Engine hesitation when under load...

I own a 2001 xjr.  The car hesitates or seems to bog down when under load.  Driving the car conservatively around town is ok... but as soon as I step on it... it seems to pause... "lost" around 3000-4000rpm (through every gear)... for 4-10 secs... then seems to find itself... and go. It has been getting worse in the last several months.  I have had the vehicle in for service several times but no success.

Things I have had done:

Fuel filter changed
Fuel system/pressure check
New spark plugs
MAF checked and cleaned
No codes.

If anyone has any advice to this issue... kindly respond. Any info would be greatly appreciated.

SMX

The "check engine" light came on today :(

 
Hey there SMX and  to the forum. Sorry to hear about your problems and unfortunatley I can't help.
However, mayeb Jose or Nti  or one of the resident Jagtechs can help. Hopefully someone will be along soon with soem answers for you.
 
Jim

Hey bud, sorry I can't be of help either, but how about we move this to the XJR section and lets see if someone there can help you!

Let me jutst make sure, you've had your oil changed regullary right, ur not running oil that you changed like 8,000 miles ago are you, and youu've been using premium right? Just want to make sure, cuz it sounds like you have like a corroded engine or something, I can't think of the right word right now. 
 
Unless it's something obvious like the two things I just stated, I'd advice just taking it in for a diagnostic test at a dealer of jag service place

Pull the codes and let's start there.

are you sure you checked and confirmed  fuel pressure ,you might be running rich... you'll probably have rich running codes.. the vacuum line for pressure regulator, can  kink even more when heated up.. check the vacuum line for brittleness..whats your fuel trim?

Car going into shop again tomorrow. This is the first time the check engine light has come on since I've owned the car.
 
Will post codes as soon as I get a call from the tech.
 
 

quote:

ORIGINAL: 93xj6

Let me jutst make sure, you've had your oil changed regullary right, ur not running oil that you changed like 8,000 miles ago are you, and youu've been using premium right? Just want to make sure, cuz it sounds like you have like a corroded engine or something, I can't think of the right word right now. 

Unless it's something obvious like the two things I just stated, I'd advice just taking it in for a diagnostic test at a dealer of jag service place

Yes the oil has been changed regularly. 3 times in 12 months with premium oil. The issue has existed for a year or so... with the condition getting worse. Dealer was unable to determine issue on past two visits and not very helpful. Basically had said... sorry no codes... and everything checks out good. And said wait til something breaks... a hard fault. The mechanic I am dealing with now is under 10mins from my house. Really good mechanic... but I wouldn't say an expert on jaguars. He has access to code definitions and tsbs. As well as a mechanic friend who works at the dealer. But he hasn't been able to find the issue yet. But maybe the codes will point somewhere. I will post them tomorrow.
 
 

I agree with Jag_Genius about fuel pressure.  Have the shop check your fuel PSI under load.  My car would hesitate/delay shift/not have "oomph" under accelleration (like on the interstate on-ramp, passing, etc).  The "restricted performance" warning started coming on.  Took it to the Jag dealer.  My PSI was a couple pounds low under heavy accelleration.  They suggested a fuel filter change and injector service.  I also did a throttle body service for good measure.  BINGO!  No more issue .

Now, lots of pep.  Shifts like it should under hard accelleration.  You can actually feel the supercharger surging as you accellerate.  Ummm... what's the word....  oh, yeah...  exhilerating!

Codes:

P1603 EEPROM Malfunction

This is the only code which showed up. The code was cleared... and I have been driving it for a day. The hesitation issue still exists. No luck in finding out what it is...
 
The results of a fuel pressure check was 44psi. Does that sound right? And the fuel filter was also changed.

It is obvious there is a problem some where... but how come no codes?

44 psi is a little high.. does the fuel pressure move when WOT?  does it change?

Has the tech checked the function of the mass air flow meter?  My Jag dealer found that mine was malfunctioning adding to my hesitation problems under accelleration.  My issues were multi-fold.  Part of my lean and rich problem (depending upon throttle position and whether you where looking at bank 1 or 2) was reduced fuel psi - about 2 psi too low (apparently overdue filter change), malfunctioning mass air flow meter, and possibly dirty injectors and/or sticking throttle valve.  In addition to the new mass air flow meter, the tech suggested a "fuel service" which included the throttle valve and injector cleaning.  Your issue may have more than one cause.  Since you have already replaced the fuel filter, I would suggest the throttle valve and injector cleaning next.  It certainly can't hurt and it may improve your situation.  I would also look into the mass air flow meter.  If it's on the fritz, that may be part of your problem, as well.  Obvious question - you have checked your air filter and filter housing for blockages (very dirty filter or a wayward critter, or two? - hey, it happens!) 

We seem to see a lot more throttle body issues than air flow meter issue.  Remove the throttle body from the car and give a through cleaning.

Update:
 
I was gone on a short vacation. The car still has the problem. The tech was unable to diagnose the issue.
 
I think it's time for the dealer. I called them and described the problem... again. They said that if there are no codes they can't really help me. That the computer in the jag is smart enough to shoot codes for ANY issue. He said he can start troubleshooting... but possibly hand me the car back after 4-5 hours of labour and a bill... but the car not fixed. I said it can't be very complicated. It should be easy for them to rule out any systems which aren't the problem. After a bit of talking... he said his shop manager will go for a ride with me. No charge and no appointment. Supposedly he is very knowledgable on jags. That maybe he could suggest what root to take. So that will be next week.

I took my XJR to a "Jaguar specialist" who had the "diagnostic computer" but they werent able to pinpoint my problem.  I took it to the Jaguar dealer and they nailed it right away.  Of course, the total bill was $1,000 in addition to the stuff covered under warranty, but that's because I figured since the car was already in the shop, I'd get new brakes and front rotors and a few other little odds and ends.  It still runs great!    Give the dealer a shot at running a diagnostic.  It shouldnt cost that much and who knows - between the ride with the tech and the diagnostic, they'll hopefully find your problem

Good luck!    -Kent 

I think XJRs have 2 fuel pumps in the tank, right?  Unless you check the pressure (44 psi sounds a bit too high) under the load, you may not be able to check the pressure under the "actual" running condition.  If rich or lean condition exists, I think the computer should have already told you so by popping up some codes.  Well, the computer is not the most sensitive thing in the world though.

Good luck.

get someoen to check out your A/F ratios....... call speed shops. they can usually do it for a fair price if they have the right equipement.

FL XJR, im also from gainesville but tampa is my other location...what year n color is yours? i def dont see many running around up here...a white and silver 04 and newer and a handfull of 03s or older

Anthracite metallic (nearly black) with dark tint.  I have also seen a silver XJR around, as well.

-Kent

The problem has been resolved. It was a fuel tube which had a slit/kink in it. REALLY hard to find. It had to be removed to actually see the issue. It was replaced with a new one... car runs like new. What a relief :)

SMX,

Hey, that's very good news!  By the way, where was that slit/kink along the fuel line?  Was that under the hood?  Near differential area?  Or in the fuel tank?  Just for my curiosity...

Good to know you got your problem fixed, but could you give us a slightly more detailed answer.

It was a fuel line under the hood...
 
One end connected to a part close to the window side of the engine...behind supercharger. And the other to a part which is just behind the fan near the front of the car. It was a 1.5 to 2ft line.
 
I will get the exact names of the parts which the fuel like connects to/from once I talk to the mechanic.  
 
  

Thank you mate.  Sounds interesting.  Hope this proves to be helpful for future problems and let us know how much your gas mileage improves.