Hello. Looking to see if someone can provide some insight into this problem before I start throwing darts(money) at it.

I recently did the head gaskets on my 2004 Disco along with all the associated gaskets in the tear down. The plugs(NGK BKR6E-11 stock no. 2756) and wires(magnecor 8mm) only had about 20,000 miles on them so other than re-gapping the plugs to 1mm I left them alone. The front passenger side O2 sensor had about 4,300 miles on it so I left that alone as well. During the job I noticed that the RH(passenger side) exhaust manifold gasket to the head didnt quite line up with the front hole. I also broke off one of the 3 bolts on that same manifold going to the exhaust pipe. Not sure if either of those are related to the codes.

Once I got everything back together I drove it and immediately had leaking coolant burning, I could smell it. I looked under the hood and my two heater pipe clamps and my throttle body heater clamp were leaking. Coolant was all over the engine. Apparently I didnt tighten them enough and they havent leaked since. Again, not sure if any of this is related. Sometime either during or right after the leaking(cant remember) it started idling rough and felt a little weak and I got 12 DTCs. If I remember correctly(I have since cleared them) they were...

P0155
P1300
P0302
P0304
P0306
P0308

and 6 others I cant recall that are associated with the 4 even numbered cylinders.

To summarize the potential problem(s) is(are)...

1. A leaking exhaust manifold to exhaust pipe connection caused by 1 out of 3 missing bolts.
2. A leaking head to exhaust manifold gasket caused by a new but misaligned gasket(manufacturing error or wrong part).
3. Coolant got inside the O2 sensor plug.
4. Bad 20,000-mile-old O2 sensor.

I have the RAVE manual and couldnt find a troubleshooting walk through for these DTCs. My mechanics manual for my 2002 Civic gives walkthroughs for all the DTCs, things like checking voltages on the harnesses and such. Does RAVE not have a troubleshooting index?

Hoping someone with experience or Disco savvy can help me eliminate some of these potentials.

Thanks.

 

P0155 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
The other codes are misfires

If you replace a o2 sensor say sensor 1 upstream you should replace sensor 2 upstream at the same time.

Now the coolant you need to get that stopped if not done already. Dry out o2 connection and put dielectric grease in the connector and in the spark plug boots. Your rough idle is from all f the misfires you have going on possibly caused by the o2 sensor being wet.

Get any broken bolts out and put back together correctly to cure exhaust leaks the will eventually cause you more issues down the road.

 

In my siganture is link to the LR Bosch ECU manual, and it has voltage and ohms ranges for the O2s under various conditions and range of codes. Several pages attached for your review.

 

UPDATE: I checked the codes again after clearing them a few days ago. I got the following...

p1300
p0300
p0302
p0304
p0308

No more o2 sensor malfunction. Still cant figure out the misfires. Was getting a p0306(cylinder #6) at one point with the rest, now its just #2, #4 and #8. They are all on one bank, that should help you smart guys with a diagnosis.

@Savannah Buzz
Sweet! Thanks for the pdf!

@lr2001silver
I used dielectric grease on the spark plug boots when I put everything back together. Its been over two weeks since the coolant wet the engine bay. I would guess that it would be dried out by now, no? Could the exhaust leaks be causing these symptoms?

Should I try swapping the driver side for the passenger side o2 sensor to eliminate that possibility?

 

They're all on the even side so it could still be an O2 sensor especially since your first code was that sides sensors. Take a DMM and check resistance on both the harness and the sensor connectors. If one is a short/open then trace the wires to find a pinch or fray. I suppose you could swap sensors to see if the misfires follow the sensor but I'd test with a meter first.

 

UPDATE :

I cleared the codes, swapped the o2 sensor around, just because it was easy, and got all new codes...

p1300
p0304
p0308
p0300
p0130

I panicked.

Drove about 2 miles down the road. Cleared the codes. Drove 2 miles back to my house and wouldnt you know it. NO CODES!!! This was an even more pleasant surprise than what I expected, which is that I would get all these codes on the other bank of cylinders suspecting a bad o2 sensor.

My guess is that these codes are eventually going to show up on the driver side bank of cylinders when the computer realizes that I just put the bad o2 sensor on the OTHER side of the engine, but for now...WHEEEEE!!!!. No money spent!

 

It may take two cold start drive cycles for codes to appear again, don't do the happy dance just yet.

 

Ok, so I got the check engine light. Got the scanner out. Bad o2 sensor bank 1 sensor 1. It found me out. Thought I could pull a switch-a-roo and drive it for a while. Guess I have to replace it.

Like I said it isnt that old. 20,000 miles. Can I just use any cheaper-than-dirt sensor or is that why Im where Im at now?

 

No do not use a universal with no plug..... i think there was a post a few days ago saying and brand name is good just not universal Bosch is best since its a Bosch system.

 

OEM bosch plugs on amazon are less than $50, much cheaper than some other vehicles.