Really rough running on idle

[Davidqhog]

Morning All,

The Daimler SV8 hasn't been used for 2 weeks. Under cover so not getting wet.

Took the cover off today, started okay then serious hunting and revs between 600 and 400 at idle. Assumed damp or something so gave it a good run. After 8 miles, pulled into a friend's drive and hunting again.

Another longer run at up to 65 mph. But weird noise as though the SC kicking in up hills.

Still idling rough, whole car shaking as though not firing on all cylinders. Stalled a few times too. On moving off from rest, throttle doesn't seem to have any effect until suddenly picking up, coughing a lot, several flat spots then almost normal above 35 mph.

I know an O2 sensor is duff but I don't think that's the issue as it has been duff for a couple of months now. I'll check codes tomorrow.

Anyway, any first thoughts from the team?

TIA.

DQ

[Davidqhog]

So pulled the codes today.

P0300 random/multipke misfire detected
P0302
P0303
P0304
P0305
P0306
P0307
P0308

Basicall;y only cylinder 1 not misfiring!

Also P1316

Not looking good!

[ptjs1]

Seven misfiring cylinders? I'd start by looking at the fuel system.

Is the fuel pump running correctly? Has it suddenly got noisier than usual? When was the fuel filter last changed?

Paul

[Davidqhog]

Paul,

Good point. I have had the car for 6 or 7 years, though 5 of those in storage. To my knowledge, the filter(s) havent been changed.

Don't think the main pump is making any noise and the auxiliary gets drowned out by th S/C when in use (not that it gets pushed that much with fuel the price it is)!

I'll try and get it to my local garage to check & replace the filters.

Many thanks.

DQ

[Davidqhog]

Morning all,

Turns out it was the air plenum/snorkel between the air box and throttle body.

One of the two dead-end tubes had broken off at some time in previous ownership, been repaired with glue and insulating tape and the mend had broken, so the ECU had no idea of how much air was getting to the throttle, hence the bad running.

It's a Daimler Super V8, essentially a refined LWB XJR, same engine, same S/C but the air snorkel fittings at the throttle body are slightly different and the bolt holes don't line up! AutoReserve Jaguar are looking to see if they have a match now we've sent back the XJR one they supplied.

In the meantime, fibreglass tape and glue will be used to hold it all together again!

DQ

[Davidqhog]

AutoReserve Jaguar came up trumps! They found a matching air snorkel somewhere in their warehouse and sent it over.

Cleaned it up and fitted and the engine now runs perfectly.

I now have a spare (the original) air snorkel as I repaired the broken joint! But I'll stick with the complete one.

DQ

[Andy P]

Well done David,glad you got it sorted out.
Take care.
Andy

[Davidqhog]

Cheers, Andy!

Really good to drive it again.

Now the X350 is playing up! Might be battery but ABS/DSC fault and a few other warnings that may suggest battery.

Regards,

DQ