HI all. Hope all your Jags are running well. Mine is having a problem. It is a 1997 XJ6L. My CEL has been on for a long time. I checked it a month or so ago and got some code for an o2 sensor. It seemed to run fine, so I ignored it. Yesterday it felt like it was idling rough and then it stalled as I pulled into an intersection when the light turned green. I dropped it into neutral and restarted it and was able to get to my destination and back home again. This morning I pulled the codes and got 3. P0139, P0171, P1138. I am going to check for leaks as a first step later this morning but am looking for advice in case it is not obvious.

 

OK, I inspected the engine bay and there are no disconnected hoses or leaks which are making any noise. There is a rubber bellows-looking thing connected to the throttle which is torn up pretty bad. looking at info from this forum, it sounds like an o2 sensor related to cylinders 1,2 and 3 downstream may be the problem. I see 3 O2 sensors from the top, I am guessing these are "upstream" and the downstream are after the cats?

 

The 2 upstream are on the pipes above the cats and the 2 downstream are below them, a lot deeper. The codes indicate Bank 1 downstream sensor. It does sound like it is time for 4 new sensors. By now they are all tired.When replacing, do one at a time to avoid mixing up the connectors. They must be connected the same way they were removed.

P0171 System Too Lean could indicate an exhaust leak, namely at the manifolds, caused by cracks in them. Easy to check with the heat shield removed.

The rubber bellows is probably the small one on top for the cruise control. Connected by a rod to the throttle linkage. So your cruise control doesn't work?

DO make sure the large rubber bellows at the throttle air intake is free of cracks and seated well. A loose condition or a hole would allow unmetered air into the engine, potentially another source of lean, poor running.

 

Thank you very much for the reply. I did order one O2 sensor for now. As you say, the others are probably on the way out as well so, I will plan on replacing them as well. It looks to me like the cats are quite near the engine. The sensors just below, I can see from the top of the engine, are the downstream?
I have not had it on the highway for quite some time but, I think you are right that that is the damaged part. Should it be OK to leave it alone if I am not using it or, could it cause other problems?

Thanks again.

 

You're welcome!

Borrowing Parker's image here, you want to replace A (blue) which is near the bottom of the engine. If I recall correctly, it can be seen from the top, but not easily reached. Easier to do from under the car. The connector is behind the intake manifold up top, near the firewall and might also be tough to reach.



The broken CC rubber bulb won't hurt anything as long as you're sure it won't bind with the throttle movement. If in doubt it is easy to remove.

 

Thanks again Richard. That is extremely helpful.
Dan

 

Hi dbjags,

Just to supplement Richard's excellent guidance I am attaching the Diagnostic Trouble Code Summaries so you can look up the definitions and possible causes of codes.

Cheers,

Don

 

Thanks Don. I will keep this as a reference.
Dan

 

So, I ordered and received my 17mm sensor removal socket and, while it looks like it would work great, I cannot get it over the plug. There is a protrusion from the engine with a hole in it, maybe for bolting on some accessory, that is so close to the sensor, there is no way to get the socket over the plug. It is the bank 1 sensor 2. Has anyone come up with a way to do this?

 

If you're replacing oxygen sensors I suggest cutting off the cable as close to the sensor as possible, then either use special socket or normal one, or simply a ring spanner. I only have downstream sensors on my UK car and the inner sensor can be removed from underneath and outer one(visible from engine bay) from top with a normal socket, ~4 extensions and a breakers bar. For the upstream ones I suppose ring spanner might be best. If all fails(for whatever reason), you can always undo downpipes from underneath, literally 5 nuts and whole thing with oxygen sensors will come down. 50% chance on snapping manifold to downpipe bolts but they drill out easily.

 

Great advice. I'll give it a try.
Thanks.

 

Again, thanks for all the advice. I got it done but I had to improvise a bit. There was no way to get the special socket on the Bank 1 Sensor 2 due to the proximity to a transmission protrusion (image 1). I tried the spanner I had been using but ran it toward the left side of the car and got a long bar over it and, voila! it came off.
The next problem was I could not get the new sensor to thread into the pipe. Upon further inspection of the old sensor, I noticed that the threads were pretty much gone (image 2).
Here is where I had to improvise. I bought 5 hose clamps at Home Depot, 3 small and two large, put one small one on the new sensor with the two other small ones attached like dog ears. I then put the two large ones through the "dog ears" and tightened them to to the pipe. It has held up for over 100 miles so far with no codes and my gas mileage is now over 19mpg where i had been getting in the 14 range before.