spark plug change after lumpy running problem

[Brakebuster]

My wife's X has developed a lumpy running issue, and then the engine fault light came on , as i had a full work load and couldn't work on the car for several days, not even to plug it into the computer, i bought a set of genuine Jag Platinum plugs and the six inlet manifold oval seals , these are specific for the 2.1 V6 , and are different to the 2.5 and 3ltr V6


when i eventually had a day off work i plugged in the Jaguar SSD and a few faults were thrown at me, some for the lambda sensors, and one for the MAF , the good news was that there were not any for the on plug coils etc,

but as i had the parts, and didn't know the last time they were changed as the car has now reached 120k miles on a 54 plate car i felt it was prudent to change them

after some research , the inlet manifold seemed simple to remove, in practice, this was not however the case, yes the visible parts came away quite easily , however , non of the guides mentioned the two loom support brackets under the back , and the back upright support onto the back of the block against the bulkhead, and then a tight ( very tight ) wiggle to remove the intake manifold, here she is removed from the car , mating face already cleaned


IMG_3161 by MyPix on Talk Photography

this is the top of the engine with the new oval seals now fitted , the old ones were very compressed and quite dirty , quite unlike the new ones ( £35 on the net )

IMG_3159 by MyPix on Talk Photography

i was pleasantly surprised at the overall condition of the engine components , given the miles on her, though some of the steel brackets at the front behind the rad have suffered from surface rust ,

a wider view of the engine shows the rear coils which are not accessible with the inlet manifold in place, and can be neglected come service time due to the amount of work to access them

IMG_3158 by MyPix on Talk Photography

yes, i did break that plug

removing the coils is a POP , one bolt and away they lift, ensure the spring contact inside the insulator is intact and looks' good ' ,


IMG_3160 by MyPix on Talk Photography

removal of the spark plugs is as simple, especially using a correct spark plug socket and cranked handle wrench ,
the new plugs got a thin smear of copper slip , hand tightened and then a 16th turn with the socket set , pop back on the coil and again lubricate the bolt thread and gently but firmly tighten down so everything is ' square'

here are the old plugs, i think they have done a good job and now it was time to retire them , cylinders 1-6 left to right , gapping was all over the place on them though ( usage and possible installation ? ) with 120k miles, these should be the second set, but could easily be the originals....what do you think ?


IMG_3162 by MyPix on Talk Photography

for those wondering, the engine is numbered left to right , back right #1 , front right #2 ( from the drivers seat as ever )

i also found a severely split engine breather pipe from the top of the front cam cover to the inlet manifold behind the TB , a temporary repair will suffice for the time being as i have ordered a new one from jag, this would have been upsetting the MAF as air was entering the system after the MAF and the TB , this split was hidden under the plastic top engine cover


once everything was screwed back together she fired up first time, and runs much smoother, and the MIL light also disappeared after a few miles of driving,

i have bought another MAF sensor and will see if swapping it out will make any difference

in all about four hours of work, but well worth it knowing i have new plugs and seals installed


BB

[J44EAG]

Plugs very worn indeed, Vince. Only one there that would appear to have anything like the right gap. Judging by the state of them, I would say they are original to the car with some of those gaps being at least three times what they should be.

The small bore air pipe elbows are probably the same if not similar to the V6 S-type, which crack, split and collapse for a pastime. On an S, the plug change interval is 60k with the two air pipe elbows being an almost dead cert for needing replacement at the same time.

Worth also checking the air assist valve which is a sliding ported piston affair which needs to be free running and allows the injectors to have the correct proportion of air shroud adjusted in direct relationship to the speed of injector pulsing. I`ve seen one valve seriously sluggish due to corrosion internally. That particular car ran very badly until I had managed to free that off.

The work involved removing that manifold will scare most people. On the S-type it is not unusual to find the exposed plugs in better condition than those under the manifold. Often people just walk away from the issue in funk and just the easy three plugs get changed. eventually the long over used plugs fail and something has to be done to correct the issue.

Keeping the throttle body throat and butterfly plate clear of crank case breather sludge also helps with a good idle and pick up from a standing start. But then you already know that!

If not already changed, replacement of the engine coolant sensor would be prudent at 120k miles. I`ve found a tired sensor can completely mess up fueling. When they fail the sensor can throw the temperature gauge to full deflection hot and cause cold start problems kidding the ecu that the engine is hot when the engine is in fact stone cold. You might remember the incident I had at Weston Park some years ago when my sensor failed. For a tenner, changing one is a good idea to preserving general reliability.

Nice job, Pal. Much more involved than doing a V8 plug change but you know that as well!

Mike

[oldtimer]

Well done BB,
It might even get you to Kemble for breakfast.

Some thing that never gets mentioned that you BB may care to comment upon.
The HT will always want to find a route to earth. As the plug gap opens beyond the design gap through fair wear and tear the HT is still looking for that route to earth. In earlier times the HT would escape through the walls of the HT leads - run the engine in the garage one dark night and see the leads illuminate. I am of the belief that the same applies to the coil on plug but instead of escaping through the plug lead it takes the coil pack out. What do you say ?

