My new NTK 25044s came today and I started to replace the upstream O2 sensors. I can see and touch the driver's side sensor connector below the coil pack, but it is on a bracket and the release lever appears to be on the bottom, and I can't see the Passenger side connector.

Is it best to remove the coil pack and if so are there any hints or photos somewhere so I don't screw it up? I looked in the RAVE, but it doesn't show the setup in my 98. Any advice will be appreciated.

There were some scraps of black plastic pieces around the connector that appear to be pieces of some plastic sheet under the intake plenum. Any idea what these are from?

 

OK, no replies yet, but using different search words in the archives I found most say remove the coil pack so I'll be trying that today.

I'd still like to know what the broken pieces of black thin plastic are from.

 

Yes, remove the coil pack. It will save you time and scraped hands/arms. It's held in with 4 studs/nuts. 10mm I think. Sometimes the nut will come off, sometimes the whole stud will come out. Make sure you have a stick magnet retriever for when the nuts fall.

 

i did this 1 time with coils on, never again, coils come off to easy, what your pic shows is drivers side o2 and it is clipped to a metal bracket on the bell housing, plus alot of oil leak crud from valley gasket

 

I couldn't get my fat hands between the coils and the firewall. +1 to what fish said.

 

I am sure that if the LR engineers had tried harder they could have made disconnecting the upstream O2 sensors even more difficult, but right now I can't think how. What a super PITA, but it is finally done after figuring out where the coil pack nuts were hidden under the wiring harness - all pointing up, fortunately. Mine had only 3 nuts on the bracket and two of them brought the studs out with them actually making it easier to wrangle the coil pack out.


Once out I see I may need to replace a coil as one had a blown out tower that I hadn't noticed when I replaced the plug wires. The inside cleaned up OK, though, so maybe a little JB Weld will fix it up for now.


I uploaded a pic of the connectors in case anyone else is contemplating this job. I remember reading that you will get really wierd results if the left and right O2 sensors are cross connected but it doesn't look to me like that would even be possible given the connector locations and the 18 inch leads on the sensors.

Now for the real fun underneath getting the old sensors out; hope my 17mm flare nut wrench holds out through two more. Oh, BTW I found more plastic pieces under the intake on top of that sheet metal pan. Maybe they are the remains of an under bonnet insulation if these trucks had one?

 

Yeah, had to use the magnet on a stick to get the nut/studs out and then to get my socket out when the big wiring cover pulled it off the extension. Even with the coil pack out it's a PITA to get the connectors off the brackets and then get them off the harness; don't know how anyone could get the passenger side off blind. I had to raise the bonnet as Tom suggested and lay on the engine trying not to break anything. I sure hope it will all be worth it in the end.

 

like i said i did it 1 time with coils in took hours and tore my arms up bad, since you are replacing them cut off the wires and use a box wrench on the sensor, i would also use some good heat or that freeze spray in a can on them, my drivers side stripped first time and i had to chase the threads what a nitemare

 

Fortunately my sensors came out easily once broken loose with a 17mm flare nut wrench and a dead blow mallet. The upstream bung threads were cleaner than the downstream ones had been, but I ran a 12X1.25 thread restorer in them anyway just to be sure. I used a 17mm stubby open end wrench to run the new sensors in about 5 flats past initial contact; I figured I couldn't overtighten them with the short wrench. Got the leads fished and reconnected and was ready to reinstall the coil pack that I patched with JB Weld last night.

I had planned to re-install the coil pack with bolts in place of the studs and nuts since I had some extras from the 95 D1 I stripped awhile back and two studs had come out with the nuts and I had removed the one on the passenger side that had not, but the tapped holes on the passenger side of the block were not deep enough for the bolts to tighten up so I put the passenger side studs back in with pliers and then found I couldn't lever the bracket up over the studs because the fuel rail stops it, so out they came again. My final solution was to flatten a few threads on one end of the studs with a ball peen hammer so the nut was hard to turn and then use the nut to turn the stud in through both the coil and fuel line brackets until it bottomed and the nut then turned on down to tighten it up. It helped to scotch tape the stud/nut to the socket to get it started. All this was done repeatedly climbing up and down a ladder and laying across the engine because the front end was still on the ramps I used to reach the O2 sensors. My calves got a good workout.

Got it all done and realized I had forgotten to disconnect the battery before I started, but she fired right up and both upstream O2 sensors were varying rapidly between .005 and .970 while B1S2 stayed above 1.0 and B2S2 stayed low around .015 to .025. Guess I may need to do the downstreams sensors also, but for now I'll see how it behaves and if the dreaded P1313 and P1314 return.