2002 S-type 4.0, 115K miles: Feel hesitations going uphill at constant or slight increase in speed. Downshift to 4th and it goes away. BUT, if I use cruise control, no hesitation whatsoever at constant or increase in speed. No other issues; no reduction in mpg. Your insights are appreciated.

 

intermittent misfiring coil(s) - also, when was the fuel filter last changed?

 

+1 on misfiring coils. The spark plugs should also be replaced at that number of miles if they have not been replaced recently.

Check the condition of the cam cover gasket and spark plug seals for signs of leakage as oil contamination into the spark plug wells can lead to shorted coils and misfiring.

 

Thanks for your response. Fuel filter changed at 80,000.

 

Thanks for your response. Next free day will do the plugs. Any suggestions on the type of plug to use - worth spending on iridium plugs?

 

Question - why would the symptoms to away when I use cruise control going uphill? If it's a misfire, wouldn't be evident with cruise?

 

Who knows but more likely coils than plugs. Do not use the wrong plugs or expect worse troubles.

 

You can download JTIS from this forum that has the information you need to correctly service the vehicle.

The owner's manual may also contain the specification for the spark plugs, or you can purchase plugs with the correct heat range from a local Jaguar agency.

 

Should really consider having the codes read at any big box auto parts store for free, then post the actual pending codes here.


Unless you have a blooming money tree in the back yard to start throwing money at guesses!

 

Thanks. Just checked with scanner and came up with pending PO303. Also, no check engine light. From reading some other comments, this seems to usually be the coil. Should be easy enough to replace and retest. What do you think?

 

Pull the #3 CP and switch it with another and see if the code jumps to that cylinder.
When pulling the COP, as mentioned above take a peek around for oil collecting in the spark plug well or on/around the COP boot.

 

Same issue here, keep me posted on a resolve? Tks!

 

Just to let you know that replacing the ignition coil on cylinder 3 (pending misfire on OBD-II) did the trick. Jag is purring again.

 

New coil on cylinder 3 did the trick. No oil noted around spark plug, nor old coil. Cover gasket was also in very good shape. Thanks for your input.

 

Replaced the coil on cylinder 3 and that did the trick. Thanks for your input.

 

Seemed to work for me too. But I noticed oil in the well. Great, another project.

 

You should have handled it when you replaced the COP. It is very easy to change out the cam cover and spark plug well seals when you have the plenum off.


Oh well live and learn.

 

Yea, it was all fine at the time I did the left side so I didn't. Thankfully I still have the right side gasket from the kit that included both. I was going to sell it, but it didn't! Whew. But as you say live an learn and it goes faster the 27th time around!