Because of this belief I have the necessary parts on the shelf which I want to complete before 50K presently at 45K

Oldtimer

[Brakebuster]

Thanks for the replies boys,
some very good advice on other things to look out for , when I find the location of the coolant sensor, I will swap it for a new one, little and often keeps the bills down and the car healthy ,

after some more reading , it seems the split crank case breather pipe might have been the major cause all along, Jaguar actually provide a revised design for this part now, as the original got hard and split allowing unmetered air into the system, which throws the engine fault light , I will however still hang on to the spares I have and change them as and when required ,

Phil , hmm , on-plug coils, a fact of life these days for the majority of petrol cars, and I have had them fail on brand new cars as well with only 6k miles, I think they are built to last just long enough , but can fail at any time, no knowing why I'm afraid , though your theory seems sound ?

thankfully these days , they are readily available , however, the jag ones for my X were £95 each , so a trip to the local breakers bagged me three ( unknown condition mind ) for a fiver , worth a punt in my opinion , even just to get the car going if I have to buy brand new in the long run


BB

[J44EAG]

Provided you can source new, preferably OE plug on coils from alternative sources and make savings in the process, I see no reason for buying Jaguar OE units at inflated prices. Yes, they may well have a two year warranty included instead of a one year from another source, but you don`t half pay a premium. £95 each? Cor....someone is having a laugh surely! i`d take a flyer on a handful of used ones for the price of a couple of pints and pick out the best of the bunch!!

Phils explanation is all good in my opinion re causes of failure.

Coils burn out rapidly if a plug beneath it begins to break down. In my experience, misfires across the whole rev range point to a duff coil or two. Misfires at say 1500rpm and then perhaps at 2300 rpm lead me towards duff plugs. Immediately I have experienced any form of misfire, I substitute a known good coil on each plug in turn. No change on one plug when the new coil is fitted leads me to suspect a duff plug.

Despite my new to me XJR having a Main Dealer service record, the quality of the air filter I removed meant that I could not trust that record in any shape or form. I bought the car at77,800 miles and new plus should have been fitted at the 60k service. What I removed at 79,100 miles were certainly not 19k spark plugs. All gaps opened out by at least 0.5mm if not more. So new plugs were installed and low speed hesitancy has been eradicated. As always with plug on coil cars, I have a new spare plug on coil in the boot in case of trouble on the road.

At Weston Park a few years ago I experienced both coolant sensor temperature and a burnt out coil. In disgrace the car was abandoned in the middle of the field for the day. That evening a new coil was fitted which made the trip home more pleasurable even with the temp gauge showing fully in the red for 250 miles. Sensors are £28 from a Main Dealer WITH Club discount or an Intermotor ebay sourced equivalent, all be it with just a one year warranty for just £9.82 delivered to my door. That is one third of the price of a Jaguar part and I don`t have to travel to Southampton or Chichester to collect it!

A coolant sensor should reliably last around 100k miles. Plenty do even more mileage than that. I had one give up at 70k miles so the XJR at 79k will have it fitted when I do the next round of maintenance shortly. The new part will be installed and the still working sensor will join my road going spares department in the boot. Seems a good part to have in reserve given my Weston experience. Like an Irishman wearing two condoms, it pays to be sure to be sure.

Mike

[oldtimer]

Mike,
Have you ever tried cutting the tip off a sender to see what's inside. Next to "naff all" in there. The clever bit is the little thermistor in the end , looks like a black sequin. As the temperature rises the resistance decreases.

The older gauges (don't know about current stuff) which are sometimes referred to as hot wire gauges have a bit of peso wire wound around a bimetal strip, so as water temperature rises sender resistance reduces which in turn allows the peso wire to heat up and deflect the bimetal strip which in turn deflects the needle of the gauge.

Have been to the Intermotor factory many times, they used to be a supplier to you know who. I'm sure they have renamed themselves now

P

[Brakebuster]

Mike,
Have you ever tried cutting the tip off a sender to see what's inside. Next to "naff all" in there. The clever bit is the little thermistor in the end , looks like a black sequin. As the temperature rises the resistance decreases.

P

that depends on whether its a PTC or NTC Thermistor ,


BB

[J44EAG]

You are a daft pair! No wonder AV8 let you in the door. In 1995 my eldest daughter nicked my BMW and crashed itand crashed it in the flower bed outside. She wanted an ice cream so took the car. Only twelve at the time!!!!! I did my LAME training there and stood an Auster on its nose when the brakes failed!! A pretty normal occurrence with one of those flying heaps.

Phil. To see inside a modern sensor, I tactfully suggest you cut the end off your own. These things are expensive but send me a tenner and I might cut the end off one of mine and write an article about it. Mightily bored you will all be too.

Mike

[oldtimer]

Mike, Not as boring as most of the TV

BB. I told you I know nothing about the modern stuff. You can get your class notes out and explain over breakfast the difference between PTC & NTC. Hopefully nobody will crash into the flower bed and disturb you !