Hi,

Ok I am reaching out for help here with my 08 XKR 4.2. So about a month back oo my usual Friday I went out and just on the starting stretch of some dual cartridge way went large and I was met with surging and miss fires, limp mode and the appropriate dash lights, flashing engine warning and plinking sounds. She continued on limp OK, a stop and start and trying anything did not sound good and same results. So I thought maybe duff plugs, coil packs and new before as I have posted here about fuel smell. I had found a breather of the SC that links to the fuel pressure sensor was not connected and the pipe degraded so that was replaced. List of things done:

New fuel filter
New Brisk quad elctrode racing plugs
New coil packs x 8 these are a replacement over Jag made replace again
working on VVT solenoids drivers side done doing passenger side. Which involves new VVT solenoid, gaskets for spark plugs, VVT and cover gasket
Working on replacing Oxygen and Lamda sensors only managed 2 so far as they seem rusted in
New fuel pressure sensor

Its already has new air filters, the codes from my diagnostic gives generic p0300 misfire codes and not much else , it does report misfires in fire 1000 rpm so wondering what else or things to check.

I tried some Cataclean to the fuel

There is no trouble starting either which is odd, due to how crammed in everything is was thinking could it be bad injectors or drop in the fuel pressure ?

Any advice is welcomed it makes a sound similar to the video in the VVT section:

https://www.jaguarforums.com/forum/x...obably-255674/

 

I have bad news for you...

 

Check your fuel trims as well to see if over/under fuelling.

 

+1 fuel trims in case air leak

Don't keep letting the MIL flash as that's severe cat damage occurring

 

Thanks I have new CATS coming as manage to find some new ones at a great price, any advice on how to check the fuel trims please

 

You're not listening to your car. If she's only throwing P030000... Cats probably have very little to do with it.
Were the codes thrown before you changed coils and plugs... Were these OE?

 

Yes it threw these before I put in new plugs and coils. I have been suspecting fuel / fuel pressure. I am willing to spend on her as I don't plan on selling it

 

Spend $60 on Amazon for the Autel AP200 with the JLR download. Mates to your phone.

Among **many** other things it'll give you real JLR error codes, your actual fuel pressure, your Fuel Trims, which cylinders are misfiring and probably a good number of other items that can help give you real data. Among other things, you Trims data will tell you if you have a vacuum leak, so you can smoke test it. Note that a 20 year old 4.2 engine likely has numerous dried out orings and perhaps small cracks in hoses here and there.

If you don't have the 4.2 maintenance manual (4000 pages), DM me and I'll arrange with you to get one.

You've fired the parts cannon at it. Now accumulate some real data to work with.

Good luck.

 

Thank I have a comprehensive disag tool just not had much real play time I have found I can check the trim on it and do injector test plus more. So once I finish with the passengers VVT as a bunch of stuff is off at the moment I will get in to the data

Using the XTOOL D8 to Test Fuel Injectors

Now, here's the part most car owners overlook: modern vehicles rely heavily on computer-controlled fuel injection systems. Without a scan tool, you're working blind.

The XTOOL D8 is a professional-grade OBD2 diagnostic tablet that I personally recommend because it combines advanced functionality with an easy-to-use interface. Here's how it helps with fuel injector diagnostics:

Key Features for Injector Testing

•Active Tests (Bi-directional Control): The D8 allows you to send commands to the ECU to open or close individual injectors. This means you can perform a balance test without expensive shop equipment. If one cylinder doesn't respond when the injector is triggered, you've found your problem.

•Live Data Stream: You can monitor real-time engine parameters like short-term and long-term fuel trims, RPM changes, and injector pulse width. Abnormal readings will confirm injector issues.

•Diagnostic Trouble Codes (DTCs): The D8 can pull and clear check engine light codes. If your car is misfiring, you'll likely see P0300-series codes that point you toward the affected cylinder.

•ECU Coding and Special Functions: Unlike basic scanners, the D8 supports coding and advanced functions, giving you dealer-level diagnostic power.

 

To be honest I’m not quite sure how the ‘active tests’ would actually show you anything, since spray pattern and flow isn’t something you can measure with the injectors in the car.

