Oxygen sensor

[Clifford Pope]

Does the engine run noticeably badly, or is it running OK but with the light on?

If running badly, does clearing the code then make it run OK until next time?

What I'm getting at is that a momentary fault can trigger the light, but that doesn't necessarily mean the fault is continuous.
You've checked all the wiring to the power side of the sensor, what about earths? I once had recurring instances of the light coming on, then I reset it, then after a while it came on again. I was tempted just to unplug the bulb, but in the end someone suggested it could be a poor master-earth for all electricals other than the starter. That's a screw on the inner wing hidden behind the battery.

[User54]

Originally Posted by Laird Scooby

Was there a very slight misfire/cough/hiccough just before the EML came on again? If not, what were the circumstances immedialtely prior to it coming on? Had you just given it the beans to get up a hill for example?

Hi, no cough or anything that I noticed, the car runs perfectly as it did before the stupid light came on! Can't remember the exact circumstances as although I was checking the light frequently, nothing occurred that made me check the light, the second drive in particular was very gentle, it did take the light longer to come on, ~18 miles vs ~10 miles. Thank you for your help on this.

Originally Posted by Clifford Pope

Does the engine run noticeably badly, or is it running OK but with the light on?

If running badly, does clearing the code then make it run OK until next time?

What I'm getting at is that a momentary fault can trigger the light, but that doesn't necessarily mean the fault is continuous.
You've checked all the wiring to the power side of the sensor, what about earths? I once had recurring instances of the light coming on, then I reset it, then after a while it came on again. I was tempted just to unplug the bulb, but in the end someone suggested it could be a poor master-earth for all electricals other than the starter. That's a screw on the inner wing hidden behind the battery.

Hi, No it's running fine, it smells like it's probably running a bit rich which makes sense(?). I will definitely check the earth mentioned, thank you for the suggestion.

[Laird Scooby]

Originally Posted by User54

Hi, no cough or anything that I noticed, the car runs perfectly as it did before the stupid light came on! Can't remember the exact circumstances as although I was checking the light frequently, nothing occurred that made me check the light, the second drive in particular was very gentle, it did take the light longer to come on, ~18 miles vs ~10 miles. Thank you for your help on this.




Hi, No it's running fine, it smells like it's probably running a bit rich which makes sense(?). I will definitely check the earth mentioned, thank you for the suggestion.

Also worth checking your FPR - Fuel Pressure Regulator - on the end of the fuel rail. You'll need the engine running for this on idle, pull off the small bore vacuum tube from the FPR and put your thumb over the end of it. Keep it there for about 30 seconds and observe the stub on the FPR you removed the hose from. If any fuel comes out, even a drop, you need a new FPR as that will cause the problem you're experiencing now. Worth treating the car to a dose of this stuff as well to make sure the injectors are clean and not leaking :

https://www.halfords.com/motoring/en...te-247886.html

If your injectors are dirty and not sealing properly when they're meant to, it could be they are dribbling extra fuel in when they shouldn't which will make it run rich.

I'm assuming here you've checked the plugs and their gaps (0.65 - 0.7mm) and the HT leads are all secure and can't be lifted off easily? Also your rotor arm and dizzy cap are in good condition?

[User54]

A bit of an update:

• Checked the earth lead behind the battery; cable and all of the connections look perfect.
• Tried the FPR test, no sign of any fuel leaking out of the FPR.
• Checked the distributor cap and rotor arm, both look fine, they were replaced only 2,000 miles ago.
• Couldn't check the plug gaps as it looks like someone has 'borrowed' my plug sockets! The leads were all good and tight on the plugs though.
• I swapped fuse number 4 for a new one and gave the contacts a light clean.

The light is currently out but I suspect that is due to the battery being disconnected for 24 hours rather than the issue being fixed.