I have 3 Jags - 2 XJ8's and an XK8. A real niggle that I have is that the XK is so much more 'unresponsive' than my same year & same engine XJ! In the XK I can waggle the throttle pedal up and down 1/2" or so whilst cruising and there is no response from the engine, but on my XJ I only have to move it 1/8" and it's off like a rocket!

I drive both regularly, often one after the other to keep the batteries up, and it's so frustrating that the heavier car performs so much better than the little XK. For info, they are both 4.0L Nikasil engined (but built after Sulphur was removed from our petrol), and one is 3 weeks older than the other. Both have mileages about 70k.

I have adjusted the throttle cables so there's no slack, and I have swapped the MAF's over between them (even though they have different numbers). I'm wondering if it's a difference in either the PPS or TPS in the throttle bodies, or perhaps the EPROM mapping in the ECU? I'm tempted to swap the ECU's (or the EPROMS) over. Any ideas guys?

 

Don't swap any modules, let alone "EPROMS", without knowing 100% you won't immobilise the car - I think you may well get anti-theft and towing to the dealer to reprogram.

Look at the exact year diagrams for each car to see which PCM they use as they may well be very different and that would explain what's really going on. It would for an S-Type and one of your cars. Not that you put the year(s) anyway...

 

Yes sorry JagV8 - at the time I started the thread I han't found how to add a signature - now done. Both cars are 4.0L V8's from yr 2000, both about 70k mileage, and both built within a few weeks of each other.