I have a 2006 S Type 3.0 V6 with 88,000 miles on it. Recently had the coils replaced due to 2 of them failing. A few weeks later the car began to stumble, miss fire under forced or full throttle on the highway roads. It goes into "low performance mode" with a check engine light. If you turn the car off and re-start after a few minutes it will be fine. Runs fine around town. Took it back to the mechanic and put the scan tool on it. It shows no codes so he says its fine, but its not. Called the Jaguar dealer today to take it to them. I was told they don't work on the older Jags as they don't have the tools or software to do the work.
Any ides as to what the problem is?

 

Hi There,
Have you searched on this site for s Types with similar symptoms?
I recall seeing at least one thread describing this problem.
You should also check the Sticky section.
Not having experienced this problem this is all I can do.
Cheers and Good Luck,
Cubist

 

Yes, I searched for similar problems and nothing really came up.

 

Check the fuel trims.

Also make sure it's running CL (closed loop) on both banks.

 

Were you getting the "Low Performance Mode" and CEL before the coils were replaced? What symptoms did you previously have, from when you mentioned two of the coils were failing? If you're getting new symptoms after replacing the coils for a different reason, that would make me think your new coils are the problem. Don't fall into the trap of thinking something can't be bad because it's new. I've have plenty of new parts bad from stock.

Also, where did you get the coils? Some Chinese eBay specials are of suspect quality.

As JagV8 suggested, check the fuel trims, too. Details here, courtesy of Gus:


JagRepair.com - Jaguar Repair Information Resource

 

This is a problem that can be solved. Its not a huge deal but w/some tools and time it can be figured out.

What you describe sounds like weak ignition.
As the load on an engine increase you need MORE of the 3 basic elements to make fire. More air, more fuel, and more (stronger) spark. Since you changed coils its seem intuitive that they might be bad. However those coils are depending on an underlying fundamental of sufficient power and ground for them to to their job.

1.- Check battery cable connections at both ends. On the battery and on the engine. Check all connections related to ignition and starter. (remove, wire brush both parts, and re-assemble)
- This is a step on an older car that doesn't hurt anything, its free, and helps rule out unseen problems.
- Check battery voltage w/engine off and idling. (Jags seem to be overly sensitive about lower voltage)
2. If no change / not solved.. Get a scanner that shows fuel trims and you can see if the engine ECU is trying to add or remove excessive amounts of fuel during those times. I have several scanners but one that works well is OBDLink MX. It has its own app and also works with other apps like TORQUE. If you want to go cheap... you could probably do this for under $20 (I like higher quality tools and don't skimp on them)
I'd look at the fuel trims and also look at voltage during the time of missing.
3. If grounds are clean, battery voltage is ok, and fuel trims are not more than about 5% out of whack... I'd then suspect the coils or something sending a wrong signal to the ECU. Like a bad crank or cam sensor, or maybe a MAF sensor.

Don't worry about the unknown. Just methodically step through the basics and you'll figure it out.