XJR X308 coughing under hard acceleration

[Zippyworld]

Hello,

Does anyone know where to start with a coughing / blowing issue, the car not me ?

When I put my foot flat down or nearly flat down she’s really not happy, it feels like a misfire and blowing off through the exhaust, its the only way I can describe it.

At 5500 revs all is fine, its just under load. In all gears.

Could really do with some advice on this one please, any ideas ?

Thanks

[Zippyworld]

This is going one step further now, thecarhas shown a fault code P1601. Incorrect control module.

There have been no modules replaced or tampered with.

Anyone shed some light on this please ?

I am changing plugs and coilsas a matter of routine and elimination.

[flying-banana]

Speaking from an experience with my old S-type R, get the exhaust cats checked...
I had a problem that felt like the engine was pinking, really wasn't happy to accelerate under heavy load...
...fortunately the guy who used to look after my S-type had not long diagnosed a similar problem with an XKR so knew where to look

[jas xjr]

I had a problem similar to this but it was intermittent. Turned out to a fuel filter problem

[Zippyworld]

Thankyou for the input, fuel filter had been changed and made little difference. Cats are good too.
Its starting to look a lot like one of the fuel pumps.
There is a new fuel pump going on the car this week.

Will let you know the outcome.

[Jagaddict]

Sounds a bit like the back of the EGR may be loose?

[melhookv12]

XJR has 2 fuel pumps, one to start it and one to run on light load. The second comes in under load.
It uses the secondary pump to start it if that makes sense. 2 relays also.
www.jagrepair.com

[Zippyworld]

Finally got to the bottom of this.

Two things, the first was a knackered fuel pump.

The secondary issue was a real head scratcher, it turns out that the Lucas coils ( which I thought were OEM ) well one of them was faulty, despite being brand new.
It didn’t show up on the dash because it was only losing a spark at full throttle.

The final repair was replacing with used genuine coils from a breaker, too pricey from Jag.

The car had a used pulley replaced on both the waterpump and AC unit. It also got a new alternator and it still bloody squeals when started from cold.....!