

 

Mark, I would probably put my money on the fuel pump as others here have suggested. It seems to me that if it's that directly related to the amount of fuel in the tank, that would be the first thing to check. I've never had to do that myself and it sounds like a difficult task unfortunately, but there is allegedly some way to cut an access hole through the body underneath the back seat. Maybe someone who has done that before can walk you through it.

The O2 sensors would throw a CEL, and this car seems to be very sensitive to doing so. I had a CEL that turned out to be an O2 sensor. I had it read by my mechanic who suggested I floor it on the highway in an attempt to clean the sensor. I did that and the light has been off ever since, and that was almost 4 months ago. My MPG wasn't noticeably different either, which leads me to believe anything even mildly problematic with the O2 sensors would be giving you a code.

 

Thanks everyon for the replies. The only reason I am doubting the fuel pump is because the car will "act up" at different levels , for example works great full, then gets poor when its 1/4 down and then great again when its 1/2 down. I do really hope I do not have a major problem here.

 

Two things comes to mind related to the fuel system...Fuel pressure regulator on the fuel injector rail and the Gasoline Vapor canister for recirculating the gasoline vapors...I don't remember if the X had either of these and I don't have my JTIS anymore for reference...

 

Thanks for all the replies to this topic. Because the car was not running at all due to an unrelated electrical problem that took several weeks to properly sort, I had not had time to pursue this problem.

First, the problem with the car "vibrating" was the prop-shaft bearing. The initial diagnosis of it being "fine" was wrong.

But the slight "heaviness" that is specially noticeable in stop and go traffic is still very much there, as always comes and goes.

Even though I have no codes stored, I am going to "throw" a few parts at the car to see what happens since no mechanic has been able to diagnose the problem

This is what I am thinking of replacing;

1-4 O2 sensors-because of what has been suggested on this thread
2-New MAF sensor-because mine might be faulty
3-Coolant temperature sensor for the fuel injectors since they always cause problems in Jaguars from my experience.

From then I will move on to fuel pump(s) and transmission solenoids.

The reason I am resorting to just "throwing" parts is because a) I am frustrated and b) because I get conflicting reports of how sensitive the car is to throwing a CEL. I have searched the archives and some say that the car will quickly throw a CEL for marginal O2's or MAF, while others say that it won't.

 

Just a thought...
The Jaguar X-Type isn't a fast car. My daughter in college has a comparable Mercury Sable. Same engine just 2 wheel drive. It's a monster compared with my X Type.
My 2.5 auto gets average around 20 mpg. But I do around 50% freeway driving.

 

Do you have it in sport mode? I keep my in sport mode at all times. I tried it with out it and it shifted like a granny-mobile. My only other recommendation would be to get a K&N air filter, change out the differential and transfer case fluids. I would also recommend high performance oil or an oil stabilizer additive, and engine treatments like Sea Foam have always worked wonders for me on other cars.

 

@Zach.Wheaton,
That's good advice right there bro!

 

I think they only put the 3.0 in the duratec powered sables, not the 2.5, so it would have more hp than your 2.5 X-type anyway.

 

One last thing on the Heavy feeling at take offs....Try the Sport mode J-gate gear change....compare and see if the automatic mode is taking off at too high of gear.

 

Your strategy of throwing parts are your car is likely to be very expensive.

I have read this whole thread and cannot see any diagnostics included anywhere. There was a suggestion early on that you check fuel pressure at the rail. A very good start point given your symptoms. Has that been done? What was the result?

If you don't have the equipment or the knowledge to carry out true diagnostics then I would suggest your money may be better spent finding a true diagnostic specialist (not a "mechanic" - no disrespect to mechanics).

If you are willing to do your own then all of the items you are planning to replace can be tested for the most part with specialist diagnostics. For the cost of a single O2 sensor you can buy a cheap USB Oscilloscope and measure the fluctuating signal from the O2 sensors and confirm whether they are working or not. Same for MAF. You should get a good view of O2 sensor efficiency by looking at STFT on your Live data from your OBDII scanner (it should fluctuate Rich/Lean by a few percent both ways).

 

I agree it's neither cheap or smart to throw parts, but neither the Jaguar dealership nor my Jaguar mechanic (he services my E , XJS and has been doing Jaguars since before I was born--) can find a problem.

Some of the items I want to change are of no consequence like the CTS and fuel temp sensor they are very cheap. Other items I am just guessing on based on past experiences. I know too well that just because an item tests good, it does not mean that it actually is, heat or cold or repeated operation can cause different results than when being tested. I had a shutting down problem with my XJS for six months, the throttle position sensor was tested2 times and came up as good, car kept on dying until I changed the said TPS on a hunch.....the car never died again. Point is I am reaching that point with the X type .

I plugged my obd2 reader and posted what I found here:

https://www.jaguarforums.com/forum/s...ad.php?t=97861

Any thoughts?

Thanks

 

Hey there, just saw your post on this and see you're at the stage of perhaps "throwing parts" at it, obviously frustrated by this.

Unsure as to what your mileage is now?
According to Jaguar the 02 sensors chould be changed in the 30k - 60k range

Had issues on my sons Vauxhall Astra at around 50k miles iirc and 02 sensors resolved the issue of hesitation / lurching and extremely poor mpg.

Depending on your current mileage it may be that your at that stage where replacing these will only benefit your ownership, especially if you're going to have it for some time.

As others have stated though, if you have the time / know how these can be removed and tested.

If you do have to replace any parts, depending on any specialist local deals available, remember to check out our vendors Jagbits, Rockauto etc as they offer forum discount and it may save you some $$$

Good luck and hope to hear how you get on with this.

 

I'll chime in with this: Have you checked operating temperature of engine, even if the gauge shows normal, How long does it take to get there, if your running cold for 1/2 the trip and back that will account for poor mileage.Below operating temp. (in open loop)the system is getting information from a standard (not adjusted) system (it leaves the 02 sensors OUT of the calculation) like carburetored engine with the choke closed. When the engine reaches operating temp it goes into closed loop NOW using the four 02 sensors to adjust fuel/air ratio to 14.7:1. So the quicker it gets to operating temp. and IF the 02 sensors are operating properly you get optimum MPG.Use your scan tool and see the operating temp(that the engine management sees) is 195 to 210 degrees F and it shows if it's in close loop(CL) or not, look at the voltage of the 02 sensors and if they oscillate like they should between .8 and 1 volt. As far as the shudder goes it COULD be a mount somewhere (motor, trany, exhaust.

 

uh-oh!

 

I must say that I am with JimC64 on this one - the O2 sensors.

Swap 'em all out. Fairly cheap and easy, and it may be the down-and-dirty quick-and-easy fix.

Don't use the aftermarket O2 sensors, either - go for the OEM "real" Jaguar parts. I keep hearing various "horror stories" about aftermarket sensors, most all cars. They just don't seem to be up to the same close specifications that the "real" parts need be.

The info they provide the ECU is absolutely vital for all-round performance, and they need to perform flawlessly from well below zero degrees all the way to red/orange hot temps, too.

 

Thanks for the information. I will be posting a video of what my OBD2 scanner read while driving the car. It shoes the oxygen sensors values as the car stood and goes. It should be helpful to my problem. I will upload it as soon as I can