Start with seeing if you have an air/fuel delivery issue first by checking short and long term fuel trims. If one bank is off massively, you know where to zero in.

if those are fine and you appear to have proper fueling and air delivery, you can move to checking spark/timing (sensors, plugs, coils).

Remember there’s three things needed to run an engine and they all are equally important.

look forward to hearing back on your findings.

 

For nearly all the cylinders to misfire check fuel pressure to the injectors. The regulator may be suppling less than, the "about" 55 psi needed.

 

These cars are a bit more complex, but the basics of what the PCM (aka ECM) is doing are like the attached picture.

 

If any one needs advice on replacing the VVT solenoids I can tell you and its a b*astard job and you need a special tool to remove the main fuel line as it uses a spring lock coupler (drivers side here in the UK) when you have the tool that eases the issue, next is the studs as these hold on various bits and the main one is the dipstick tube this goes over the stud and you cant putt the tube out to get it over the stud. all you need is 7mm 8mm, 10mm long and short socts along with the tools. You will need solenoid seals, spark plug seals and rocker cover gaskets. Likely did not need to do this but the old gaskets and seals were hard so glad I did.

Anyway once back together I could start the car, still rough idle. I was able to measure the short trims and found both side were all over the place, from +15% to -15% and I know they should be 0 or 5% at the highest. I can see cylinder 4 is mis firing consistently cylinder 3 had maybe 5-6 but at first had 0 along with the others. At least I know where to focus should be. Any pointers?

My plan is to replace the coil pack and different plug on that cylinder, maybe a compression test as well. Then I think it could be injectors

 

A slight order change. Compression check, replace plug, switch coil to another cylinder. Run engine and if same cylinder misfires, replace injector.

 

Agree with Sony, I'd also add in checking for vacuum leaks as an easy step.

 

Awesome thanks will give it a shot

 

So thought I would give an update, we got some better weather so had a chance to look at this, I used plug test and could see the coil sending spark to the plugs, I pulled the plug and could see it was black likely from the unburnt fuel so stuck a replacement NGK in there, I also did a compression test after pulling the fuse from the fuel pump and letting it stall. The compression test was fine and good compression. Now she is idling smooth but the trims are still all over the place varying between +15% and -15%, under load I now seen minor miss fires and multiple cylinders including number 4, before number 4 missed all the time but not now at idle reports 0 missed. I also put some PIC-24 injector cleaner in the tank.

My CATs arrive today so they will be removed, replaced with the new ones and new oxygen and Lamda's as noticed one did report on a recent diagnostic where it did not before. Will update again

 

So I have spent the past week under the car, I removed the old cats which were in pretty good shape on the out side. I had put one new oxygen senor in but as the lamda's and other senor were in so tight they were not possible to remove on the car, I had a 22mm spanner, and the special socket but no joy.
There is 2 15mm nuts holding the cats on you do want to remove the cross brace (V Shape) which is 6 bolts as this give more room. Be advised the clamps holding the cats to the exhaust are tack welded on which sucks. replacement studs and bolts were £30 odd from British part/ SNG Barrett. Once free and the clamps undone its wiggle time along with lots of WD40 and they will slide out, if original then no exhaust glue is used. To also add there is no gasket or seal from the manifold to the cats I found this out on another thread, the bolting together presses the cat trumpet to the manifold and that is what seals it.

I had 1 stud come out which I replaced and used new nuts where I could, fitting the drivers side (UK) was more tricky, I had put the new sensors and Lamda's in prior to refitting, I should add here as well the connectors slide onto these thin metal pieces which you can remove 7mm nut one side and 8mm on drivers side, you need a fine flat blade to lift the piece holding the sensors connector to the metal tab.

Once all fitted and connected up I fired the car, yes with no exhaust after the cats, my neighbours are probably pis*ed with me but my god does it sound good :-), I chucked on the diagnostic and short term trims are at 2-3% positive and no miss fires even under load. I had noticed when i removed the sensors from the old cats before they were sent off some whitish powder fell out of one of them. So could it be a dirty cat or bad sensor I don't know but happy she is now very loud but running right. Time to spend "K on a new Paramount performance sports exhaust :-)