You most likely have a vacuum leak.

 

I want to clear up a few misunderstanding here. The octane is measured in RON in EU and as AKI in USA. AKI is average between RON and MON which are spread by 10 points(in US). Thus 87 Regular really has 87+5=92RON and 87-5=82MON properties.

In EU, the gasoline spec is only specified for RON characteristic, thus the Jaguar X-Type was designed for the widely available 93RON gasoline. 98RON and 91RON are also available in that region.

Given that people will used whatever is available and the car must be functional(ie., can not cause failure onto itself) for all available gasoline the X-type was designed to be functional at 91RON. US calibration was modified for driveability and homologation issues but the extreme condition calibration is carry over.

If you are hearing what seems like pinging(pre-detonation) the car program should back off spark and fuel map to compensate. If it does not there is something else wrong such as the knock sensor failure(do you have leaking coolant by chance?). Typically the spark and fuel map is most aggressively lean around part throttle condition as that's where fuel economy gains are had. At start and high load the spark and fuel map runs rich thus little chance of pinging.

 

Well I posted the problem and finally got a fix, hard to believe, but it works. The PVC hose was collapsing creating a lean condition. There is a new hose that is ribbed which elminates the problem. Fixed andwho would have thought.

I was getting my 2002 X type 2.5 repaired at the dealership when I spotted a 1989 XJS V12 that was near perfect. 114,000 miles, but recently restored. Never wrecked alway garaged and in beautiful condition. It followed me home, what can I say. Just drove it 350 miles and it runs great, real quick at emptying the 24 gallon gas tank. Replace the oil pressure sensor, fog light bulbs, fix the cruse control, the passenger side seat mouse (still under warrenty) and replace the under bonnet blanket and it is good as new.

 

Speaking of misconceptions, there is no fixed 10 point spread between RON and MON ratings of gasoline in the US or anywhere. The two are independently variable which is a fundamental reason that the AKI rating system was developed.

 

Ive always heard the octane rating was alot like oil weights. There isnt that much difference in one or the other for the most part unless you are talking super high horsepower. i run 87 octane in my 05 with no problem. is there any truth to this or not

 

None. Please go smack who ever told you that.

 

that would be due to the cheap gas....did you miss the sign on the gas cover that says premium unleaded fuel only?

it means what it says....good luck to you.