Engine bogs only AFTER MIL is cleared

[RobH]

New to the forum so bear with me.

I have a 1996 Olds Ciera, 3.1L. The check engine code I have had for quite a while is P0140 which I believe is the rear oxygen sensor.

Squirrels chewed my crank sensor wires so that code popped up. Repaired the wires, cleared the codes. The car would bog terribly until maybe one or two cycles after the check engine light came back on (the P0140 again) and then it acted like the thing would come back to life and run like a scalded dog. It's fine after that.

Just had a throttle position sensor failure. Repaired, cleared the code. The SAME thing happened.

What is going on? Does the rear oxygen sensor cause that much of an issue? I thought this one was not used that much by the ECM? My guess is that after a while the computer knows that the sensor is bad and defaults to some constant value and then the engine runs fine? Do I just need to replace the rear oxygen sensor? Strange.

[DefEddie]

Whatever the issue is,the car runs better after the MIL lights because it has disregarded or defaulted to different programming due to the failed sensor.

It runs like crap at first because the computer is acting on the faulty signal,it doesn't know anything is wrong yet.

Not the pc answer,but gives you an idea what's happening.
I didn't even take the time to look up a P0140,basic knowledge tells me it's a powertrain circuit code.
Offhand,i've not seen a rear 02 sensor cause such an issue-they have almost nothing to do with fueling.
Diagnose the code and repair it, whamo! issue gone.

[Schmieder]

Did you check around to make sure the squirrels didn't chew up anything else? Other wires, hoses, store nuts in your tail pipe, haha.

Darn squirrels. Buy an air rifle as preventive maintenance!

[DefEddie]

Good point.
We see cars come into our dealership same times of the year due to rats etc..
They ALWAYS chew either the injector,plug or coil wires. Never had much of an issue with them chewing other things like ckp sensors.

[RobH]

The P0140 code is the rear oxygen sensor. I have a scanner with real time data viewing and you can see that oxygen sensor stuck at 0.445 (I think) volts which I read is a default failure voltage the way I understand it.

I have looked all over for other bad wires and have found none. It was doing this before the squirrels chewed up the crank sensor wires too. I cleared a knock code before that also and the problem showed up after that too. Once the MIL came on for a while and I am driving I swear it feels like another two cylinders kick in. Fine after that. You can barely get the speed up enought to get it to shift before that.

[Azrael]

Which crank sensor had the wiring chewed? 7x or 24x?

[RobH]

Azrael,

I'm not sure what you mean by which crank sensor -7X or 24X. The connector was right next to the oil filter - whichever one that was - in the front of the car by the radiator.

I'm pretty sure I have that fixed - I'm getting engine RPM's on my scan tool looking at the live data. No other fault codes have popped up since the repair.

[bszopi]

On a 3100, the crank sensor is at the rear of the engine (7x, next to firewall) or by the pulley (24x). The sensors by the oil filter are the oil pressure sensor and the knock sensor. The one closest to the oil filter should be the knock sensor, IIRC.

[RobH]

I think the wires I fixed went to the pulley area.

What does the engine do if the front O2 sensor is bad? Maybe I have the rear and front mixed up and the front one is the bad sensor. Would the symptoms make more sense then?

[pocket-rocket]

The front one is the one that the PCM relies on for fueling. Poor fuel economy is one side effect since the PCM will default into a run rich state to prevent detonation from a lean condition.

[DefEddie]

.445v is about the right reading for the rear 02 sensor.
That sensor should not switch at all and stay pretty much constant if your cats are workng correctly.

The front 02 sensor will be just the opposite,it should switch back and forth with about 1/2 volt (your .445) being the switch point in the middle between the rich/lean transistions.

There is no default failure voltage for an 02 sensor,the pcm monitors the circuit-if the signal return is above/below a set amount it sets a circuit failure code depending on whether the voltage is above or below the limits.

The .445 would only be an issue if it were on sensor 1,the front 02-as it should not be constant.

Do you have a datalog to post up? (preferably a .csv document).

*do you have cat sims or anything similar (antifoulers?) to trick the pcm into tuning the cats out?
This code could pop up due to no switching on the rear 02 circuit within a givin drive cycle maybe,the circuit does switch a given amount when the pcm test's the cat monitor circuit by adding fuel and measuring bias/switch between front/rear sensors.
It would flag a no activity code if nothing happens during this monitor.
If your cats are clogged it would read no activity maybe due to no airflow around the sensor-it would explain the no acceleration.
But the pcm can't just default and make the airflow better,so i'm not alot of help.
And clogged cats generally throw other codes.

[pocket-rocket]

If you have a scan tool that allows live sensor data viewing, an old O2 will always react slower than a new O2 as far as voltage changes goes.

[DefEddie]

If you have a scan tool that allows live sensor data viewing, an old O2 will always react slower than a new O2 as far as voltage changes goes.

That is generally a different code though,it is the insufficient switching/slow response code-and generally indicates a sensor at the end of it's life.
Every code signifies a different condition or event.
He has a no activity code,which surprises me he even has the .445 voltage on the scanner.

