I have a 2003 Discovery HSE with 125,000 miles
Bought the Rover about 6 months ago
Service Engine light came on 2 months ago
Car had a Rough idle and exhaust smelled rich
Code P0150 at first then P1174, P1170, P0300
I replaced air filter with paper filter,
Bosch double platinum plugs,
Front RH O2 sensor,
Did oil change,
Added seafoam to gas

Then cleared codes and light stayed off for a few weeks
Now P0150 came back and P0308
Checked cylinder 8 and plug was gapped at .05
I re gapped it at .04 and seafoamed the throttle body
with aerosol can. Disconnected battery to reset the light.
Rough idle went away but light is back on.
Any suggestions would be greatly appreciated!!
I'm thinking fuel injector or MAF sensor.

 

Any coolant loss? Rear cylinders seem to love to have leaky head gaskets....

 

I haven't noticed any coolant loss. But there is a lil oil on #8 spark plug and plug wire.

 

Oil and O2 connectors is usually a bad combination. This time of night you can go out and let it idle in total darkness and look for arcs where insulation is breaking down (boot, plugs, wires, coil).

 

Ok I will check it out tomorrow bc im about to pass out for the Night. But the front RH O2 orange connectors did have oil on them and I sprayed them with electronic cleaner. They cleaned up real nice but P0150 came back. I did that today actually. There's definitely an oil leak that I need to find and fix before everything I replaced recently gets covered in it. But I been reading a lot about fuel injectors causing the P0150 and other misfires on the D2. Where is DiscoMike the master! I see that guy all over Rover Forums pin pointing issues. Any help is much appreciated though. Thanks Savannah Buzz for the fast response and tips!

 

You said you cleaned the connectors. Did yo have them disconnected when cleaned, Did you use die electric afterwards? I would suggest doing an engine bay de greasing. It will help in finding the leak. Def, look out for coolant dissapearing. as Savanah says those rear cylinders like coolant. Before you go looking at fule injectors you need to go simple first. It could be as simple as a dirty connector, a loose wire. Also there is no need to Gap those plugs. I had a re-occuring p0150 and I had replaced the upstream sensors as well. I took the connectors apart cleaned them and applied die electric and no more codes. You should consider replacing the plug wires with the upgraded 8mm as well.
For the oil leak, in the short run get a bottle of white shepherd and give that a go. but still do an engine clean. keep us posted.

 

First, you don't drive for 2 months with a check engine light on, STUPID thing to do.
Second, always replace the front 02's in pairs.
Have you replaced your old wires with 8 mm silicone plug wires?

 

Mike I have the Grey plug wires and they look clean. Are those the original ones? Do you think replacing those will fix this issue? Also will die electric help those O2 connections at this point? I'm financially strapped right now so I'm trying to buy parts that will address the current issue. If I currently had enough money I would buy another o2 sensor or whatever else needed. And I have barely been driving the Rover the last 2 months bc of the service engine light and have been trying everything I can to fix the issue not ignoring it. Thanks man.

 

Alright I replaced the other front 02 sensor and got some 8mm magnicore plug wires. Sprayed the O2 connectors with die electric. Reset codes and Truck runs like a champ but service engine soon light started flashing which I never noticed before. 1 Code and of course p0150. I've checked for intake leaks with carb cleaner and no change in idle. What else should I check, clean, or replace now? Could it be the fuel injectors?

 

0150 is a code for front O2 sensor short circuit or voltage below .0399 volts. If reset it may take two drive cycles to pop back up.

You can leaqrn more about how the code is generated by downloading the Bosch ECU manual - https://www.cubby.com/pl/LR3+worksho...uter%20Manuals