VR 304 O2 sensor issues

[scott_dont05]

Hey all,

Thought I could have answered my problems by trawling this site but I am at a dead end.

Car is VR Calais with 5l auto. Just won't rev past 3-4k when coolant temp has got up past 85-90 deg, coughs and splutters until you back off the right foot.

Used Tunerpro, found out O2 sensor voltage is dropping off to almost zero under heavy load. Replaced sensor with Bosch 2 wire, no change.


Disconnect O2 sensor, car runs fine.

Checked wiring to PCM from sensor plug, fine. Checked earth from sensor to PCM and PCM to body, fine.

Tried another PCM from 5l auto, no change.

Ran new wiring from O2 sensor to PCM, no change.

About ready to just run it without the O2 sensor, it's not a daily driver.

Would appreciate any insights anyone may have, cheers.

 

[07GTS]

sounds like u need more fuel, check the pressure when the event happens cos a 02 sensor when in open loop or WOT should read about the .800-950mv range. it is no longer controlling fuel but u can see if its showing about 0 mv then its bad lean, could be pump or filter on way out or blocked

 

[scott_dont05]

sounds like u need more fuel, check the pressure when the event happens cos a 02 sensor when in open loop or WOT should read about the .800-950mv range. it is no longer controlling fuel but u can see if its showing about 0 mv then its bad lean, could be pump or filter on way out or blocked

Thanks for that, I wasn't aware of those values, that is interesting.

I thought it was a fuel supply issue initially as well, changed the filter and the pump is only 12 months old.

The reason I don't think it is fuel related is as soon as you unplug the o2 sensor (PCM uses presets), the problem goes away and it will will rev all the way out.

I will however check fuel pressure/regulator when I get the chance, cheers.