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2001 XJ8 Jaguar

Pleasssssse help me. I have a 2001 XJ8 Jaguar that I purchased new. I’ve never had ANY problems–love my car–I have 95,000 miles on it. Recently, on a trip to Louisiana and Texas with my 87-year old Mother, I needed gas. However, the station (in the middle of no where) was out of Premium so I had to purchase a middle grade. (My husband told me this would be o.k. for one time!) The next day while traveling across south Louisana, a computer message came on–“performance restricted.” I looked it up in the book and the Britsh informed me to “limp home”. I was about 600 miles from home, so it took a while–limping. However, by the time I got to New Orleans the message went off. I traveled on home to my home in Mississippi and have since filled the tank numerous times with Premium gas. I carried the car into the only shop in our home town that has the infamous computer and they hooked it up and reset the computer. The message refered to a “knock” detected. I told the guy the story and he said, oh yeah. For two days–no message–thought the problem was solved–then the amber engine light comes back on and now the message “restricted performance” is back. This morning I filled up with premium and both the light and the message went away.

What’s the deal? Do I need to “limp” to the dealership–a hundred miles away? The car runs great–but the message and lights make me nervous about being on the road.

Please help this Southern belle!

95K trouble-free miles in an XK-8. That’s marvelous!

Using a lower grade of gas will allow engine knocking. The computer detects this and adjusts the ignition timing to compensate for the lower octane. The adjusted timing reduces the performance of the engine, hence the light.

You don’t need to “limp.” You can drive the car normally. I would keep filling with premium and see what happens. If the light stays off don’t worry about it.

If the light stays on for several days and won’t go off there may be another problem. LOTS of things will cause the light to come on, and at 95K miles a sensor or two could be nearing the end of their lives. Only a computer scan can tell you why the light is on. You can’t assume it’s the same thing every time.

Thanks for your response; I plan to get the old girl hooked up Monday.

You can get the ECM codes scanned at a local chain auto parts store. Well, maybe; I don’t know the stores in Mississippi. But call a local parts chain and see if they have an OBD-2 scanner for loan. It won’t cost anything. They will give you the scanner and you will follow the directions and collect the codes. They will read the codes, tell you what they are and help you interpret them. I use Advance Auto Parts here. They are owned by Sears and my be near you, too. Once you have the codes, stop back and we’ll help you figure out what to look at.

Just got back from the shop. The code is 328 Knock Sensor High Bank 1. The mechanic said the sensor is bad and will eventually need to be replaced. He reset it and the amber engine light and the message RESTRICTED PERFORMANCE are off. With 93,000 (I checked the odometer), how much does it cost to replace a sensor?
Thanks

Most knock sensors are not too difficult to access, there are a few that are deep in the engine. Don’t know about Jags. It should be easy to get estimates for the job.

The part is about $100. Here’s a description of the location. It sounds like some disassembly is required. The labor is probably several hundred dollars.

http://www.fixya.com/cars/t1268878-knock_sensor_location