o2 sensor malfunctioning?

[RX25SE]

I just realized i had another screencap from EFI live, showing coolant temp sensor voltage along with the corresponding coolant temp.



Also, would an issue with the fuel pressure regulator, or leaking injectors be able to be identified with a fuel pressure test? Or is there a DIY method I can do at home?

Pressure reg can be tested with a pressure gauge connected. Disconnect the vacuum supply and fuel pressure should also rise.

Leaking injectors may cause rough running on initial start up along with a puff of black smoke but will settle to a normal idle quickly.

First test is a Delco suggested. Check vac line for fuel.

Paper towel idea also sounds good but Ive never tried it.

 

[CRCinAU]

My car seems to run rich at idle, to the point that it has strong exhaust fumes. Fuel econ isn't that good either. I was told that my o2 sensor could be the culprit. Had a look at it in EFILive, voltage was quite stable around 900mV, the test was done while the car was idling, at operating temp. Pic included.

Its interesting that I'm trying to troubleshoot the same issue here - the exhaust stinks of fuel at idle - to the point where I may as well just be evaporating fuel! My o2 sensor via efilive shows between 100mV and 450mV at various throttle settings (up to about 3000rpm in park). I'm trying to figure out a few more readings with Tuner Pro RT - but having a few issues with it displaying the right stuff...

 

[Bizmark]

Is the fuel pressure regulator the small round metallic object attached to the fuel rail on the driver side. Or is it that larger round object which is located behind the manifold elbow, which also bolts onto the throttle cable plate?

Also am i supposed to depressurise the fuel system before checking the fuel pressure regulator vaccuum hose?

 

[RX25SE]

The fuel pressure reg has a vacuum line running from it to the inlet manifold, usually mounted to the fuel rail with the return line coming off it. This is the line you check for fuel. Do this after the car has sat for a while.

Do not depressurise the system to test the reg. for leaks as you need the pressure to make it leak.
You will need to depressurise the system to replace the reg.

 

[Bizmark]

I didn't find a line running directly to the inlet manifold, though there was a small rubber hose running from the fuel pressure regulator to the elbow between the manifold and throttlebody, so that may be the correct hose?

Is there a special way to remove that hose from the fuel pressure reg or all that's needed is a hard tug? I also noticed that the hose was showing signs of degradation, ie: very fine cracks when pressure is exerted on it.

 

[RX25SE]

That's it, just give it a tug.

 

[CRCinAU]

Does this look like a crook O2 sensor or wiring to the sensor?

 

[RX25SE]

I can't see what the horizontal and vertical scales represent.
Is that 2mV to 13mV???

You should have a voltage range from about 1.0v to 0.1v every 300mS.

From the NGK website.

Using an appropriate connecting device, connect the sensor output to your oscilloscope; do not disconnect the sensor from the ECU. Run the engine at approximately 2000 rpm. A properly functioning oxygen sensor will show a rapidly fluctuating output voltage between approximately 0.1 and 1.0 volts. The time taken for the voltage to change from 0.1 V to 1.0 V (referred to as the lean to rich response time) should be about 300 milliseconds. A similar time should be measured when the voltage changes from 1.0 V to 0.1 V (rich to lean response time).

If the sensor output is constant or the response time is too slow the sensor should be changed. It is a good idea to check the oxygen sensor function at every tune up and before submitting cars for emission tests. A slow sensor will affect fuel economy. A new sensor will pay for itself by cutting fuel costs.

 

[CRCinAU]

Hmmm - The scale is from 0v to 0.25mV. That seems to be the limit of what I'm getting from it.

I'm wondering if its worthwhile to throw a multimeter on the sensor directly and see what voltage I get from it between ground and the probe. This way I can rule out any or all wiring / connector issues at the same time. I don't think I've seen the sensor get anywhere near 1v - from memory, about 450mV is the most I've ever seen via efilive.

 

[RX25SE]

A multimeter won't react fast enough. You need an ocilloscope.