I came to a stop at a traffic light and noticed that the idle on my LR3 seemed a little rough. When I accelerated away from the traffic light, the engine felt like it was missing on a cylinder and I got a message on the dash: Reduced engine performance. Shortly after that I got a check engine light. I limped home, a short drive away. For the record, "reduced" is an understatement. I was in the middle of moving from one house to another and decided to let the dealer, well, deal with it. I didn't want to just hand it over to them blindly so I decided to check codes first.

I used an IIDTool to pull the codes (misfires on cylinders 5 & 4) and then cleared everything to see if they'd come back. Wishful thinking: same behavior. I thought about it and decided that the likely culprit in getting 2 misfires at once was something electrical. I mean, what are the odds of 2 valves or injectors on different banks going bad simultaneously? I figured a coil pack was likely and decided to try swapping cylinders 5 & 7 to see if one of the misfires moved from 5 to 7. The number 5 misfire DID jump to number 7 but the number 4 misfire jumped to number 6. Odd. I figured that whatever was wrong with the bad coil pack, now on cylinder 7, must be inducing a current or otherwise screwing with nearby wiring, causing the other misfire.

When the service writer asked, "What seems to be the problem?" I was able to say, "I am pretty sure that the coil pack on cylinder number 7 is bad." I provided detailed background and he thought it likely that was it. After a modest repair bill and a short dealer visit, I was back in business.

I wanted to share this story in case it helps anyone else with multiple misfires showing up at once. For those wondering why I didn't just replace the coil pack myself, the dealer didn't have any in stock and I needed a working vehicle since I was moving. The dealer gave me a nearly-new Evoque as a loaner (500 miles on the odometer) so it worked out great for me and I was happy to pay Land Rover to fix my problem. I was VERY happy to get my LR3 back.

 

I have had the same problem the past few days. I have a 2007 LR3 with about 158k miles, spark plugs replaced about 40k miles ago, and one cat converter replaced about the same time. Its had an intermittent CEL come on, but the other day it just all of a sudden started idling rough. A few minutes later the CEL started blinking and the message "Reduced Engine Performance" popped up. After checking the forums, I checked my air filter, cleaned the MAF sensor, replaced the capacitor, and cleaned the throttle body. After doing all of that yesterday, it seemed to be running fine. But after driving almost an hour around town, the rough idle returned. Today the rough idle continued, but after the engine warmed up. I have not had the codes read, but I'll probably do that tomorrow at my local AutoZone. Now after reading SoCal's experience I am wondering if it's one or more of the coil packs. Other possibilities I've considered is the other cat converter or the O2 sensors. Anybody have other explanations?