I've had my new 2004 discovery S with 100k miles for about a month now, and on my weekly commute on the parkway, my car began to misfire. P303 p301 p305. It also came up with a leak bank code and o2 sensor inactivity codes, along with the p1412 and p1415 codes which won't seem to go away. I replaced the spark plugs, fluids, o2 sensors, and alternator so far, fun month for me XD. I just want to clear these codes so I can pass inspection, any idea if these codes are linked? Should I just replace wires/coil then address SAI codes, or maybe the SAI is causing all of this? New to this car having trouble diagnosing this....

 

I can't help with the SAI codes, but all the misfires on odd-numbered cylinders point to a problem with the upstream O2 sensor on the left-hand side.

I know you say you already changed the O2s, but they can be finicky. I've chased O2 gremlins more than once. How long did the truck run well with the new O2s before the misfires appeared?

The first thing I'd do is double check the O2 connector for any sign of oil contamination. Disconnect and reconnect it. If that doesn't work I'd return the sensor to where you bought it and exchange it for a new one. Bosch 15175 sensors have been known to be bad out of the box, including for me a couple of times. Others have reported good results with the Walker brand O2s. Good luck.

 

it idles rough sometimes in park. I'll have to check which o2 sensors I got. There was a wire getting sprayed with oil around the back of the engine, I tried to cover it up with heat tape. Could that be the o2 sensor wires?

 

The sensors are trying to tell you something is wrong.
Since this is a new vehicle to you, do a compression check. Start with confirming the basic health of the engine. I can give you instructions if needed. Depending on the results, we can proceed from there.

 

k I'll do a compression test. My mechanic seems to be under the impression it's the coil pack. We recently did the head gasket as well, no coolant loss now, so is it worth it to bother with the compression test?

 

It looks like lean bank 1, I would check injectors and o-rings. I have heard coils rarely go bad, though they are replaced often. I haven't replaced mine, but I did put 8mm Magnacor wires on, and flushed/backflushed each injector and put new o-rings on at 80k. I flushed the injectors myself with a car battery, remote start switch, piece of clear tubing, and Seafoam green. I brought the weak ones back to good doing this. My injectors are original. I will re-flush them again when I do my head gasket, and replace them if needed.

 

Your first codes are all related to cylinders from one side of the engine, so you ignition coils may be going. they do go bad. I had the misfires your speak about and it was cleared up with coil replacement. Your other codes are related to your SAI and could be your Idle Air Control valve. It can be taken off and cleaned with brake cleaner.
The lean bank code may not be as radical as Lisa suggests. It could be that the MAF is going, a vacuum line is loose(also could be why you are getting SAI codes) or the hose clamps from MAF to intake are not tight enough. Also you must make totally sure the connections of you O2's are fully seated.

 

I figured it would be more helpful to show the codes than explain my issue, so I retrieved the codes. 6 confirmed and 7 pending.

Hopefully this helps. I just redid o2 sensors and spark plugs a week ago, inspection sticker needed soon lol, trying to get it through before more problems come.

 

While you have new plugs, i would suggest to have a complete tune up including wires and coils. With regards to the sai, listen to the pump when you start up if its working. It helps warm up your sensors upon start up. Also check the filter canuster beside it, might be full of dust. Just remive filter and vacuum It.

 

Finished the coils and wires, now 2 4 and 8 are misfiring. Not sure where to go from here... Still same sai codes as well, along with the one mean bank...