Hi all,
I have just registered to the forum & have just purchased a 1990 XJS V12 Le Mans edition, the car has covered 66,500 miles & has full service history, the engine temperature, oil pressure is all fine & drives smooth but it struggles to pick up when the accelerator is suddenly dipped in fact in picks up better when steadily pressed.

The car hasn't been on a good run for months before i bought it & was told by the garage, that has maintained the car over the years that it needed a good clear out to solve the problem this was on the day of purchase where they checked the emissions & hooked in up to a diagnostics machine.

On the way home (all motorway) the car cruised perfectly at 70/80mph & after 30mins of driving I slowed down & kicked down the accelerator hoping for a better response after a few backfires it started to pick up but got to a certain point & backfired again where I eased off & steadily got home.

when I arrived home, temperature & oil pressure was all perfect, can anyone give me any pointers to what might be needed to correct this please?

I am in no way whatsoever a mechanic & wont be attempting a repair but would like to know what I might be in for when taking it to the garage.
Cheers Clarky

 

No idea where Hornchurch is, so the market specs of the car are a tad muddy, but here goes, boots and all.

It's a Marelli car, so the rotor and distributor cap comes high on the list.

The backfiring could be anything. If the rotor is arcing, as they do, one bank will be loosing spark, and when it returns, the unburnt fuel ignites.

It could be the "igniters" for the coils, of which there are 2, and thus loosing LT voltage, which is a sure fire backfire creator.

I would look for an Independent Jaguar workshop,a s apposed to any old mechanic, but that will depend on where you live of course.

 

+1 on having the ignition checked as Grant mentioned.

Lack of fuel can also cause a popping or backfire in the intake tract. Easiest place to start is the fuel filter. Have the shop remove the filter and empty the contents of the old filter into a clean jar. What the fuel sample looks like can be an important clue

Cheers
DD

 

+1, also not sure if the car has a kickdown switch but if so, check that too.

Assume it's Hornchurch in England, so UK spec?

Cheers,

Allan

 

Cheers for the info, yes Hornchurch, Essex England
Clarky

 

check your ignition and check your fuel pressure, I had similar symptoms with mine when I was having problems with the tank clogging

 

Thanks for the info
Clarky