Replace O2 Sensors, Now Misfire on 3 and 7

BarrettRC8

Member
Jul 31, 2017
14
0
San Diego
This afternoon after receiving my new O2 sensors from Atlantic British, I decided to resolve the poor gas mileage and Check Engine Light that I had, through research, deduced to be the cause of the problem (Truck was giving a P0147 code).

Now, after about an hour and a half, I had the new sensors installed - What a pain getting your hands into such a small spot! Unfortunately, after starting the car, and clearing the Check Engine Light with my Ultraguage and allowing my Discovery to run for a bit, I was presented with a P0300, P0303, and P0307 light - Multiple Misfires, Misfire on 3, and Misfire on 7. I have never seen any of these codes prior to the installation of the new O2 upstream sensors. Any idea what it could be?

If it helps at all, the American passenger side (starboard for you sailors) old O2 sensor was completely black with soot. I popped the hood and could see smoke emanating from that replaced O2 sensor.

And while I'm here, I topped off my coolant about a week ago with Prestone 50/50 and my truck, which was running routinely between 191 and 194* F now will peak at up to 210, averaging 203-206 unless I have the heater running.
 

BarrettRC8

Member
Jul 31, 2017
14
0
San Diego
This afternoon after receiving my new O2 sensors from Atlantic British, I decided to resolve the poor gas mileage and Check Engine Light that I had, through research, deduced to be the cause of the problem (Truck was giving a P0147 code).

Now, after about an hour and a half, I had the new sensors installed - What a pain getting your hands into such a small spot! Unfortunately, after starting the car, and clearing the Check Engine Light with my Ultraguage and allowing my Discovery to run for a bit, I was presented with a P0300, P0303, and P0307 light - Multiple Misfires, Misfire on 3, and Misfire on 7. I have never seen any of these codes prior to the installation of the new O2 upstream sensors. Any idea what it could be?

If it helps at all, the American passenger side (starboard for you sailors) old O2 sensor was completely black with soot. I popped the hood and could see smoke emanating from that replaced O2 sensor.

And while I'm here, I topped off my coolant about a week ago with Prestone 50/50 and my truck, which was running routinely between 191 and 194* F now will peak at up to 210, averaging 203-206 unless I have the heater running.
2003 Land Rover Discovery 2 with a 2" lift, 32 inch tires, and 76,000 miles.
 

Swedjen2

Well-known member
Sep 12, 2018
142
11
California
You probably have the stock thermostat which is a light cream or grey color. Lucky8 has 180 degree thermostats for 85, they are black.
 

BarrettRC8

Member
Jul 31, 2017
14
0
San Diego
Ok, so I’ve driven the car several times now. Temps have stabled out around 190-198 and no more misfire pending codes. Now I’m getting a P1415 - Secondary Air System Fault Bank 1.