I'd like to share a recent engine issue that can be worth having here for future search reference. Mine is a 6, so not so sure how much this may apply to a V12; got feeling, probably the same.

No.1
For a few months I have been noticing that when I drive the car from a cold start, it feels "normal" as in quick with nice torque response, but once it is warmed up it's not the same, like it loses pep. This has been even more noticeable recently.

No.2
After driving for a while, whenever I stop at a light, I've noticed the AFR gauge (wideband) creeping up (i.e. leaner), to the point that idle starts to become erraric. Typically, it took about an hour driving the car for this to happen.

No3
About a week ago, I was coming back from a car show (freeway drive) and closer to home, when I came to surface streets and stopped at a red light, the idle became so erratic that I had to put it in neutral and give it extra gas for the duration of the light so it woulddn't die. Meanwhile, I noticed something new: the AFR began to creep down -for a change- as in getting richer and richer and, finally, a code was displayed, FF-44 which relates directly to an O2 sensor issue.

After a careful leak test of the intake and exhaust with no trouble found, I changed the O2 sensor and all, No.1, No.2 and No.3 problems went away, just like that. I went out for a drive and after the car was driven for a while, it felt as powerful as when it was warming up. I went back to my driveway, kept the engine running and waited for a good while for something to happen to my idle/AFR gauge. Well, nothing happened, other than the normal stoichiometric swing between 14.3 and 15.2 AFR.

The fact that all the problems went away, confirms that the O2 sensor can create, not only a rough idle, or even stalling, but that weird cold/hot power disparity, as well. Various related Internet sites that I checked only give a list of possible problems, take your pick. The worst I found are those forums entries (of various car brands) where people shoot out all kinds of stupid, unrelated or right down ignorant responses, kind of "giving their opinion" without paying any attention to what the problem is in the first place.

BTW, it's so great to have that trip computer there, with related codes displays, that I thought why in the world didn't they keep it there for '95 and '96? Plus, I love having that wideband AFR gauge for reference. It tells you immediately when the cooking starts going awry. Perhaps, I should've done something earlier, when it was telling me that there was something wrong with the AFR at idle.

I hope this post helps somebody having similar engine behavior.

Cheers,

Reinaldo

 

Interesting.

Can you tell us what kind of O2 sensor you put in? I know the OEM costs a kings ransom, from Denso, but there seems to be tons of (much cheaper) options.

Thanks.

 

First, I went to the Internet and found prices from $25 and up to $110.
All the ones that looked like my OEM unit, which is a 2-pin connector plus a separate (and rubber booted) single spade terminal went from about $65 and up. Some of the cheaper ones come with non-terminated leads that you need to re-terminate yourself. Most of the more expensive ones appeared to be Bosch. Then I called the local dealer and their price was in the mid $100's, plus they still had to order it. One of the reasons to go with the terminated wires is that I just learned that when these sensors compare the exhaust gasses vs. the atmosphere reference, they get the latter via the wires, themselves, meaning via air wicking through the wires, of all things and I thought that the wrong termination (or solder job?) will carry the risk of obstructing the access to the atmospheric reference. Man, was that a new one...

At the local auto parts they had the Bosch unit, P/N 13313 at their warehouse for next day delivery. Wasn't cheap at $92.99 with "Lifetime limited warranty". Not interested in going through the weekend and part of next week waiting, I just got the Bosch unit and got it over with.

Tips, should you need to do this job:
Neither the removal, nor the installation were a walk in the park. The pipe after the forward dual catalysts runs inside a sort of a tunnel under the floor and the sensor is installed, as it should, on the top side, for a vertical orientation. This gave no access to a wrench (spanner) and gave only one click to turn my rachet (provided that it wasn't resting in the middle...), where I had that "special" 7/8 socket that has a slit on the side to pass the sensor leads. Then is when the real fun started; the thing just wouldn't budge, totally frozen to the bung with no room for a good grip/turn and no access for a piece of pipe to increase the arm. So, before going into applying heat or to run the engine until warm enough (rules kind of change when things are pretty hot down there) I got me a far better tool from the auto parts ($30) that has a longer and curving arm that can clear the tunnel giving access to increase the arm with a pipe and, boy, did l let it have it. Then, it took some 375 tries to get the darn thread started with the new sensor, changing position of my body like 360 degrees around.

But, all that struggle soon fizzled away when I discovered that all the issues were gone and, finally, with a very smooth running engine.

Cheers,

Reinaldo

 

Reinaldo,

Thanks for the info on the Bosch p/n. My sensor is ok at the mo but you never know!!

I think the sensor is different for our MY compared to the 95 or 96. Also we use just one sensor and I believe the later cars need 4? As Vee said they can be pricey!!

Cheers,

Allan

 

You're correct, Allan.
The '95 - '96 AJ16 engine uses four Oxygen sensors, two in front of the catalysts and two after, and all 4 feature a new 4-pin configuration vs. the 3-pin conf. on our AJ6 engines' single sensor. The 4th lead is a new reference from the ECM. All four of these leads are conveniently integrated into a 4-pin connector.

So, no, that Bosch unit does not work with the AJ16 system. There are plenty in the Web at about $30 to $40 more than I paid for my Bosch unit.

Cheers,

Reinaldo

 

The V12 use a single sensor for each cylinder bank, and not wideband. I "think" all years use a heated version but I may be wrong for early US models.

 

Just to clarify, of course that no stock O2 sensor is wideband. I do have a wideband sensor, but it is a special sensor that came with the AEM indicating system, which includes a special harness and the cockpit gauge.

I wonder if the V12 sensors are the same as the AJ6 engine sensor.

Cheers,

Reinaldo