Codes 85 & 91

[MikeC]

I changed my clutch the other day and now the check engine light comes on after about 5 minutes of driving. It goes off after the engine is turned off and come back on after driving for about 5 minutes.
I pulled the codes abd got an 85 and a 91.
The table I have lists 85 as canister purge solenoid circuit failure and the 91 as oxygen sensor voltage always lean on bank #2.
Could the oxygen sensor have been damaged when I took the exhaust off to change the clutch? What else could cause this? There was no check engine light before the clutch change.

 

[MikeC]

I cleared the codes and went fro a little ride. The light came back on. I pulled the codes again and now I'm also getting a code 41, oxygen sensor voltage lean on bank #1 - No EGO sensor rich/lean transition detected bank #1. Any ideas on what could be causing this? Whatis the EGO? Exhaust gas o???

 

[superhuaman]

ego = exhaust gas oxygen
the sensors will set those lean codes if they're not plugged in or if the wiring is open

 

[HISSIN50]

Or if the sensor is broken.

FWIW, if you buy a new one, be sure it's a HEGO (Heated EGO - sounds like something Freud would talk about ).

I agree with the above - check that it's plugged in. If so, undo the connection and look for oil inside the connector. Clean, etc as appropriate.

Make sure the heater wiring is working too. This gets the sensors functional within 30-120 seconds of start up, even on a cold motor.

You can check the signal wire for switching. It should pulse from ~ .9 volts to .1 volt at least once a second.

Good luck.

 

[MikeC]

ego = exhaust gas oxygen
the sensors will set those lean codes if they're not plugged in or if the wiring is open

Thanks. I checked, the connections are clean and tight. Wiring looks good. Would bad sensors cause it to show lean, or only unpluged or open wiring? Seems like a big coincidence that both banks/sensors have problems at the same time. Anything else it could be?

 

[MikeC]

Or if the sensor is broken.

FWIW, if you buy a new one, be sure it's a HEGO (Heated EGO - sounds like something Freud would talk about ).

I agree with the above - check that it's plugged in. If so, undo the connection and look for oil inside the connector. Clean, etc as appropriate.

Make sure the heater wiring is working too. This gets the sensors functional within 30-120 seconds of start up, even on a cold motor.

You can check the signal wire for switching. It should pulse from ~ .9 volts to .1 volt at least once a second.

Good luck.

I cleaned the connectors with brake cleaner and blew tham out with compressed air. So there should not be any oil in there. Are Ford replacement sensors better than aftermarket or are they the same.

 

[HISSIN50]

There's some ambiguity on the brand of O2 question. Some say that Bosch is OEM while tuners have noted that Motorcraft O2's have better heater elements.

You wont go wrong with either. Should be 40-50 bucks for one.

Good luck.

 

[superhuaman]

well it was one first, then the other one too, right? how many miles are on them?

 

[MikeC]

well it was one first, then the other one too, right? how many miles are on them?

Yeah, I changed the clutch. Then the check engine light came on, showed code 91-bank #2 lean. I cleared the codes, drove the car again, light came on again. This time it showed codes 41 & 91-banks #1 and 2 lean.
I got the car about 3 weeks ago with 130K miles. The sensors are Ford parts so I bet they are original and need replacing anyway.

 

[superhuaman]

couldnt hurt...its possible that you damaged them when you took them out or when you took out the h pipe with them installed (idk how you did it). they are ceramic and metal, so theyre fragile like spark plugs

 

[HISSIN50]

I missed the part about both banks spitting O2 codes. I'd check for a vac leak too.

Good luck.

EDIT: the last two posts were made while I dilly-dallied.

 

[MikeC]

I took them out before taking out the H pipe. I thought I was pretty gentle them. I did put a bit of antisieze on th e threads but that should not affect anything.

 

[MikeC]

I missed the part about both banks spitting O2 codes. I'd check for a vac leak too.

Good luck.

EDIT: the last two posts were made while I dilly-dallied.

I checked for a vac leak by spraying starter fluid around the manifold but got no reaction. I did test the starter fluid by making my own vac leak and spraying it near the hose, the RPM went way up.

BTW: car runs fine. good idle, no noticable loss of power. At least I got a good deal on the car.

 

[jrichker]

The antiseize is usually conductive. Get it in the wrong place and the O2 sensors quit working. I do recommend using antiseize, but only sparingly on the last few threads near the base of the sensor.

 

[MikeC]

Or if the sensor is broken.
You can check the signal wire for switching. It should pulse from ~ .9 volts to .1 volt at least once a second.

How do I measure this voltage? Unplug sensor, run car and measure at connection with O2 sensor disconected?

 

[jrichker]

Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.

The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

 

[superhuaman]

that's right, i forgot...on some cars that i've seen, the o2 ground is on one of the bellhousing bolts. check where yours is, since you had the tranny out...

 

[MikeC]

OK, I have no vacuum leaks that I can find and the orange wire is grounded to the back of the engine. I don't have an analog multi-meter so maybe I'll just replace the sensors anyway, I think they are pretty old.
Come to think of it, I haven't driven the car much since I bought it three weeks ago and since the check engine light goes off after every restart and dosen't come on all the time, it could have been doing this since I bought it and I never noticed. And the code 38 is gone now.

 

[superhuaman]

code 38? you didnt mention that before, i dont even know what that is.

 

[MikeC]

code 38? you didnt mention that before, i dont even know what that is.

Long day. Should have said Code 85. I don't know where I came up with 38?