Have had the p38 for a year now, has been wonderful.
Last week I noticed that after parking and engine cooling down a bit and back on it would slightly shake at idle for 10 seconds then go away. It has been driving fine after that. Also last week got a misfire on cyl 5 (p305 code), the service engine light was on. I cleared the code and has not popped up again (been about 200 miles). It also has been ticking only when warm, it sounds fine when cold and then will start a tick. I got the stethoscope out and its on the right side of the engine but can be heard almost louder on the right side tire well and under the car. Anywhere I put the stethoscope on the right side can be heard. Read the codes today and the p305 was not there but now have a p300 which I know is multiple misfires. I also took it for a drive with the nanocom plugged and it would throw misfires of cyl 5 (but the service engine light has not turned on and when I read codes with the nanocom it shows none)

I have read everything I could on the internet and a lot of cracked block/slipped liner. I want to figure this out myself and see if maybe its not something else because I go into catastrophe mode. Plugs, wires and coils have been done in the past 10-20k miles by the previews owner. Head Gaskets were done about 50k miles ago.

Video of the tick - https://imgur.com/a/p38-tap-I1WRgts

Thank you!

A misfire on one cylinder when initially starting can be caused by a liner to block leak allowing coolant into that one cylinder but that would normally be accompanied by losing coolant and/or pressurising the cooling system. Start by taking the spark plugs out and seeing if number 5 looks any different to the others, if coolant is getting in there it will look steam cleaned or will have an orange tinge to it caused by burning coolant.

Thank you.

Will pull the plugs and look. Coolant seems to be fine. I will say I did have some loss of coolant but I topped it off 3 months ago and seems to have stayed put, I do know I have a small weep on the radiator (have a rad that is ready to go in). I did also check last night and seems like I do have some arcing on the plugs, its minimal but its there when eyes adjust you can see its arcing on all the plugs. I will be replacing the wires for sure.

Also, small exhaust leaks can sound like engine ticks, especially manifold to head attach points. I recently replaced an exhaust manifold on my Disco 2 due to it being cracked. It did have a very slight ticking sound.

Would that cause misfires too though? Also the tick only happens after being warm, would a leak not make the noise as soon as car is started?
What would be a good way to look for exhaust leaks?

It wouldn’t cause a misfire (unless the leak is very bad and fresh air gets to your O2 sensor). I’m not saying this is your issue, just that small exhaust leaks can present themselves as ticks. Like you did before, you can use your stethoscope and probe around with an exhaust leak in mind.

Harv wrote:

It wouldn’t cause a misfire (unless the leak is very bad and fresh air gets to your O2 sensor). I’m not saying this is your issue, just that small exhaust leaks can present themselves as ticks. Like you did before, you can use your stethoscope and probe around with an exhaust leak in mind.

Thank you Harv. Will poke around this weekend!

The tick actually doesn't sound too bad. I've got 2 P38s (both 4.0) and have just sold a 4.6 and all do it to a certain extent. Mine was doing it when I bought it at 205,000 miles. At 287,000 the engine was completely rebuilt at V8 Developments and when refitted it, it still did it. As it sounded louder from underneath the LH side, I decided it must be from the torque converter or gearbox. At 454,000 miles the gearbox died so that along with the torque converter were replaced. Still does it, no worse, no better than it was when I first got the car.

Gilbertd wrote:

The tick actually doesn't sound too bad. I've got 2 P38s (both 4.0) and have just sold a 4.6 and all do it to a certain extent. Mine was doing it when I bought it at 205,000 miles. At 287,000 the engine was completely rebuilt at V8 Developments and when refitted it, it still did it. As it sounded louder from underneath the LH side, I decided it must be from the torque converter or gearbox. At 454,000 miles the gearbox died so that along with the torque converter were replaced. Still does it, no worse, no better than it was when I first got the car.

Thats good to hear (no pun intended haha) but I posted on facebook group and at least 3 people told me cracked block, its over which I think its pretty hard to diagnose through the internet so its good to hear some think it might not be that. I am definitely conducting some tests when I can. First order of business is new spark plug wires to get rid of the arcing which is definitely doing and could be the source of the misfire.