P0030 HO2S Heater Control Circuit (Bank 1 Sensor 1)
P0031 HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
P0032 HO2S Heater Control Circuit High (Bank 1 Sensor 1)
P0035 Turbo Charger Bypass Valve Control Circuit High
P0036 HO2S Heater Control Circuit (Bank 1 Sensor 2)
P0037 HO2S Heater Control Circuit Low (Bank 1 Sensor 2)
P0038 HO2S Heater Control Circuit High (Bank 1 Sensor 2)
P0040 Upstream Oxygen Sensors Swapped From Bank To Bank
P0041 Downstream Oxygen Sensors Swapped From Bank To Bank
P0042 HO2S Heater Control Circuit (Bank 1 Sensor 3)
P0043 HO2S Heater Control Circuit Low (Bank 1 Sensor 3)
P0044 HO2S Heater Control Circuit High (Bank 1 Sensor 3)
P0050 HO2S Heater Control Circuit (Bank 2 Sensor 1)
P0051 HO2S Heater Control Circuit Low (Bank 2 Sensor 1)
P0052 HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0053 HO2S Heater Resistance (Bank 1, Sensor 1)
P0054 HO2S Heater Resistance (Bank 1, Sensor 2)
P0055 HO2S Heater Resistance (Bank 1, Sensor 3)
P0056 HO2S Heater Control Circuit (Bank 2 Sensor 2)
P0057 HO2S Heater Control Circuit Low (Bank 2 Sensor 2)
P0058 HO2S Heater Control Circuit High (Bank 2 Sensor 2)
P0059 HO2S Heater Resistance (Bank 2, Sensor 1)
P0060 HO2S Heater Resistance (Bank 2, Sensor 2)
P0061 HO2S Heater Resistance (Bank 2, Sensor 3)
P0062 HO2S Heater Control Circuit (Bank 2 Sensor 3)
P0063 HO2S Heater Control Circuit Low (Bank 2 Sensor 3)
P0064 HO2S Heater Control Circuit High (Bank 2 Sensor 3)
P0130 02 Sensor Circuit Malfunction (Bank I Sensor 1)
P0131 02 Sensor Circuit Low Voltage (Bank I Sensor I)
P0132 02 Sensor Circuit High Voltage (Bank I Sensor 1)
P0133 02 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P0134 02 Sensor Circuit No Activity Detected (Bank I Sensor 1)
P0135 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0136 02 Sensor Circuit Malfunction (Bank I Sensor 2)
P0137 02 Sensor Circuit Low Voltage (Bank I Sensor 2)
P0138 02 Sensor Circuit High Voltage (Bank I Sensor 2)
P0139 02 Sensor Circuit Slow Response (Bank 1 Sensor 2)
P0140 02 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
P0142 02 Sensor Circuit Malfunction (Bank I Sensor 3)
P0143 02 Sensor Circuit Low Voltage (Bank I Sensor 3)
P0144 02 Sensor Circuit High Voltage (Bank I Sensor 3)
P0145 02 Sensor Circuit Slow Response (Bank 1 Sensor 3)
P0146 02 Sensor Circuit No Activity Detected (Bank I Sensor 3)
P0147 02 Sensor Heater Circuit Malfunction (Bank I Sensor 3)
P0150 02 Sensor Circuit Malfunction (Bank 2 Sensor I)
P0151 02 Sensor Circuit Low Voltage (Bank 2 Sensor I)
P0152 02 Sensor Circuit High Voltage (Bank 2 Sensor 1)
P0153 02 Sensor Circuit Slow Response (Bank 2 Sensor 1)
P0154 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)
P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P0156 02 Sensor Circuit Malfunction (Bank 2 Sensor 2)
P0157 02 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
P0158 02 Sensor Circuit High Voltage (Bank 2 Sensor 2)
P0159 02 Sensor Circuit Slow Response (Bank 2 Sensor 2)
P0160 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)
P0161 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)
P0162 02 Sensor Circuit Malfunction (Bank 2 Sensor 3)
P0163 02 Sensor Circuit Low Voltage (Bank 2 Sensor 3)
P0164 02 Sensor Circuit High Voltage (Bank 2 Sensor 3)
P0165 02 Sensor Circuit Slow Response (Bank 2 Sensor 3)
P0166 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 3)
P0167 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 3

[pocket-rocket]

I didn't really mean about the code. I was talking about response time in general. Nice DTC list though

[DefEddie]

Lol,I love showing the oxygen sensor DTC list to people that say they need an 02 sensor becuase of a code.
Most of those codes when I see them are due to conditions in other places and the sensor is responding or because of circuit issues from things like oil soaked connectors or harnesses across the exhaust.

I work at Autozone part time as a manager,so I get the "I need an 02 sensor" crap all the time.
I've finally trained the other people working there to understand just cause it lists a component in the code-does not mean it is bad.
The customer's are a harder sell,till they try to return the part that didn't fix the problem.
(sorry sir,no returns on electrical parts.)