well it feels like ecverything!

If someone can steer me in the right direction as to the fault with my Jag be most appreciated!!

Long Story short, Car has been of the road for 12 months but worked perfectly and was used regularly before this. I came to restart it and the battery was very weak, cranked but wouldnt fire, eventually got it going assuming it was maybe a little flooded. Battery is poor though and it needs to be jumped to get going BUT.... it runs very rough, especially at idle! Basically sounds like misfiring on cylinders 3 and 4. Try and accelerate and it sounds like a Harley Davidson on 3 cylinders and shakes/rocks the car from side to side!!

I started by changing the crank sensor along with two coil packs (cylinders 3 and 4) as these seemed to be the ones that made little/no difference to how the car ran when disconnected so assumed they were at fault, still the same. Ive tried disconnecting the coil packs one by one and they all change the running of the engine so I assume are all working, Ive also checked each for spark and all cylinders have one.

Called the RAC out who spent ages on it for me, good spark at every plug, fuel at the fuel rail and all injectors firing, good compression in all cylinders.

He did however find a stored code of P1621 - ECU Fault, had a quick glance at the ECU, disconnected it and reconnected it, seemed ok connections were clean, no immediate signs of corrosion?

Car is still running bad, anyone on here had a similar fault? any ideas on where to go next? Am I missing something simple??

Any help/ideas appreciated!

Cheers all!

 

Try this, disconnect the battery and give it a full charge. This will also give the car chance to reset itself.

When fully charged, reconnect and try again.

Make sure you have the radio code before you disconnect.

Check also the connectors to the MAF and engine control module.

 

What model year are we talking about?

 

Assuming HAHA, its a 6 cylinder "R".

How fresh is the fuel??????. After 12 months I reckon it is possibly no more explosive than water, and simply pouring some fresh in with the dregs will not cut it.

I would drain the tank, pour some fresh fuel in, replace the fuel filter, disconnect the fuel inlet at the rail, attach a hose out over the wing into a can, and flush that clean fuel thru, by switching the ignition ON and OFF numerous times, OR, bridging the relay socket points.

After that long sitting, the list can be very long, and some serious systematic diagnosis will be needed.

One of my V12's sat for 3 years, and fresh fuel, as described above, had it roar into life very easily.

As already said, a flat battery is a very big NO NO for these cars. Te alternator simply will not substitute for a charged battery. Charge that thing, FULLY, then see what happens.

 

Well, Grant:
Just a wild *** hunch here, BUT P1621 is a CAN bus error and is not applicable to the X-300 according to any literature I have.

Not to say any advice given so far is incorrect in any case!

 

Bugga.

We will wait fro a response.

Fresh JD just poured, so we will see.

 

Hey All

Thanks for all the replys!

Its a 1996 XJR6, Fuel is 12 months old but it was parked up with virtually an empty tank 0Miles range according to OBC, Ive put around 5 Gallon in along with some "dry fuel" additive to hopefully sort out any water/condensation in there aswell. Ive also now out a new battery on it so as to eliminate that as a possible cause.

I took out the ecu again and opened it up for any signs of damage but absolutely none.

Fires up fine as usual but still has a misfire!?! Just seems weird that it ran so well prior to be of road!

 

Twelve months isn't all that old for gasoline.....my experience is that it takes much longer than that for it to go stale....but you never can tell, as the saying goes. No doubt many variables come into play.

Water/condensation/contamination in the fuel will certainly cause a real problem, though.

If nothing else the fuel issue is a possibility that must be eliminated. I'd remove the fuel filter and cut it open.....or at least empty the contents into a clean jar. Some clues might well be revealed.

If the fuel issue leads nowhere then it's back to the drawing board. AJ16 engine misfires can be very frustrating.

Cheers
DD

 

my 95 xjr would started idling very ruff to the point the car would shake badly. to my surprise a new temp sensor fixed the problem. my 2 cents

 

Misfires fixes are all over the map with these cars.

My *most recent* bout with engine misfires was fixed by merely replacing spark plugs. HA! Who woulda thunk it. Such a simple fix concluding a rather tortuous journey.

But, faulty coils have truly been the bane of my existence with this car....with some of the agony self inflicted.

Cheers
DD

 

My 97 XJ6 had similar problems. After checking all the usual suspects, I bought a camshaft alignment tool and sure enough the camshafts were a few degrees off. Adjusted same now runs smooth as silk. Arch