but I just started getting the dreaded 45-55mph bucking misfire. I know I need to check and see if the tensioners ever were updated. I've had the car for 4 years now and it had 82k miles on it when I purchased it. It has 96k on it now as it has been mostly sitting and over the last year has only been driven on weekends. My question is shouldn't it be misfiring and bucking all the time if the timing has actually jumped a gear as described in the misfire guide here on the forum? It only does it to me on a hot day when the car has been driven for more than 30 minutes. I'm about to go through the car and check the chains in addition to doing sparkplugs and testing the coils and get the transmission fluid and filter changed and then I plan to drive it daily going forward. The tensioners and guides will be replaced regardless if the plastic ones are still in there. I just wonder if I'm missing a detail with when I'm noticing the stutter? The car has had a new rear electric module and new fuel pump installed in the last year and I recently did the brakes myself. It just seems like a waste to let the car sit.

 

No car info!! We are stuck!
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Oh sorry, I didn't even realize I didn't post it!

It's a 2000 S-Type V8.

 

If there are miss-fires the odds are you have stored codes.

So first run down to the parts store and get the codes read for free. Before they unhook the code reader make SURE they erase all codes. Before spending any money you want to be sure the problem repeats.

Post back with what you find. But be aware the misfires could be from the timing jumping on the gear to. But hopefully it just needs coils and plugs and cam cover gaskets at this point.

Then you will need to make a decision about the tensioners and chains.
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I don't have any oil leaks, which leads me to believe it's already been done before as I would think it would be leaking by now, but I will check soon. The only leak I have is a very small power steering leak that I recently noticed. I know it's time for plugs and I'm leaning towards coil as the issue because it is so intermittent and seems dependent on temperature. I don't have a check engine light on and that's what is throwing me off. I've yet to read about anyone having this issue without a check engine light.

 

You may get little to no warning about tensioners and it wouldn't be via an oil leak. You need to take off enough items and look at them. If plastic they WILL fail at some point and commonly the engine is not worth rebuilding.

 

I fully understand what you are saying and was more than prepared to just get it done, then I saw the price to get it done.. I may leave it sitting. It's rarely driven and has become a money pit over the last year

 

There are spark well gaskets within the cam cover itself. You might not have an external leak but in fact the cam cover spark well rubber gaskets could be leaking oil into the spark plug well shorting out your coils.

As mentioned - Get the codes read, then look at that coil(s) (remove 6 bolts holding the coil cover in place and pull the coil) any wetness at all or any dried oil residue and not only should you change that coil but all associated cam cover gaskets on that side of the engine.

Don't assume cause you haven't seen an oil leak externally - that oil leak issues aren't lurking beneath the cover...

 

That sounds like a good possibility. It seems like that could explain why the car takes so long to start acting up on a drive while the oil pools. I'm going to replace the spark plugs soon so I'll check for oil seepage while I'm replacing them.

 

Being a little nitpicky (not sure either) but "could be leaking oil into the spark plug well shorting out your coils." - I believe oil does not conduct electricity and shouldn't cause a short per se. Oil would foul up the spark plugs for sure.

 

The oil tends to have a lot of carbon, acid and so on in it. They conduct. It ruins coils, which is why people keep having to replace them when they've been cooked in the "oil".

 

One other comment. You could have stored codes without the check engine light being on.

Miss-fires area a statistical thing and you must exceed a certain threshold before the light comes on. Many miss-fires and the check engine light will flash. This indicates you could be damaging the catalytic converters and you should stop driving until it's repaired.

Even when everything is operating properly there is a small percentage of miss-fires because the combustion process is not perfect.

So the aftermarket code scanners are crude tools compared to the factory service stuff. They can see miss-fires on a level that the consumer code readers will never pick up.

The oil is on the outside of the plugs. What happens is you create a path to ground. Remember this is dirty oil. Not pure clean oil. So the high voltage will eventually break the oil down and arc to ground. This builds carbon tracks from the coil boot to ground.

So yes you are right but the fluid is usually dirty oil and can have some water mixed into it to. This is because the coils are really not sealed but only shielded from water coming in from outside the engine. You have seen all the threads about not washing the engine. This is partly why.
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An update. I pulled the coils today and there is no oil leak. Everything was very clean. I replaced the plugs today and will drive the car daily starting tomorrow. Two of the coils were previously replaced as I could see based on a slightly different part number. If it isn't an updated Jaguar coil, it may have been a Ford part number as the part number followed the same format. If the misfire persists which did not happen on my short test drive I'll get a tester to see which cylinder is misfiring and replace the coil. Thanks for the help on what to look for. A couple of the plugs looked very rough, the two rear cylinders.

 

Still having the random misfire, though sitting idle feels perfectly smooth now most of the time. I found a deal I couldn't pass up on new OEM coils and bought 8 new ones. I'll hopefully have them by this weekend.

 

I don't mean to hijack, but has anyone bought aftermarket coils before? I'm looking at a set of 8 for $200 and they look OEM but states aftermarket with 10yr warranty. On the other hand, I could get 8 Bosch for $90 but the height on the top of the plugs looks much taller and I don't think I could fit the covers over them.

 

Aftermarket coils are not the answer, neither is buying 8 OEM coils to chase down 1 or 2 coils that are acting up.

Just my $0.02

 

They are OEM coils that I purchased, brand new. The deal I got would have not been near as good if I only bought 2-3 and for not much more I'm going to replace them all.