Okay so basically I have 135K on an 8 yr old s type that hates long trips. Ive always made it okay but not without a few error messages. I always get Restricted Performance and Gearbox faults towards the end of lets say a two hour ride. Ive also noticed decreased fuel economy at the end of the trip from the instant fuel meter. Any ideas why??? Short regular trips and Ive never gotten these error messages...

 

Read the codes

Also, has ALL the correct maintenance been done? Such as new plugs and the right ones? And any coils replaced with the proper ones? Etc.

You should have the opposite: these cars LOVE long trips.

 

I agree - these cars are great highway cruisers when they're in good shape from a routine maintenance perspective. That's the primary reason I purchased our S-Type. My wife drives it solo from Raleigh to Tampa and back to visit her elderly parents 6 to 8 times a year. She leaves again this coming Monday. This will be the first time with the new Dunlop tires, so it will be interesting to see if her long-distance mpg goes up or down....

 

I agree - those cats love long trips - did few and never had any issues..The longest one from Chicago to Cape Breton...It had great time in Cape Breton..

 

I agree these cars are great highway cruisers... As far as the plugs and coils, I took it to the jag dealership over the summer and replaced half the coils and plugs. (all 4 coils+plugs on the passenger side bc thats what the jag dealer said) plus a new intake manifold gasket...oil and all fluids were good before the trips...

 

When were the other 4 plugs done? Other coils - ever?

But read the codes

Any other issues? Electrical? Bad starting? Odd noises? (Ignore the tie rods here.)

 

all routine maintenance has been done while ive owned the car and it was serviced well also from previous owners. the coils and plugs were the correct replacements too. The gearbox fault could be anything but the restricted performance really gets me... if i restart the car the errors go away and i wont get the restricted performance msg until maybe after 30 mins have passed

 

Usually there will be codes stored. Those are hints to the problem(s). On these cars it's very rarely the gearbox. But, the gearbox won't like the effects of the actual problem(s) and then you get the box adding its unhappiness. RP is another outcome. It's the car defending itself, trying to avoid bad damage. So... codes? AutoZone/PEP - free.

If you're lucky the actual problem(s) won't have caused something more serious - yet.

 

no electrical issues or bad starting. I should just replace the other four coils and plugs but then again im going by the jag dealer's diagnosis and i did exactly what they told me to do. ive read the codes too but theyre the same codes from before the repairs...

 

So what are they?

I wonder if they managed to get them crossed over side-to-side......

Then clear them and see which one(s) occur first.

 

ive gotten two misfires in the past year and one 5-6 shift error code

 

cylinder misfires in 4 and 6 i believe which means there are on the same side...the drivers side. and jaguar didnt tell me to replace those...but is that the cause of the RP???

 

They could easily be the cause. Misfires mean lots of bad things, including that the gearbox feels jerks and can be upset.

Misfires also mean unburnt fuel going into the cat (as well as the upstream O2 sensor). Risk of further damage.

At that mileage I think I'd put in 2 new coils and 1 or 2 new plugs (probably 2), for those cyls. But for sure I'd have a really GOOD look at the coils, plug wells and the plugs - looking for oil/water/dirt/anything. (I always keep small old parts "just in case" but it's not everyone's idea of what to do.)

I'd get a cheap OBD tool like an elm327 and check the fuel trims too. Parked. At idle and at 2500rpm. But I'd do the coils etc first if I didn't already have the tool.

I don't get it - why didn't they say to change anything for cyls 4 & 6?

 

I have no idea why the jag techs didnt tell me to replace those too. how long do s type coils last anyway? also the RP didnt make my engine feel any weaker, it felt the same as always. my battery is new too. thanks for your help jagv8, I really appreciate it.

 

At that many miles I would do a transmission filter and fluid change. As you know without a dipstick we are in the dark as to proper fill level. We have a great place to get the proper parts and fluid now so it's not the battle it use to be.

It's up to you but I consider coils and spark plugs as wear items. I would for sure replace the other 4 coils and plugs. Jagv8 brings up a good point to check for oil in the spark plug wells. This was not too common but with advancing age we are seeing more cam cover/plug well seals leaking on the V-8's. Before the V-6 cars suffered much more from this.

The restricted performance might be related to moisture in the throttle body connections. This is known problem and can be from a seal leaking at the windshield wiper pivot point. This drips water directly on top of the engine. Might be worth a check by carefully playing with a water hose and see if there any leaks?

Does rain seem to make any difference to the car going into RP?
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no rain does not make any difference that I know of. However, my plugs were kinda oily when I replaced them!

 

North of Dallas, Texas to Orlando, Florida. Thats the longest I traveled on my STR without a hiccup Definitely give her a nice tune-up and a fresh batch of Tranny & Differential fluid and you'll be set.