The car was redesigned for 2003. Some of the obvious changes are the 4.2, 6 speed, better headlights, drive by wire and stiffer body. Inside that list, the new motor has a long list of technical changes (double row cam chains and metal tensioners for example). Multiple changes in the design of the 6 speed vs 5 speed (besides another gear). Better headlight technology. Drive by wire vs cable. Braces to stiffen the body? Bolts, clamps, wire gauge, etc, etc.

Is there a reasonably accurate number for the changes? I've seen 400, 600 and 900. What's actually on the list?

 

They changed the fuel pump. I have to say it would be nice if we could get a really accurate list of every change that was made from one year to the next. I doubt Jaguar kept a record of that though.

 

While its true that the 4.2 had the new style chain and tensioners, its not true that they were introduced on the 4.2. The last of the 4.0 cars (engines made after August 2001) had the exact same timing chains and tensioners. Similarly the 4.0 cars are drive by wire having a cable from the accelerator pedal to the throttle pedal position sensor at the throttle body, just like the 4.2 does. The 4.2 does has a more expensive fuel pump compared to the 4.0, that is certainly true.

 

Check jagrepair.com, there is a lengthy pdf describing these running changes for each major "revision".

 

Weren't the later 4.0 chains still single row? Tensioners were changed to metal. Isn't drive by wire an electronic connect (not physical cable)?

 

It's a physical cable from the accelerator but that connects to a pulley on a throttle position sensor which controls the actual throttle position. The cable does connect to the throttle body but it isn't actually connected to the butterfly valve that is purely electronically controlled.

 

they’re all single row, the cam sprocket only has one set of teeth for the primary chains.

the silent chains and tensioners came in 6/2001 just before 4.2 production started


aj27 is drive by wire unless throttle motor failure. then it’s fly by cable limited authority

aj26 is pretty much drive by cable but the throttle motor can override the driver if throttle is applied. restricted performance isn’t fuel cut it’s the throttle motor fighting against you

 

fmertz - thanks for the suggest. jagrepair.com has info on the MY1999 and MY2001 changes.
kuddlesworth - thanks for the info on the fuel pump. Jag did a "Jag Technical Guide (XJ and XK Series) w/ detailed "Model Updates" for 1999 and 2001 (see jagrepair.com).
anyone in here have a cc: for 2003? w/ "Model Updates"? I'd like to see how many changes were actually done
On jagrepair.com, hope members have made donations. I did. There's a lot of work there
drove my 2000 project car today. after 6 mos, many hours, dollars, a breakdown (the car, not me) and lost sleep, t's fun to drive.
throttle adjust will help I think. antenna disconnect was a great small project

 

This? 2003 MODEL YEAR XK SERVICE TRAINING TECHNICAL GUIDE

 

Thank you! I'm looking at a low mileage 2003 so this is super useful.
The older Technical Guides did have a separate section called "model year changes" which included drawings.
In the 2003 guide, preface mentions 880 new parts and notes the key element is the new engine/transmission.
New parts = design changes which of course can be anything from minor tweaks to major revisions. Presumably the majority are good

 

Hope I'm not hijacking this thread. I have a 4.0 litre engine with a manufacturing date after August 13, 2001. How confident should I be that I have the metal tensioners (I have conflicting information). I was told that they switched to the 2nd generation plastic tensioners after the August 13th date and the metal tensioners were installed starting with the 4.2 litre engine. Asking for obvious reasons.

Thanks.

 

The general understanding is that there is no reliable way to determine what tensioners you have unless you open the valve covers and look. Another way to put it is that failed tensioners are too big of a problem to trust to anything other than your own (or trusted) eyes.

 

does not matter. all engines made after that date are metal

when the 4.2 started production the aj27 changed over to the tsubaki chain as well

 

Any technical difference in chains for 4.0 and 4.2?
Per your previous answer, they're both single row.

 

original is a iwis single roller. the later version is a single row tsubaki morse style chain

has nothing to do with 4.0 and 4.2

 

I just read an older article about this issue and it was Quoted at OVER 900 changes were made for the 2003 XK8.

 

Where did you find the article?

 

Hi, it took me a while to return the result I was looking for because I didn't reference my original post.
But here is the link that will provide you with your requested info:

2003 Jaguar XK8 & XKR (motortrend.com)

So it was a Motor Trend article (They are well respected).

Here is an excerpt from that article:Where the "new" really comes in is underneath and inside with 900 or so part-number changes. The most significant of these are the two new engines, which made their debut in the new S-Types but have been specifically engineered for the XKs. The XK8 is powered by Jaguar's new AJ34 4.2-liter V8 with Variable Camshaft Phasing. Power is upped 14 bhp from the previous 4.0L to 294 bhp at 6000 rpm and 303 lb-ft of torque at 4100 rpm. The supercharged XKR also has the 4.2-liter V8, but with fixed cam phasing, stronger pistons and oil jet coiling on the piston crowns' undersides to handle the additional stress and heat. The belt-driven rotor-type Eaton supercharger ups the V8's potential to 390 bhp at 6100 rpm and 399 lb-ft of torque at 3500 rpm.

Both engines are mated to the new ZF 6HP26 six-speed automatic transmission. The new tranny weighs only 196 lb (a 12% or 27-lb weight savings over the previous five-speed) and is controlled by a Bosch "Mechatronic" control module and operated by a revised version of Jaguar's famous (or infamous, depending upon your preference) J-Gate gear selector. A Sport-mode button next to the shift lever raises the shift points, allowing for better use of the engine's power. The rigid two-door monocoque body has been made even stiffer through the use of high-strength steels in crucial locations. The XK's suspension was engineered to match and enhance the shell's characteristics. Up front are double, unequal-length wishbones, coil springs and telescopic shocks. The springs are mounted directly onto the body, and the wishbones are secured to a rigid, yet lightweight all-aluminum-alloy front crossbeam. At the rear, an unequal-length wishbone layout with the driveshafts acting as upper links, coil springs and independent telescopic shocks complete the setup. Dynamic stability control and traction control are standard on the XKs. The XKR also boasts Jaguar's Computer Active Technology Suspension (CATS) system. The electronic control system combines uprated springs and anti-roll bars for increased roll stiffness and adaptive shocks that are continuously adjusted to enhance ride control and comfort.

The XK's brakes are more than up to the task of halting the V8's forward motion. The XK8 features radially ventilated disc brakes at all four corners, sized 12.80 x 1.10 in. in the front and 12 x 0.79 in. at the rear. The supercharged version has the prerequisite larger discs to handle the increase in power. The fronts measure 13.98 x 1.26 in., the rears are 12.99 x 1.10 in. The XKR also boasts Brembo-made four-piston aluminum calipers that bear the distinctive Jaguar R Performance logo. All models have four-channel ABS and Emergency Brake Assist (EBA).

Hope this helps