So the XJR threw a check engine light today... Codes P0301, P1138, P1158. It still runs nice and smooth and has the same fuel economy. It does have a slightly lumpy idle when stopped and in gear, but it was that way when I bought it.
Oh, I did install new Champion RC9YC plugs when I did the timing chain tensioner replacement.
You guys have any ideas as to what it could be?

 

Faulty coil pack and bad oxygen sensor bank 2.

 

Hi Type_Rated,

Welcome to the Jaguar Forums! Sorry to hear your Jag is having issues.

You can download the X300 Diagnostic Trouble Code (DTC) Summaries manual from this forum at the following link:

http://www.mediafire.com/download/q2...6_ECM96_97.pdf


Your P0301 code indicates a misfire in cylinder 1, which is the one at the front of the engine closest to the radiator. A simple test is to swap the cylinder 1 ignition coil with the one for cylinder 2, clear your DTCs, then see if P0302 appears, indicating that the misfire has moved to cylinder 2. If so, a bad coil is indicated. If not, further diagnostics will be required per the DTC Summaries manual.

The manual will also give you diagnostic suggestions for your O2 sensor codes.

Cheers,

Don

 

Thanks guys!
Based on what I've read, both O2s are showing a rich condition, which I would say would be more likely caused by incomplete combustion in the misfiring cylinder rather than both O2s failing at the same time.
I'm going to go ahead and replace the faulty coil pack. I'm assuming since the car still runs pretty smooth, the coil is just getting weak and hasn't completely died.
Any recommendations on where to get a quality replacement (other than the dealer)? I've heard some hit or miss things about replacement coil packs.

 

Type rated:
You have made a common mistake;
The lambda sensors are OXYGEN sensors, not combustible sensors. So a misfire causes a lean measurement since the mixture is not burned and excess oxygen is still present.
Yep- check it out in the literature!