I have a 2004 XJR I have owned for a year now. When I first got it, I did a 0-60 run with my friend in the car (I am 195lb, he is 180lb) and we clocked 4.7 seconds. This weekend I was driving with a friend and we decided to try a few, as he wanted to see what the car could do. I tried with DSC off, DSC on, using the manual and just having the shifter in D and I couldn't do better then 5.8 seconds. I'm still 195lbs and he was lighter then the last guy, 160lb.

Some things to rule out:
It was not wet out, we are in southern GA so just above sea level, same road I did my first 0-60 run on. Tires are good, it was a cool night, premium fuel, cleaned MAF, nothing I can see blocking air flow, no check engine light, and engine was warmed up. The trans seems to shift fine.

The car drives just fine, and I take the best care of it I can. Its not super noticeable but it seems its lost some of its push me back in the seat power, which is why I bought it. Big good looking sedan that could shame most other cars who pull up next to me at a red light.

Any ideas?

 

My experiences with early XJR...not sure if/how much they'd apply to your car

- Supercharger belt slipping?

- Intercooler pump working? Mine failed...it *does* make a difference

- Air pockets in intercooler flow, or low coolant level in intercooler?


Cheers
DD

 

Its possible the super charger isn't giving full boost I guess. It should be 13.1 lbs boot if I'm not mistaken. How would I check this? I found a place with a Dyno so I could see if I'm getting the proper HP/Torque I should be getting to the wheels but even if it came up low that wouldn't tell me what the engines problem is.

 

How about the Air intake? Filter age, type, quality, etc? As the internal combustion engine is a massive air pump, it needs to breath! The exhaust system my not be clogged a bit and need some freshening up. When was the last time the complete fuel system was treated to clean out the debris and help even, consistent fuel injector spray? Pull a few plugs and check the dryness/dampness, gap, age etc? Was the fuel from the same source or a different brand (possibly less than the posted 93 octane). How about the engine oil? Using the same brand? Conventional? Synthetic? oil filter? Differential oil age, type, etc? A few years of higher mileage annual use can wear down the transmission fluid causing slower shifts and longer times getting through the gears. Transmission filter? Just a few thoughts I'd check out...

Respects,
Rags

 

With a boost gauge




Right


Cheers
DD

 

Nice! @ 4.7 even the new 2014 XJR is barely so slightly faster!
I hope you get to the bottom of your issue. One weird thing I notice on my XJR is that I sometimes get heck of a stronger pull if I ease the gas pedal down vs flooring it. I think the engine management doesn't like it.