Any recommendation on brand of wires? Right now has STI wire which are apparently pretty popular in discoveries but not sure I should get the same brand, they are about 2 -3 years old.

hi just a question, did the tick just start or has it been there for a while, it sounds too fast for a single cam lifter. it may pay to take the tappet cover off and check the rocker assembly as the rocker assembly it can pull threads and create rattles which would explain the fast rattle sound you have. your rattle noise is a bit loud and fast for a small nuisance rattle IMO.

mad-as wrote:

hi just a question, did the tick just start or has it been there for a while, it sounds too fast for a single cam lifter. it may pay to take the tappet cover off and check the rocker assembly as the rocker assembly it can pull threads and create rattles which would explain the fast rattle sound you have. your rattle noise is a bit loud and fast for a small nuisance rattle IMO.

Not that long, I would say maybe 3 weeks is when I first noticed it.

Removing the cover is in the future plans if I don't get an answer from the spark plugs and coil wires.

Cracked block is highly unlikely.

For sure your arcing wires will contribute to your misfire. Wires are very easy to change on GEMS engines (pre ‘99). On Bosch engines some disassembly of the upper intake is usually required (though some people can do the job without disassembly).

Harv wrote:

For sure your arcing wires will contribute to your misfire. Wires are very easy to change on GEMS engines (pre ‘99). On Bosch engines some disassembly of the upper intake is usually required (though some people can do the job without disassembly).

Mine is Bosh and looks pretty tight back there :) I will try to not have to dismantle the top of the engine, will use all the tricks in the book but we will see, I don't have kids hands. It will be the first order of business as well as look at a couple of spark plugs to compare to the one that is misfiring.

Also thank you all for the help, I really appreciate it!

Let us know how it goes. Removing the upper intake isn’t very difficult or time consuming.

I have bought some new wires to eventually get these done. Since I am really busy with my job for the next weeks I decided to just get some dielectric grease around the plugs to see if it helps with the arcing (I have half an hour but not more unfortunately). As I unplugged the wires I noticed this around plug 5 (the main offender of the misfires). Looks like either its an old leak (I have asked the previous owner since he did the spark plugs and he woulda noted this) or its a current leak, its almost too much coincidence that it is on plug 5 which is the one misfiring.

Quick search and seems to be probably valve cover gasket? I do still need to remove the plug and look at it, hopefully I can do that this weekend. But I will have to remove the intake anyways to do the wires so would get in there and do this as well.

Not sure what you are looking at but a leak from the valve cover would be far worse than that slight staining if that is what you ware referring to. What plugs are they? LR suggest Champions but modern Champions aren't the same quality as 20 years ago Champions were. Most of us run NGK plugs.

You've got that horrible SAI system to fight your way past too....

Gilbertd wrote:

Not sure what you are looking at but a leak from the valve cover would be far worse than that slight staining if that is what you ware referring to. What plugs are they? LR suggest Champions but modern Champions aren't the same quality as 20 years ago Champions were. Most of us run NGK plugs.

You've got that horrible SAI system to fight your way past too....

I talked to old owner and he told me that there was no stain there when he did the plugs so this seems to be recent and the cause of the misfire on cyl 5.

The plugs are indeed champions, do you think I should switch that one out to NGK and see what happens? I need to pull it and see how it looks. What other reason could be for that leak?

Finally had some time to pull the spark plug.

Half the ceramic is black, rest is white. Also I noticed that the gap is pretty closed, not much of a gap really.
What could this mean? I have read that could be piston that slapped it close? or could be detonation? (maybe the half black could explain this?)
No codes but when I live read misfires its still doing it but now seems like the cyl that was misfiring a lot is not really doing it and now just getting a misfire on cyl7 but very randomly, get 1 misfire there and then nothing for a while then eventually get 1 again. But no codes at all.

Those plugs look to be copper core (fat centre electrode) whereas the recommended NGK equivalent, the PFR6N-11, have a Platinum centre electrode. The first thing I would do would be fit a set of those and see what difference that makes.