Left my 2003 V6 Sport sitting in a parking lot for a few days. Started right up but as soon as I got on the gas it started bucking. At first it felt like a clutch or gearbox problem. Drove around the block, it got better when I revved up the engine but started to get much worse at low revs under load. Then as I pulled in the garage it even started misfiring at idle.

Plugged in my OBDII tool, strangely no codes at first, revved it up again and finally it threw P0300 and P1316 when the car sounded like it ran on 3 cylinders.

Thinking it's a repeat of my plugged cat converter issue from a few years ago, I pulled the O2 sensors but no help. Hmm then I thought vacuum leak, checked all hoses, no issues. Then I thought maybe clogged fuel filter, replaced it, still no help (although it did need replacing).

Then finally I started pulling coils and plugs and found the problem. Somehow water entered the top of the valve cover and into the spark plug holes on the driver side bank. Quick smell and taste test confirmed it was neither coolant nor washer fluid. Just plain water. Dried out the water using a few Tampax. Immediate improvement but still some misfires at idle. Narrowed it down to one coil that must have gotten damaged from being shorted out. Replaced coil with a new one and all is good again.

Thinking back we did have a few days of torrential downpours. Clearly the engine cover and the coil boots were no match for the heavy rain. They actually made things worse by keeping the water locked in instead of letting it evaporate.

Just wanted to share yet another design flaw that's a possible cause of engine misfire.

 

Or you have a misfitting / perished seal.

The cars from new were fine with such rain so yours has developed a fault...

 

Rain generally falls within 45 degrees of vertical. I'm having hard time understanding how this time it managed to twist and turn to end up under a hood and engine cover reaching the plugs.

Your car may have a fault, but it's not a design issue.

 

Enough heavy rain running down the windshield always ends up under the hood. It is supposed to channel to the corners and drain down under the car but it didn't - design flaw #1. Somehow, perhaps due to the angle of the parking lot (RF corner was lowest, LR was highest) the water ended up in the U shaped valve cover which inexplicably does not have a drain hole - design flaw #2.

The coil boots have tiny openings at the top - design flaw #3. And naturally they lose their ability to make a good seal with age, but they do an awesome job keeping the water locked in once it's there.

I will probably just remove all the coil boots so next time any water that may find its way in will have a way to evaporate away.

I have owned many cars in my time but never had rainwater in spark plug wells. Jag/Ford keeps the surprises coming..

 

https://www.jaguarforums.com/forum/s...tr-rain-69885/

This has been discussed for many problems with rain entering the engine bay.
Above link is just one of many threads I could find. Sealing the hood cowl is a way to correct the problem. Many suggestions on the forum on how to do it.

 

That only applies to the STR, and because of its unique layout.

The OP's arguments for his 3.0 would mean we'd have hundreds or thousands of posts for the 3.0 like his. We don't.

It's because his car has developed a fault during the last 13 years. Maybe a seal has perished - 13 years is a while.

His car has (should have had) plugs replaced but sounds like the plug wells were not sealed after that - bad work by someone.

Rather than the OP alleging design faults, finding out how the car SHOULD be and fixing it would be more use.

 

https://www.jaguarforums.com/forum/s...e-today-16749/

I know this is a V6 model. As is the above car. Most of the problems seem to be with the TPS causing limp mode. Never know what else a lot of water could do. It seems more coil related but the OP mentioned that he is positive that water was in there and I will give him the benefit of the doubt. Many threads over the years about water entering the engine and the trunk and sometimes even the ECM getting wet.

 

Perhaps it applies to the V6, too. I doubt the cowl is that different. The rubber on my cowl has seen better days. Might be part of the problem actually.

Makes zero sense. It may not be a common problem but it is a problem nonetheless. Posting about it may help someone in the future.

Visually all the coils and seals looked great. Still, one spark plug well was completely flooded.

I acquired the car in 2011 with a CEL and replaced all spark plugs, plenum gaskets myself. No ignition issues until last week.

I know how a car should be. Unfortunately that does not equate to how Ford/Jag designed it. That's why this forum is full of useful tips and tricks how to fix and tweak things that the engineers screwed up. Oh, and I did find the problem and fix the car all on my own. Simply sharing what I found with others.

 

Cowl leak goes downwards. Not across magically into plug wells that in any case should be sealed. You're mixing up very different things.

What you're claiming makes about as much sense as saying a leak in the boot (trunk) allows water into the plug wells.

After 10+ years many things start to wear / age / degrade / etc and do not indicate design flaws.

If these cars had no age-related issues at 10+ years then they'd be a lot more costly to buy.

 

Well the water is definitely coming in past the cowl and straight into the cam covers. It's actually almost a straight shot down there, right past the silly plastic engine cover that is too short and does nothing to prevent the water coming in from the firewall side. I'll let you guess which coil failed, caused the misfire and had to be replaced

To make things worse, even though I only drove the car twice around the block with the misfire for diagnosis, the car just threw a brand new code P0430.... = destroyed catalytic converter in bank 2. Already ran OBD2 diagnostics and confirmed the cat is gone. I really am beginning to hate this car

 

Cats don't go bad from just a few misfires. How long was it doing it?

 

Just to clarify a bit, Ford did not design the S-Type, Jaguar did.

The rubber seal on the windscreen lower finisher is not designed to seal out water from entering the cowl. Have you removed the cowl and checked the drains to ensure they are not blocked by leaves and other debris?

From the photo of Bank2, it appears there is a significant amount of corrosion showing on the area from water having been present for some time.

 

Less than 10 minutes total. But it wasn't just a few misfires, it was consistently missing, initially only under load, after a few minutes even at idle. That's when I pulled into the garage, turned the car off and started looking. Then I started the engine a couple more times, first after taking out the O2 sensors (still misfired), then after I dried out the water (still misfired) then swapped coils (which moved the misfire). Then I ordered the coil and didn't start the engine until I replaced it. Then I reset all the OBD2 codes and all was good for ~50 miles ...then I got the P0430 which I never had before. Clear cause and effect.

 

13 yr old car and ONLY those few misfires damaged the cat(s) to cause that? No. You're fooling yourself if you think so.

 

Perhaps body and the interior...but the 3.0 V6 engine is Ford's Duratec, previously used in many Ford models including the Mondeo and Taurus.
https://en.wikipedia.org/wiki/Jaguar_S-Type#Powertrain

Most serious issues I've had with the car are engine related: exhaust/emissions and ignition. That's not to say that Jaguar didn't introduce more problems into the equation...but let's face it, the car has many parts designed and developed by Ford.

 

Who knows maybe they were already borderline but not bad enough to trigger a CEL on bank 2. Until now after the rainwater/misfire fiasco.

 

ill bet the cats were on there last legs and this issue just finished them off , any way onwards and upwards ! get them both done and reek the benefits of restored power,economy and efficiency . well worth changing both IMO . or the bank 1 will soon follow suet! probably long over due .

 

I bought my 06 3.0 and everything was wonderful until I drove through a 3-4" deep puddle too fast.. My car went into limp mode and was skipping on 3 cylinders. I changed all the coils and plugs and have been fine since.

 

Just came across your thread as I believe I'm experiencing the same water leak on my 3.0l.
Bought it just 2 weeks ago.
Ran fine until I gave it a good wash at home.

Started misfiring on cylinder 6.
I removed the engine cover and coils. Wells were full of water. More in 6. Of course i
panicked and thought it was a hg failure. But it didn't make sense.
Liquid was a slightly dirty colour not sweet or red. Plugs looked fine.

I will now have a look at the cowling as you mentioned. I know the previous owner didn't hand wash his car.

Thanks Chris