I have a xj6 sport 4 L on the 1996 N plate,this is my first jaguar.It has been off the road until I had time to get her running,for the mot it was the usual things brakes, lights exhaust leak and emissions ( HCs and lambda).Fixed the leak but this did not sort the emissions,so cleaned the plugs and done a coil test as I suspected a bad coil.(test was done by unplugging one coil at a time to see if the revs dropped)Cylinder 3 was found to be failing so changed the coil and put redex through the engine.The engine runs rough on idle but not like a miss fire the whole car rolls side to side revs at 800 to 900 but revs up nice,after 5 to 10 min she cuts out and wont start again until I give her some revs but I need to hold the peddle down or it will stall.So in brief runs lumpy at idle and dies as soon as it heats up also had a p1621 code.
I have cleaned and gapped the plugs looked at the coils cleaned the throttle body my OBD reader shows live readings from air temp ,air mass, throttle position and a very fluctuating cam sensor.
Sorry its a bit of a read but im kind off stuck and would love to see her running,thanks Andy

 

What's "redex"?? Did this show up after said "redex"?

 

Well P1621 is ECM immobilization input circuit malfunction according to the diagnostic manual. Not sure this has anything to do with your issue or not though unless there is a common electrical wiring issue to both of them?

You've checked the spark side of things, have you checked fuel pressure? You may have low pressure. Also what are your fuel trim readings on your scanner? Is the engine running lean or rich?

 

And by the way, don't bother with Redex any more... Get yourself some Forte (preferably 2 bottles considering the size of engine and fuel tank in Jag), you'll most likely have to order it through eBay, unless you have a mate in trade sector

 

Thanks for the reply's, Redex is a additive you add to the fuel to clean the injectors etc I used it to help with the emission failure,Yes JT it got worse after I added this but I don't think it was the cause.
Alan yes but only by disconnecting each coil at at a time and seeing the results and the engine does change on all 6,fuel pressure,don't have a gauge and my reader is not showing the details off the fuel trim but all plugs are black and a little sooty which may indicate running rich ?The code has been associated with lumpy running but with no real answer how to repair.

I have read lots of the threads here and else where and it could be a host of the sensors ,where is the information to test them eg ohms values ?
Is my jaguar the x300 model because I cant find a Haynes for my year ?
All the posts I have read don't seem to come to a conclusion so I will add my progress as it happens .

Thanks Andy

 

Yes, your car will fall into the X300 category,( 95-97 ) for which there is no Haynes manual available. Only for it's predecessor, the XJ40. However you can download the manual here on the forum, from the stickies.

 

jaguar xj6 rough running - YouTube
A video of the engine trying to run from cold,also changed the Crank sensor as I read somewhere here that it could be the issue sad face no joy.
pic of the old crank sensor.

 

The only thing I put in my tank is Shell V-power premium...period. Any other such "snake-oil" can interfere with 02 sensors, pressure regulators, pumps, filters and injectors. Sorry not a fan of fix-it in a can.

 

Yes I tend to agree this time its a product I have used many times before but I think this problem has been brewing for a few weeks now .

 

I would just do a major tune up?

Replace all coils n plugs
Valve cover gasket. Spark Tube seals
Cam cover grommets.
Oil n filter
Tranny gasket filter and fluid
Final drive fluid.
Coolant flush


See if those help maybe there dew for.repair anyways.


When I did that my rough idle went almost completely away

 

Yes I have got the plugs on way from Ebay only £16 that has been recommended here.Next I replace the coils and so on ,as with everything she was so close to being on the road im impatient lol

 

where did u get urs and how much did u pay?

your old one looks like **** lol.
i may want to do this as well for my 200k miles maintenance

 

How's Oil and filter / Transmission Gasket filter / fluid or Final drive Fluid or Coolant is connected to rough idle ?

 

One of my customers late husband had a xjs and the xj6,both had been of off the road from about a year ,so she asked me if i could fix and sell the xjs and in return I got the Xj6 ,thats about 16 months ago finally got the time to work on her.Everything has went well until the engine and that,s the surprise because she has always been a great runner.
I have checked and adjusted the cam sensor but no change.She starts revs 20 2000 smoothly then drops to 1100 pauses for a few seconds and then drops to around 500 then stalls.
Gonna do the fuel filter tomorrow.

 

well its not but if the car was neglected and it was a gift. i assume its in need.
if your already doing some fixing up why not go all out?

 

Yes totally she does and Ill do a bit at a time between work ,I always though she would make a nice wedding car.

 

hello.....it's an old post......but have you finally sorted out ?
i have quite the same problems.........
bad luck
thanks
vincent