That's a good one , May have to look at the data plate

 

Been a while since ive posted so I thought Id give an update. Took the car to David Marks garage in nottingham, he has done lots of work for jaguar heritage so I thought hed have the best chance of identifying whats causing the poor idle. I only went for a scan/code read, nothing wrong in terms of live data, o2 sensors, iacv working fine, no codes. He said that an injector service would be a good start along with cleaning up all the ground connections for the engine management system. He also said it wouldnt hurt to start running it on premium fuel due to the cars history. Last owner did 4000 miles in 9 years of ownership, ive done more that in the eight months ive had the car.

He said should that fail, then a valve inspection would be the next step, looking at condition, carbon buildup, again possibly caused by infrequent use by previous owner.

Also Im due to get 4 new tyres, will be putting on new track rod ends as well, Im looking at the goodyear efficientgrip performance tyres, 225/60/16 XL, anyone have anything to say about those?

 

Thank you for sharing, please keep us posted.

 

Not done alot of miles on the new tyres, so Il save my opinion for a few weeks, but I will say they are fairly quiet. Had 4 wheel alignment done along with the new tyres. Car doesnt deviate anywhere near as much, vibration at speed noticeably reduced, only trouble is my steering wheel is now off centre, about 5-10 degrees to the left when wheels are dead ahead. Have the garage not adjusted the tracking properly, or do I need to remove the steering wheel and recentre it?

Il upload the tracking before and after results later, it definitely needed tracking doing!

Also Im thinking of unbolting the intake manifold to inspect the valve condition. I imaging after removing throttle body and air intake, its just a case of unbolting and dropping the manifold to get a look? Or are there other bits to be removed?

 

There is a centering index mark on the round portion on the side of the main left to right casting of the rack .

 

Having a tough time at the moment. Car had been fine of late, but cut out as I slowed for some lights last tuesday, no restart. I loosened the fuel rail and primed several times will no fuel delivery, but fuel pump can be heard when priming. Checked all the common relays and fuses, none burnt or blown. Im now doing the parcel shelf cut method to access the fuel pump as I dont have access to a jack or ramp, and my fuel lines are a bit rusty and rather sensitive (Fuel filter change caused a leak). Has to be the common blown hose issue or a dying fuel pump surely?

 

Fuel pressure regulator bypassing to too much to hold fuel rail pressure ?

 

Was indeed a blown hose
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Thought Id discuss this job a bit more now that the hose is reattached and the car is running.

I wouldnt recommend this over tank removal unless you have no choice, as its awkward, laborious and messy. I did it because I didnt have the means to remove the fuel line connectors.

Make sure you cut the hole big enough, simply so that cuts to you're arm are kept to a minimum. Also helps to do this in a warmer place if you have a full tank. Its about 2C here in the UK and putting your hand into a full tank to retrieve the pump is not pleasant.

Also dont expect to be able to remove the short section of hose that connects to the evaporator ontop of the tank. I spent a good 60-90 minutes with various tools to no avail, the rubber is ridiculously tight on the outlet considering it runs at about 2psi tops, I cut it off and renewed with similar size fuel hose.

 

Finally got round to fitting some refurbished fuel injectors as previously suggested, unfortunately, rough idle is still present, in both park and drive, although I think I did detect a small improvement in responsiveness. Will move onto coils next I think, perhaps just buy a cheap 6 pack for now to see if there is any change. Failing that might have to look at the fuel pressure, and the valves and compression.

 

Was the area of EVAP system covered ?

 

Hi Alster370,

Since the posts related to addressing rust were off-topic related to this "Rough Idle" thread, I moved those posts to start a new thread that I have tentatively titled, "How Should I Address the Rust?" If you prefer another title I'll be happy to change it.

By the way, in all the posts you've made in this thread, I couldn't find one instance when you told us the year of your Jaguar (or even that it is an X300!). Please use your User Control Panel (User CP link above left) to edit your signature and add your Jag's year, model and engine details so they show up in all your posts so others can give the most accurate replies.

Cheers,

Don

 

Hi Don, to be honest I was just going to propose changing the title to "Al's XJ 300" or something as its ballooned into a general issues thread rather than exclusively about the rough idle. I will also edit my signature.

Lady P,

I have ran the car with the evap hose to the manifold removed and blanked, with no real change. Im probably going to do a more conclusive vacuum leak test aswell.

 

The line to the brake booster as it comes out of the upper point on the intake manifold is suspect with mine and there is a trick I can't remember now on how to release it . As a test you can just seal it with some putty .

My EVAP hose was totally missing

 

Found this whilst checking the sparkplugs, dont recall it being there before, could cracks such as these cause the idle stumbling? I didnt check the sparkplug for that cylinder as I could see some oil in the well, but I noticed that the cracks line up with a small bulge in the paint/metal of the well where it goes to the smaller diameter, if that makes sense. The black sealant around the base I thought had initially been put there to hide the origin of the crack, or something similar, but no, must of been someones substitute for the paper gaskets.

Is it worth replacing in any case?

 

The pitting or corrosion in the well lining up with the crack in the coil indicates that you have some arcing coming out of the coil at that point . Bad

As to what point in the engine load range ( different then RPM range ) this is an issue based on what I have seen on a different car . When under a high load on a dynometer I witnessed a arcing that was causing a misfire , but under a no load such as idle or throttle up it was not present , not until there was a resistive load on the drive wheel would it show up . This is because the resistance across the gap in the plug increases with the pressure of the gas in the cylinder as I was told by the technician at the time . But this defies the physics of the gas on a molecular level . But there was the observation .

 

Time to replace that coil, undoubtedly.

I don't use the paper gaskets. I don't really see the point. I was going to create my own rubber gaskets, but I never did...

 

This picture shows the well in question, ive circled the bulge, where the coil sits, the cracks are pretty much in line with it.


I cant hear it arcing, only when I physically pull the plug off of the spark plug. Im wondering if It might be a good idea to buy a cheap coil 6 pack for determining which if any coils are weak or faulty, so that I only need to buy the necessary number of "made in Japan coils".

 

Hi Al,

Do you have any diagnostic trouble codes for misfires, such as P0300 or P0301-P0306?

Personally, I would not waste my money on the cheap coil 6-pack, but rather use that money to buy genuine Diamond Mfg. Co. "Made in Japan" coils to replace any coils for which you have misfire codes. If you suspect you have misfires but have no codes, you could buy just one Diamond coil and swap it in for each coil one at a time to see if the running improves, and buy more Diamond coils only if necessary.

There's always something to spend money on with a Jag.

Cheers,

Don

 

Being in the bottom of the well you might look for some carbon tracking from the tip along the inside of the boot tip , tracking on the plug , verify plug is not the higher resistance exotic plug and only the old fashion copper Champion # X . You can also restretch the spring on the tip contact to get a better contact as well as sand it down . The boot rubber comes off if I remember . The crack you see in your pic comes from swelling of the potting compound inside the barrel which is a indication that it's deteriorated or just heat exspantion . The arcing from the cracks you would think would show signs of heat damage on the plastic . What you see in the upper part of your pic to me would be the shortest path for an arc from the barrel section of the coil to metal but is 180 degees out around the perimeter of the well from your red circle .

If you were to address these issues you might be able to not have the buy a coil . Cheap try .

There is a old school mechanical coil tester with an adjustable gap to fest the strength of the coil and should range in the 30,00o volts , but then they fail as they are heated up in on car driving practice .