Hi all.


We've recently acquired a 2000 XJ8 auto 3.2 with 120K miles on the clock. Its appears to be in really good condition... with one slight niggle and I hope someone may have experienced something similar and can advise.


When accelerating hard with sport mode engaged the car reached 4500 revs, and then can't rev any higher, it feels as if the engine is being starved of either fuel or air ( mpg seems low e.g. 13mpg on mixed urban run) .


If I let off the accelerator , and then back on the car will engage the next gear up (3rd to 4th).


Another clue / red herring is that when starting the car it NEVER starts on 1st turn - but the 2nd!


We were advised that it might be a lambda sensor ( Bank 1 Upstream ) so we duly got this replaced but the car still isn't right. We've got a 1000 charity road trip coming up and it would be really good if we could get this fixed.


I've checked the plastic air pipe for splits and I did find 1 and that's been repaired and its had no impact.


Hopefully I've given enough of a description of the issue that one of you may be able to provide an alternative diagnosis...


Thanks

 

Do you have any OBDII codes set now? Obviously you did to identify the O2 sensor and intake vacuum leak.

Sounds like starving for fuel. Changed the fuel filter?

 

ditto: get the codes read. Also, clean the throttle bore and plate (carefully); clean the MAF sensor; double check for air leaks in the tube from the air box to the throttle; change the air filter, as well as the fuel filter.

Next up: plugs and fuel pump

 

I have the same symptoms, but have no check engine light thus no codes to access. Cleaned MAF sensor,cleaned throttle body, changed air filter, new plugs,fuel filter, checked for leaks in the intake hose. My car is also a 2000 xj8

 

I don't think there was a thread on this forum, but one of the forum members from the UK had similar problems on his 3.2.
It turned out to be the knock sensors.
No code, but broken enough to not only retard the ignition and starve the engine from power, but also upset the gearbox in higher gears.
​​​​​​He changed both sensors, and was terribly happy with re-found power and a perfect shifting box.

 

If a knock sensor is bad it posts a code the ecu then fully retards the engine and limits to 3000rpm, also a restricted performance alert in the instrument pack. More likely a dying fuel pump or it's link lead (if no codes or engine lights) - a trans issue or unmetered air leak if it's using lots of fuel. How does it behave out of sports mode?
Pull codes with OBDII reader.
Look at fuel trims short term and long term. posts your findings here.

 

That is about exactly what I mentioned to the owner, but it did not happen this way on his car.
We also saw the engine restriction, and the gearbox shifting as 2 individual problems, which to our surprise were related.
If I remember well, he had a coolant leak before, and the valley incl. the knock sensors were flooded.
I also think he got a code for a sensor at some point, but not in the beginning.

I don't say this is the solution, but I mentioned it cause the original poster's description sounds awfully identical, and not many will think about it.

Your suggestion of looking at fuel trims is a good start anyway, it will tell a lot of what is happening at those higher revs.

PS to 2jags1garage
I can PM you the owners details, very friendly chap in north-east of the UK.
I am sure he will be more then willing to share things with you.

 

https://www.jaguarforums.com/forum/x...00-rpm-174847/ my problem was a bad fuel filter. look at my old thread lots of good posts on it.