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Dead 02 sensors causing slight misfire?

StrangeRover

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(Last modified: by StrangeRover)
#1

Hiya gents i've put the old 38 back together and she runs, no leaks

However it has a slight misfire at idle, she's showing faults for both 02 sensors, would I be correct in assuming that they are most likely to blame for the misfire?

Annnnnd.

I'm looking at new sensors is there a specific type I need to get for the thor v8?

cheers all

H

leolito

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#2

If i remember right engine computer excludes O2 sensors in certain circumstances, such as cold start, wot, etc.
In your case, it depends on what "failure" is detected (i.e. slow response, open or short circuit. etc.).

Me, after playing and spending a lot of money on "universal" sensors, "adaptable" sensors and the such, buy only OEM.

StrangeRover

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#3

Thanks, it runs fine for a few seconds after cold start, but it's down hill from there.

As for fault codes it seems to show all of the above, slow response and open circuit.

Gilbertd

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#4

A duff O2 sensor will give 0V, which on a Thor, is seen by the ECU as a lean mixture. That will cause it to richen the mixture which can cause a misfire, or rough idle at the very least.

From what I understand, Thor doesn't like anything other than Bosch sensors.

StrangeRover

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(Last modified: by StrangeRover)
#5

Thanks Richard, am i right in thinking the thor uses Zirconia sensors and the gems uses Titania ?

Gilbertd

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#6

Yes, 0-1V on the Thor with 0V being lean, 5-0V on GEMS with 5V being lean (so failure has different symptoms).

StrangeRover

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#7

ok great..

Thanks.

Gilbertd

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#8

+1 on avoiding the cheap universal sensors. As my LPG system isn't too keen on the 5-0V sensors, I've got a 0-1V Zirconia in one downpipe purely to drive the LPG system. The cheap eBay jobs last about 6 months, so only use decent NTK ones these days. The one in there has been there for at least 3 years now.

Harv

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#9

I’m not up on what you had apart. As Richard notes above, the O2 sensor might be duff or it might be telling you the truth. If it’s telling the truth it could be caused by various things. Seeing both sensors (I’m presuming it’s the upstream sensors) are giving you a fault it isn’t likely to be a bad injector. You could have an intake leak somewhere downstream of the MAF sensor that affects both banks.

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