Ok thought I had a gearbox issue had the car to local transmission shop for diagnosis nothing found they said the problem is in the engine.What happens is if I drive the car normally I have no problems but when I ask for more power usually 2500 rpm upwards the car starts too, what i think is a misfire not sure and I get a rattling noise. The car seems to hang in gear as well until I back throttle off. I've changed the coil packs still the same.So far I've had no dash messages or fault codes to work off.Anyone got any ideas what I could investigate next.

Many Thanks
Steve.

 

OK all coil packs changed along with spark plugs still got misfire. Have now managed to get a code P0306 misfire on cylinder number 6. Also when car is in park engine revs cleanly up to the limiter so misfire is under engine load only.Could this be a symptom of a blocked or bad fuel injector.Also noticed mpg has dropped from around 17 to 14.
Scratching Head
Steve.

 

Cylinder No. 6 would be the culprit then. Is the No. 6 coil pack receiving any input voltage to it? Please post the year and model of this vehicle.

 

This is a long shot however when you mentioned "rattling" could that be engine knock/preignition?

If it is could that be connected to a physical issue with that cylinder? Others with more expertise might chime in.

 

Thanks for the replies.Car is 2005 XJR 130000 miles. I have a spare coil pack and spark plug If I put the connector on cylinder 6 on the spare coil pack would I see the spark plug light up when the engine is running ?

Cheers
Steve.

 

OK so this morning put a coil pack and spark plug onto cylinder 6 to check for a spark.All ok. Could someone confirm firing order for this engine . I can't think what else it might be as it only happens from around 2500rpm upwards.Anyone got any ideas what to check for next if not its going to have to go to a garage for expert ? advice.

Thanks
Steve.

 

Firing order 1-5-4-2-6-3-7-8

303-07B : Engine Ignition – 4.2L NA V8 – AJV8/4.2L SC
V8 – AJV8/3.5L NA V8 – AJV8
Specifications
Specifications
General Specifications
Item Specification
Firing order 1-5-4-2-6-3-7-8
Spark plug type - Vehicles with supercharger NGK-IFR-5N10
Spark plug type - Vehicles without supercharger NGK-IFR-5N10
Torque Specifications
Description Nm lb-ft lb-in
Spark plugs 27 18 -
Ignition coil-on-plug retaining bolts 5 - 44

 

Can anyone confirm the cylinder number layout please. I want to make sure I"m on the right cylinder.

 

Invest in a COP tester

 

https://www.google.com/imgres?imgurl...0igl8vUjAeQCHM

 

I apologize my post was incorrect on the firing order. It changed for MY 2005. My post was for 2004 MY.

 

Try verifying that the No. 6 fuel injector is working properly by listening to the injector solenoid clicking on and off with the tip of a long screwdriver placed against the injector body, or with a mechanic's stethoscope.

 

Thanks for the replies guys.I think it could be either a faulty injector or after looking around the forums possibly a damaged or collapsed cat.Anyway its of to the local indie tomorrow to see what they can find.

Cheers

Steve.

 

Latest update.Just got back from diagnostic check at a Jag dealer.Came back with the same codes I found P0306 Cylinder 6 misfire and P1314 Misfire rate catalyst damage bank 2.The only idea from the Jag tech is the fuel injector on that cylinder is stuck wide open or something wrong with the wiring on cylinder 6.Fuel injector staying wide open would explain the 3 to 4 mpg drop, he thinks it could be drowning the spark out. If I have got to remove the injectors I do believe the supercharger has to come off.If this is the case I will renew all parts needed but I do not really want to do this if its not necessary.Is there any way of checking the injectors without removing them ? Or is it a case of bite the bullet and tackle the dreaded egr removal along with supercharger etc.

 

In my corner of the world I would be inclined to think it's a fuel octane issue (low octane value or bad fuel). The rattle is likely engine knock under load. I'm guessing there are knock sensors on these cars and that the ECU will pull timing to prevent serious engine failure. I would try running a couple of cans of octane booster through the engine and switch to a different gas station before tearing down the engine or replacing the coil packs.

 

That was my thought too, and I've always been taught to try the cheaper fix first. Of course if your riding that close to the edge of a misfire then there probably is a more serious issue like fuel injector etc.

 

Car is having a Terraclean tomorrow. If this does not work then a strip down is coming to get injectors out for inspection.

 

soft carbon build up
If you do have to take the super charger off then consider replacing the coolant hose under it and possibly even the knock sensors.<br /><br />Also look at the elbow below the throttle body and see if it is covered with soft carbon.<br /><br />If it is then the charge coolers are basically inoperative because they will be as bad with build up in the narrow passages of the cooling matrices.

 

Thanks Jackra.Yes this is what I intend to do if the charger has to come off. What ever needs replacing it shall get replaced.Earlier in the year I had a lumpy tickover which was caused by a sticking egr valve.I stripped the intake system down and removed the throttle body to gain access to the egr. Then came the dreaded hidden bolts. I ran out of time because I needed the car back on the road. A can of cleaner into the intake solved the problem for know.

 

Car was Terrecleaned today made no difference.So started to pull car apart now to get to injector number 6 and whilst I'm at it replace all other parts under the supercharger as well.Now to find a list of parts required.

Wish me luck (egr)

Steve.