Heeeelp. 2003 disco 2 had o2 sensor no voltage. random misfire cyl1 cyl5 cyl7 replaced O2 Sensor with Bosch O/E seems that code stayed out so far.
cleared all codes but p0305 p0307 p0300 keep returning as she is missing like a B. new plugs wires coils Installed still same problem. did compression test 1,3,5 at 185psi 7 at 135psi. Note this vehicle has had a valve lifter rattle intermittently sometimes pretty loud for a while. She was running great then all of a sudden here I am. everything seems to be bank one

 

Do you have an UltraGauge or other scanner that will allow you to read fuel trims real-time? I once had an O2 sensor that was bad out of the box and although I got no codes directly related to the sensor I had misfire codes for all the right bank cylinders plus the bonus P0300 and DEFCON 5 P1300. Swapped the sensor for a replacement and the problems went away.

Note, however, that it took a drive of about 10 miles for the computer to bring the adaptive values or whatever they're called back into line. Even though there were no O2-specific codes the Bank 2 fuel trims were -25% indicating no signal or something like that. After changing the O2 the Bank 2 trims were initially in the -20s and gradually worked their way back to normal levels by the end of the 10-mile drive.

My clue was that all the misfires were on the same bank. The key components that each affect only one bank are the O2s. And as I said, I and others have reported O2s bad out of the box, even the Bosch 15175s. I'd try another if I were you and return the defective one.

 

Hi sorry about the delay and thanks for the info. I did change the O2 Sensor Bank 1 Sensor 1 OE Bosch. Same problem. I have borrowed a snap on modus scanner cleared all the codes and Bank one seems to be running lean. I have checked for vacuum leaks cant find any. I was wondering if my valve lifter issue could be the problem.? It seems to be rattling on bank one and the lower compression on 7. I'm wondering if I should go for the teardown as was suggested to me.

 

I'd suspect injector o-rings if you are seeing lean running.

 

Sounds like you need to go after fuel or vacuum leaks. You can also pull off a vacuum line and add some propane into it to force it rich. That way you can confirm that the o2 sensor is functioning.
Someone just had problems with misfiring on one bank and it turned out the injector harness wasn't plugged in all the way. Just a thought.

 

Ok guy's to update. did the cylinder heads. found bank one was leaking coolant at #7 position so both heads checked & machined. cleaned all the crap of the piston crowns Valve lifters replaced valves all reground. replaced all injector seals checked wiring & grounds. checked converter looks clear. found new O2 sensor out of range on max voltage. started her up misfiring #5 #7 ******

 

So after all that, it's still got misfires on two of the same cylinders? Is it overheating at all?

 

yeh i'm stumped checked voltage of new O2 sensor getting 0.010 volts? rest ok

 

No overheating in fact no valve lifter rattles either fuel system said open loop fault 1 2 but once rpm lifted at went into closed loop no more fault. this is the third bosch o2 sensor and its only reading 0.010 volts?

 

I would try forcing the o2 sensor rich. If you take off a vacuum line and put some propane in it, (or brake, carb cleaner) the o2 sensors should go full rich. If the sensor in question doesn't change from .010 volts, then it's either a wiring problem or an ECU issue. I seriously doubt you've gotten bad ones every time.