shortbus

Lately I've been seeing weird stuff from my wideband. Up untill a few weeks ago, the car would run 14.7- 15.2 or so in normal driving. It would peg at 20.0 under engine braking, and high 10's to low 11's under full boost (peaking around 15 PSI). Now all of a sudden I'm running 14.6 to 14.8 all the time, boost, decel, cruising, idle. I'm only hitting boost long enough to see if it ever richens up, then let out as soon as it doesn't.

Here's what i'm working with... '86 951, Autothority chips, MBC, recent venturi delete, recent complete vacuum line replacement. Just replaced the FPR with a 3 bar today and installed a fuel pressure guage hoping to address this problem. Car is otherwise stock. Autometer boost and wideband gauges less than 4 months, 1000 miles old. It hasn't been that long since I checked all my grounds for other issues and all were in great shape.

Any ideas?

max_boost951

May be a stuck O2 sensor? Not sure if the system defaults to a certain value. Hook up a DVOM and check the mv's while driving to see if the sensor is switching.

refresh951

Could it be a problem with the WBO2? Does it feel the same since you started getting these AFR readings? DME O2 would not appear to be the issue as at WOT (TPS >60%) should be running open loop.

Paulyy

When you replaced this, did you notice anything different? was the original one 2.5 bar?

onspeed

Broken o2 im betting .

My lc 1 will max out at 22 on decel , i was under the impression that want it was overheating ...

Chris White

Some Widebands defalt to 14.7 when they are ‘off line’ (not working right).

AFRs should go to max lean reading under engine deceleration – the fuel injectors are turned off when decelerating. If they don’t turn off then your TPS is not set right.

shortbus

I suppose a TPS issue could also cause it to fail to richen under load? I'll check my TPS today. I know it's clicking at idle, but I haven't gotten the multimeter out to start testing it yet. Any suggestions on how to force it to richen or lean out at idle to test voltage from the WB02?

refresh951

From Clark's Garage:

Testing the O2 Sensor

1. Start the car and run until engine is at normal operating temperature.
2. Disconnect the O2 sensor and connect a voltmeter to the sensor plug.
3. Run the engine at approximately 2500 rpm.
4. Introduce propane into the intake to enrich the mixture until the engine rpm
drops by 200 rpm. You may be able to create the same affect by disconnecting the vacuum line to the fuel pressure
regulator. However, you'll have to plug the vacuum line to prevent a vacuum leak to the intake manifold.
5. If the voltmeter reading rapidly rises to greater than 0.9 VDC the O2 is correctly indicating a
rich mixture. If the voltmeter response is sluggish or the voltage remains below 0.8 VDC, the sensor should be replaced.
6. Secure the propane addition.
7. While continuing to run the engine at 2500 rpm, disconnect a vacuum line from the intake to cause a lean mixture.
8. If the voltmeter indication rapidly drops to less than 0.2 VDC, the O2 sensor is properly reading a lean mixture.
If the voltmeter indication responds sluggishly or remains above 0.2 VDC, replace the sensor.

gruhsy

Thanks Chris you just answered a wideband question for me. I wondered if that was the case when I let off the throttle and my wide band went to 22.4. It made sense in my mind and you confirmed it


"Shortbus" I'm curious you didn't use any engine cleaners lately did you? My Acura Vigor went through o2 sensors for a short time every time Acura cleaned the engine bay. It was happening to the car before I bought it off my best friend. He was the one that figured it out not the Acura dealer that the engine cleaner they used wrecked the sensor.

good luck fixing,

Jason

Black51

Wideband needs to be recalibrated?

Tom M'Guinn

My zeitronix did this on occassion too. Once the sensor had fouled, and once the connectors were not tight...

dillon410021

did the o2 wire get burned? Mine will read 14.7-14.8 with just a 9v battery hooked up to it.

shortbus

I figured out this evening that my WB02 harness routing was pretty bad. The connector from the sensor to the guage harness was melted to the crossover pipe. I couldn't find any damage to the wiring or terminals, but that doesn't mean that there wasn't any damage to anything internal to the connector. They only melting on the harness side was the clamp that holds the connector together, so I should be okay just replacing the sensor. Do I remember reading something about a resistor installed in that connector on the sensor side?