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1990 Renix SMOG, CA problem with running Rich/Lean

90XJ_Seth said:
Under the hood tonight, checking all my electrical connections with my shiny new analog multimeter... what do I finally find?... The O2 sensor harness on the vehicle side is falling apart (One of the wires doesn't even stay in place, it just slides in and out randomly, you know the one that is supposed to send the alternating voltage). The TPS sensor harness is literally disintegrating inside the weatherpak. The MAP sensor connector is also having a rough time. Time to get some decent connectors and rewire those little buggers. Ten 3-pin Weatherpacks arriving at my door tomorrow for the refresh. Maybe that's why I couldn't get a consistent voltage out of the O2 sensor... How did I refresh all the grounds and not even notice that the connectors were in such bad shape?!?!? I feel like an absolute fool right now. I hope that this refresh gives some solid results. Fingers Crossed.
Click to expand...

Note that the TPS/ECU 3 pin and MAP sensor weatherpack look the same, but they are not. Not sure where you bought them?

I had to use an exacto knife to trim some plastic on my TPS spare connector to fit the MAP sensors.
 
cruiser54 said:
Yes. It's normal ground is the dipstick tube stud. The ground can me tested also.
Click to expand...

Thank you Cruiser54 an EcoMike.

Ok, so I will check the ground which should read no voltage when off(any ohm reading?).
Then reverify that the grounds are clean and clear at the dipstick.
Once that is correct, on no key I should have 5 volts at the O2 sensor (black wire) and 12-14 volts at the orange wire.
Then when key and engine on the O2 sensor should oscillate between 1 and 4 volts.

Also carefully repair the MAP connection if possible and TPS as well. While looking for the poor solder job to the brown and white map sensor wires.
 
90XJ_Seth said:
Thank you Cruiser54 an EcoMike.

Ok, so I will check the ground which should read no voltage when off(any ohm reading?).
Then reverify that the grounds are clean and clear at the dipstick.
Once that is correct, on no key I should have 5 volts at the O2 sensor (black wire) and 12-14 volts at the orange wire.
Then when key and engine on the O2 sensor should oscillate between 1 and 4 volts.

Also carefully repair the MAP connection if possible and TPS as well. While looking for the poor solder job to the brown and white map sensor wires.
Click to expand...

No need to answer that question EcoMike already posted the previous forum answer.
 
After repairing the o2 harness and before connecting the sensor, I checked ground to battery .4 ohms, perfect :
ecu to harness 5 volts unplugged, perfect :
tried to check orange to ground, sparked when I grounded it then no voltage. Ideas?
 
Clarification. I had 14 volts yesterday but when I fixed the harness today and checked with multimeter it sparked at the ground and stopped reading any voltage. Multimeter reads other voltage OK. Is there a fusible link or am I chasing a wire splice issue potentially?
 
90XJ_Seth said:
Clarification. I had 14 volts yesterday but when I fixed the harness today and checked with multimeter it sparked at the ground and stopped reading any voltage. Multimeter reads other voltage OK. Is there a fusible link or am I chasing a wire splice issue potentially?
Click to expand...

Is there any reason that the orange voltage wire at the O2 sensor harness would have sparked at the ground and then stopped reading any voltage at all? I know I connected the positive lead before grounding.
 
The orange wire at the sensor is the heater circuit. If you grounded it, you likely blew a fuse.
 
Saudade said:
The orange wire at the sensor is the heater circuit. If you grounded it, you likely blew a fuse.
Click to expand...

That's what I was thinking but I can't seem to find a fuse that's blown and none of the fuses are rated for the relays or O2 sensor.

I did find something Interesting, out of the five relay contacts for the O2 relay, two are ground at perfect 0 voltage (Center, and nearest the Battery), two are live at 12.9 volts (nearest to the firewall and nearest the coil). However, the top (Nearest the passenger side fender) is showing 10.9 volts. The relays won't click on when inserted with power and engine on.
 
When you say ground at perfect 0 "voltage", do you mean resistance?

The oxygen sensor is equipped with a heating element that keeps the sensor at a consistent temperature under warm-up and idle conditions. This allows the engine control system to enter "closed loop" mode of operation much earlier, and to remain in "closed loop" during extended idle periods.

The heating element of the sensor is controlled by the ECU through the O2 sensor heater relay. This is a normally closed relay that supplies voltage to the sensor under warm-up and idle conditions. When the ECU receives information from the MAP and speed sensors
indicating that the sensor will stay heated due to exhaust gas temperature, the ECU opens the relay to stop voltage to the heating element.

So with the key on, engine running at idle, the relay will be closed (un-energized).

The 4 relays are the same, you can try swapping them out if you suspect relay issue.
 
So according to the standard relay schematic I found, the weird voltage I am having is at pin 87 which is registering 10.9 volts. 86 and 30 register at the 12.5V with power off and around 13-14 with power on. 87 and 85A read correctly as well. I am wondering if it is an issue with the fuel pump and ballast or even that relay as they feed the O2 sensor relay.
 
The power to the orange O2 heater wire goes from the battery to the rectangular ignition relay by the battery (big fat post IIRC), to a fuse link about 12" away, to the O2 heater relay then to the O2 sensor. With ignition switch on (not off), engine not started that orange wire should be a good 12 volts. Those O2 sensor wires can get too close the exhaust manifold and get damaged.
 
Today's journey, unclipped the relay connectors and the O2 relay (nearest battery) had one of the center orange wires (87A) brittle and exposing bare copper for 3 inches from the connection. The wire itself is in good condition so I E-taped it and set it back in place. The fuel pump relay seems to be working correctly because the second I pull it the motor cuts out. Rewired the TPS, and MAP weatherpacks (had to make a few small cuts on the MAP male side to make it fit so thanks for the tip). Can't find a fusible link anywhere in the engine harness within 12 inches of the main relays ECOMIKE and I pulled the battery and the relay harness to look underneath it. The exhaust manifold is not in contact with the harness and doesn't seem to be melted.
 
Also, I'm getting no voltage from the center post (87A) when the car turns on when testing if the relay is working. Changing the relay doesn't help. I feel like I'm searching for a short or a fuse now.
 
Okay, so I may have narrowed it down to the yellow wire on the relay connection. The schematic diagram says it runs to a point where the alternator and transmission control unit both connect to the Electrical system. It runs at just under 11 volts and seems to be doing something odd with voltage. I jumped the O2 relay connector with 16 gauge wire (not plugged into O2 sensor) and found it was sending approximately 13.8 volts to the O2 sensor so the orange wire is transmitting fine.
 
I come to you with my tail between my legs, it was a bad relay. I thought I tested it well. I feel like a fool. I have 14 volts where it belongs and the correct relay in the right spot.
 
weird voltage also solved, it is the voltage coming off the ballast regulator for the fuel pump. Right now I feel like a fool but I sure do appreciate all your guys' help.
 
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