O2 sensors for 3.6 transplant

[Deadeye]

I have about 20 track hours (maybe 30 hrs on rebuild) now on my vario 3.6 transplanted into my '87 track car. Dropped the drive train to change the TO bearing and while it was out, I put in new spark plugs as I was not sure of run time on the old plugs. This was due to a somewhat rough idle . The engine idles very nicely when cold, but as it warms up it gets less smooth and drops to around 800 rpm. I noticed that the 4-6 plugs looked a little "damp" as compared to the nice dry light tan color of the 1-3 bank. This prompted me to check the part #'s on the O2 sensors that came with the engine which are not the same. One is a '95 part # and the other a '96 pre-cat sensor.

So to the point. Could the O2 sensor on the 4-6 bank be causing the fuel mix to be too rich on that side? Does the Motronic ECU differentiate between left & right cyl banks? Should I be using '96 O2 sensors as it is a '96 ECU? or should I use the '95 sensors as I am only using 2?

[Deadeye]

Crickets?

[Bill Verburg]

Originally Posted by Deadeye

I have about 20 track hours (maybe 30 hrs on rebuild) now on my vario 3.6 transplanted into my '87 track car. Dropped the drive train to change the TO bearing and while it was out, I put in new spark plugs as I was not sure of run time on the old plugs. This was due to a somewhat rough idle . The engine idles very nicely when cold, but as it warms up it gets less smooth and drops to around 800 rpm. I noticed that the 4-6 plugs looked a little "damp" as compared to the nice dry light tan color of the 1-3 bank. This prompted me to check the part #'s on the O2 sensors that came with the engine which are not the same. One is a '95 part # and the other a '96 pre-cat sensor.

So to the point. Could the O2 sensor on the 4-6 bank be causing the fuel mix to be too rich on that side? Does the Motronic ECU differentiate between left & right cyl banks? Should I be using '96 O2 sensors as it is a '96 ECU? or should I use the '95 sensors as I am only using 2?

A US '96 993 DME is OBD2 compliant and uses an 88pin harness

it does differentiate between left and right as well as pre and post cat. The cat does not have a mixing chamber as used in the '95s

AFAIK there is no difference between a '95 O sensor and a '96, just that a '95 uses one in the cat mixing chamber and that a '96 uses 2 precat, one L and one R and 2 post cat, again one L and one R, sensors. If you are not using the 993 central electronics then you don't care about the post cat sensors and you can discard them, the DME will be throwing codes like crazy but you don't care about that. The 2 precat sensors are used for any part throttle warm running, so you do care about them.

[Deadeye]

Bill, I had the stock ECU modified to eliminate the immoblizer and was told they altered it to ROW specs. Code reader shows no codes. Maybe I just have a bad sensor.

[Bill Verburg]

Originally Posted by Deadeye

Bill, I had the stock ECU modified to eliminate the immoblizer and was told they altered it to ROW specs. Code reader shows no codes. Maybe I just have a bad sensor.

I don't know how that could be done, I suppose that in their mind some changes were made so that the system, in some ways acts more like an OBD1 system

RoW n/a 993 use the same 55pin OBD1 compliant DME as US '95's, the 2 systems are in no way similar. There are some relatively minor differences between RoW and US 55 pin versions, for instance only the US versions monitor the SAI system

wrt O sensors, all the 55pin version use one O sensor, oe it is placed in the inlet mixing chamber of the cat. If the cat is eliminated a choice of L or R bank monitoring is usually made. The DME would have no way of knowing if the sensor was bad from monitoring the exhaust.

[wildcat077]

Bill,

On the subject of O2 sensors,i 'm in the finishing stages of my 95 3.6 install and was wondering about the O2 sensor situation ???
My engine basically came in boxes and i have to figure out where everything goes and the O2 sensor is one of my remaining puzzles.
I have a bung on both header pipes so left or right doesn't matter,it will go wherever it reaches the harness.
My question is do i only need one sensor ?

Cheers
Phil

[Bill Verburg]

Originally Posted by wildcat077

Bill,

On the subject of O2 sensors,i 'm in the finishing stages of my 95 3.6 install and was wondering about the O2 sensor situation ???
My engine basically came in boxes and i have to figure out where everything goes and the O2 sensor is one of my remaining puzzles.
I have a bung on both header pipes so left or right doesn't matter,it will go wherever it reaches the harness.
My question is do i only need one sensor ?

Cheers
Phil

Choose a side, doesn't matter which

thisis my old 964 engine