Catalyzer temp sensor on 75 280Z

[Serban]

Hey everyone,

 

I tried searching for this several different ways, and wasn't able to come up with anything relevant. I've got a 75 CA 280Z which came with a cat, as well as the catalyzer temp sensor. I recently took the cat off (original one, yikes), but have not welded a bung in the current piping to reuse the temp sensor. 

 

Is this sensor truly required, and does it act anything like an O2 sensor? I'm really curious if this is causing the high fuel consumption, or if it's something else.

 

Current setup is a stock L28 with a custom made top feed fuel rail with Ford 19lb injectors. The car runs fine, but after 75 miles, it's down half a tank! I plan on putting my wideband gauge on the car this weekend, I am curious how rich this car runs. I'll weld in a bung for the catalyzer temp sensor as well. Hopefully that may fix the problem?

 

I've only had the car for about 2 months, and this is the first time I've driven long enough to see fuel consumption. So I don't know if it's had this problem previously, or something I've created once changing the fuel system.

 

PS, I've also eliminated some of the items from the intake manifold. BCCD is unplugged, EGR removed, air regulator removed. I live in South Florida, and it never really gets too cold down here. I know most of these components are for cold starting and help out with cars in cooler climates.

 

 

Edited December 20, 2013 by Serban

[dexter72]

What is the CC rating of those 19lb  injectors??...They may be to big for the setup your running, Also are they high or low impedence injectors??....

[NewZed]

Current setup is a stock L28 with a custom made top feed fuel rail with Ford 19lb injectors. The car runs fine, but after 75 miles, it's down half a tank! I plan on putting my wideband gauge on the car this weekend, I am curious how rich this car runs. I'll weld in a bung for the catalyzer temp sensor as well.

Those injectors are in the ballpark.  Stock is 188 cc/min (17.9 lb/hr).  6% too much fuel.  1975 doesn't have a "catalyzer temp sensor", but it does have a floor temperature sensor.  It's only function is to tell the driver what is causing that smell,so that they can have their converter checked.  1975 didn't use an O2 sensor for engine management, so if you had an O2 sensor installed, it was added later.  Finally, 75 miles on a half tank could just be a bad fuel level gauge.  You might be worrying about nothing.  Getting real numbers will make you feel more secure.

Edited December 20, 2013 by NewZed

[Serban]

What is the CC rating of those 19lb  injectors??...They may be to big for the setup your running, Also are they high or low impedence injectors??....

These are high impedance injectors. I was told I can use them without any problems. Its going from high impedance to low impedance where you'd need resistors.

 

 

Those injectors are in the ballpark.  Stock is 188 cc/min (17.9 lb/hr).  6% too much fuel.  1975 doesn't have a "catalyzer temp sensor", but it does have a floor temperature sensor.  It's only function is to tell the driver what is causing that smell,so that they can have their converter checked.  1975 didn't use an O2 sensor for engine management, so if you had an O2 sensor installed, it was added later.  Finally, 75 miles on a half tank could just be a bad fuel level gauge.  You might be worrying about nothing.  Getting real numbers will make you feel more secure.

A 6% increase shouldn't be this bad though? I imagine it would run a little rich though. My car is a California 280Z, and it did come with a cat and that sensor, which the FSM calls a "catalyzer temperature sensor". Isn't the floor temp sensor in the trunk just above the muffler?

 

Here's what the sensor I took out of the cat looks like. I wasn't sure if it was an O2 sensor or not.

 

I'll top off the tank to see what kind of mpgs I'm getting.

 

Here's the location of the sensor from the FSM.

Edited December 20, 2013 by Serban

[NewZed]

You missed my point on the fuel mileage (but got it at the end of your post).  You don't really know what it is, you're just assuming based on the gauge needle moving a small amount, and the odometer number changing.  And who knows if the odometer reads right.

 

Post a page number or a picture of the FSM's reference to a catalyzer temperature sensor (the Nissan Factory Service manual, not a Chilton or Haynes book).  I've never seen the sensor so don't know what it looks like, but I've also never seen a reference to it for a 1975 USA market car.  Sounds interesting.

 

It would help you to know if your car is a Federal model, or California, or imported.  They have differences.

 

 

If you have an adjustable FPR you could drop a couple of PSI to change the rate of the Ford injectors.  Also noticed your bungy cord battery hold down with the battery on its side.  It doesn't even have to come completely free to short out, just slide forward a few inches.  Your problems are set to grow dramatically with one hard braking situation.

 

http://www.rceng.com/technical.aspx

Edited December 20, 2013 by NewZed

[Serban]

I noted in the last post, the car is a California model. The image I posted was from the Nissan FSM, page number EC-16. FSM is for a 75 model, so it may just be specific to that one. Here's the full page.

 

 

Still using the stock FPR for now. That picture is before I took out the Odyssey battery. I've got a full size one in there now strapped down good until I can come up with a mounting solution for the Odyssey.

[NewZed]

I have only worked with the FSM's like the one in the link below.  Your picture looks like it came from an FSM for a more modern car, with a more modern font and more modern parts.  Kind of weird.  Good luck with it.

 

Added a picture from EC-16 of the 1975 FSM.  Maybe there's a separate FSM for California, although the 1976 Owners Manual (can't find a 75) also refers to a floor Temperature Sensor, not a converter temperature sensor.

 

 

Edit - by the way, even if you do have an updated more modern, specialized FSM for your car, it should still have a full description of what the ECU uses to determine fuel enrichment, in the Engine Fuel chapter.  It will tell you if the catalytic converter temperature sensor is involved.  It shoudn't be though, unless it's using it's reading as a proxy for O2 sensor temperature, which I don't think you would have in 1975.

 

 

http://www.nicoclub.com/FSM/280z/1975/

 

http://www.xenons30.com/reference.html    (page 3 of the 1976 Owners Manual)

Edited December 20, 2013 by NewZed

[ctc]

My Skyline (1976) has that sensor, but it's JDM. The only thing it does on my car is turn a light off on the dash when the cat is at temperature. Leaving it unplugged, the light just stays on till the bulb burns out. Do you have a light in the dash for cat temperature?

[Serban]

There is a catalyst light on the dash. Don't think I ever saw it turn on though.

[Serban]

I put the sensor back in, not sure if it does anything different.

 

Wideband is also installed. At cruising speeds and part throttle, it's in the 15-16 range, full throttle in the mid to high 12s. Off throttle and idle in the low 11s. So it's a bit rich at idle. Can this be addressed with making adjustments on the AFM?

[9rider]

76 Ca 280z no sensor.

Cat light on dash..where is it? Never seen it in my life even newer cars.

Edited December 23, 2013 by 9rider