O2 sensor added to cat bypass

[squidmarks]

I've been having some issues getting my mixture right, so I thought I'd add the O2 sensor into my cat bypass both to help set my mixture, but also I will try the mixture control system that comes with the SC (I've been running without an O2 sensor in open loop mode).

Right now, I'm getting ~0.87V on the sensor with the engine warmed up. It was close to 1V until I turned the mixture adjuster down, then fluctuating under 0.5V (too lean), now it seems happy at 0.87V. Does that sound about right?

I'm going to connect the O2 sensor into the system and see how it drives. Given the slow response time, I gather that this mixture control circuit has a pretty slow control loop.

Geoff

Here's the modification of the cat bypass:

Cat bypass and original cat:



Hole drilled on bypass:


Bung welded on, O2 sensor test mounted:

[don gilbert]

looks good geoff. A properly tuned cis car with working lamda is a much more enjoyable car to have. I worked on both and the 02 cars can get way better gas milage and can be tuned to perform just as good, or in most cased better than a non 02 car or a car that has had the 02 dissable and the mix turned up to 3.5 You will more than likely need a new relay to, listen for the clicking under the pass seat, and then get out the test lite and check, these relays run pretty warm and fail often, get the correct one from our host, the cheap plastic ones wont work long. I like to test my system with a dwell meter as per the bently, its the easiest way.

[don gilbert]

one more thing, do not solder your 02 connection, use a quality weather pack conn. from napa or such, the solder affects the mili voltage traveling that wire

[squidmarks]

Checked the relay on the bench, it works fine and it clicks when the ignition is turned to "Run." Bentley says the frequency valve should "buzz." Mine is emitting a high-pitched whine, but I wouldn't say its buzzing or vibrating. Should it be buzzing or whining?

EDIT: It was actually my voltage regulator whining, when I grab the frequency valve when the engine is running - no buzzing. O2 sensor is not connected yet - should it be?
EDIT#2: It appears my 15C sensor is not functioning as I don't get continuity to ground thru it (it is definitely above 15C). But, grounding the connector to the does not get my freq valve buzzing.

Geoff

[don gilbert]

they all sound a little different, some you cant even hear, but it sounds like yours is ok, but only a dwell meter will tell you what its doing (duty cycle). the ecm is reading the voltage from the 02, and sending a signal to the frequency valve, which is just an in-line injector relieving the press. in the lower chambers of the fuel dist. richening and leaning your mixture to keep at stoiche during idling and part throttle. Do you still have the test plug on the rt side of the engine? little round thing with 3 wire coming from it. You can get a cheap dwell meter at the zone for 50.00. I have found it essential and quick for making afr adjustment ( i adjust my wot mix for temp changes and barometric changes week to week sometimes)

[don gilbert]

sorry didnt finish you post. pull the pass seat and use sandpaper to clean all the grounds for the ecm, check the main ecm gang connector towards the front left of the engine compartment and clean. are you sure you have the correct bosche metal cased relay and voltage going to the ecm? f/ valve should buzz when fuel pump is running, engine started or not

[squidmarks]

Yes, I've got a metal-cased relay and its functional. I tested it on the bench and I can feel it click when the ignition key is turned.

The dwell meter test plug, its on the left (driver) side of the engine, right by the fuse box, round with three connectors - if so, yes its there.

I checked the ground under the seat and got continuity b/w the copper connector and ground. I took off and put back on the other main connectors under the pass seat.

What does the main gang connector look like? How many wires? Is it close to the dwell test plug? EDIT: Found it - behind the blower motor - connected fine.

Thanks for your help.

Geoff

[don gilbert]

its hard to see and get to. it looks just like your main engine harness conn. where it hooks up to the body harness on your elec. panal. its behind the blower motor up againt the firewall

[don gilbert]

Geoff you are going to have to unplug it and clean it with some spray lecto cleaner. the term. are alum. and most likely are corroded.

[squidmarks]

Ok, I'll give it a cleaning tomorrow morning. At one point during my rebuild, I had it out on the floor like you show. While I don't specifically remember inspecting/cleaning that connector, I likely did. I will check it again tomorrow, tho. Thanks.

Geoff

[squidmarks]

I couldn't stay away from it. I checked and cleaned the main connector behind the blow motor - everything looks good.

I re-checked the relay and it definitely clicks on when the fuel pump relay turns on.

Geoff

[squidmarks]

After sleeping on it, I got up this morning and re-checked all connections under the seat, re-verified the relay was working by measuring 12V on pin 8 of the ECU connector. Because I didn't want to wake my still sleeping wife (my workshop is below our bedroom), rather than start the engine to get the fuel pump going, I jumpered the fuel pump relay so it would turn on in the ignition "run" position. So, I got 12V on pin 8 of the ECU connector and both its grounds were fine, so I re-connected it back onto the ECU. When I turned the ignition to run again to check something else, I heard the vibrating freq valve! Everything has been working all along! When I started the car up (wife now awake, anyway), and put my fingers on the freq valve, I could not discern its vibration from the rest of the normal engine vibrations. Only when the engine was off and it was forced to vibrate by jumping the fuel pump solenoid could I verify its operation.

Ok, it looks like I have a faulty 15C switch (right cam chain cover), tho, as yesterday when I was checking it, the switch did not show ground when the engine was warm.

Can I use the disconnected O2 sensor output to set my idle mixture? Yesterday I had it reading ~0.87V. I thought that a reading closer to 0.5V might be correct and 0.8-0.9 would be running rich. With the lamda system working, I assume you'd want it on the leaner side, right?

Thanks.

Geoff