I needed to bounce this off you please. When I got my 1998 XK8 8 months and 17,000 miles ago (it now has 60K miles), I could light up the rear tires by just stomping on the gas. It didn't take me long to see that if I turned off the traction control I could really smoke them.

Now I'm not a young guy showing off, but I'll admit that I am using this as an emperical measurement of power. I am no longer able to do this with anything less than a super sharp turn and the traction off. Even then it is brief. Where I am going with this is trying to figure out if something has caused a loss of power, it has me stumped.

Background, I put new Pirelli z zero's on within 10K of purchasing the car. I'm still using them, they certainly don't get stickier with age right? There are no codes stored, overall I am happy, but like 90% of you I want the car at 100% and am trying to figure this one out.

What should one check at 60K miles if they suspect a loss of power? Would a dirty fuel filter cause this without setting any codes? The only safe place I could do a zero to 60 time was on a strech of road that is either slightly downhill or slightly uphill - my choice. The uphill was 7.5 seconds at best; Downhill was 7.0 seconds. Everywhere one looks, there appears to be a different result for the zero to 60 times in the early XK8's anyway but I include this as one more data point.

Thanks for reading this, I'd love to hear what you think.

John

 

I meant to note that both the throttle position readout and visual inspection shows 100% throttle at both the pedal and the adjustment cable inside engine compartment.

 

Would it be correct to assume that you do not have a clogged air filter?

 

Wait, light the tires up by stomping on the gas? My 03 will not do that! Running Mich Pilots and these are some big, wide sticky tires. Off the line is not the XK8's strong suite I've been told so I assumed everything was OK. However.....if I should be able to do a burn out from a stop I want to be able to, not that I would but if something is not right with my car I want to fix it.

 

I've changed the air filter, thanks for asking. I should have mentioned it. I have never changed the fuel filter or the spark plugs. As an FYI, I've been using "SpeedView" a free andriod app to measure 0-60 times. It displays speed, distance, as well as 0-60 and (though I've never used it) 1/4 mile times. Apparently it relys on GPS for 0-60. You select the fact that you want to measure it. Once you stop the car, it knows you are at zero, and as soon as you go, it starts counting. Then once you hit 60mph it stops the clock. I wish it displayed a graph of the accelleration, but that probably comes with the upgraded ($$) version, not the free one. Well please keep you ideas / experience comming. thanks.

 

Jandreau, I should have acknowleged your email. 6 months ago if I stomped on the gas, the Pirelli P zero's would light up. Of course the Traction control jumps in to stop that right away, so turn it off and I could get smoke. Now it was 60 - 70 degrees cooler then, could that be the difference? I doubt it is ethanol fuel mixture related, so I'm just trying to figure it out. John

 

Not sure if it is as dramatic on the normally aspirated cars, but 60-70 degrees makes a very noticeable difference in XKR performance.

 

I believe the dual fuel pumps are XKR only but not sure about early years of XKs, There was a thread on this recently.. second kicks in at higher demand.. if you lost one it might be getting fuel starved and IF you put 60k miles on that's alot of fuel, filter prob needs a replacement.. good luck

 

I would tend to run a compression check and make sure that your not suffering from Nikasil cylinder liner erosion before you try any more burn outs.

 

Rperformance, that is a scary thought. I think I'll change the fuel filter and see what happens. Frankly I couldn't afford to do anything about the Nikasai issue if it happened, so I'll keep my fingers crossed.

On the topic of fuel filter replacement, I've noticed many of the threads dealing with that acknowledge the good old gas spray as pressure decreases. Guess it's time for me to ask: Why wouldn't one just pull the fuel pump fuse and idle the car until she stalls, then disconnect the fuel line. Always worked on my Ford Bronco, but then again our Jaguars have little in common with Broncos. Wouldn't that work? Anyone know where the fuse is?

Thanks, Joh