2004 pulsar runs rich

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2004 pulsar runs rich

Postby fraserae » Tue Nov 15, 2016 7:43 am

Hey guys

I have a 2004 nissan pulsar QG18 engine that runs rich. Clouds of black smoke. No fault codes logged. Has 5.8 m/s injector pulse at idle. Only sensor I could fault was front oxygen sensor voltage was low. Replaced this sensor and injector pulse back to 3 m/s at idle and fuel trims starting to correct themself. Thought it was fixed.
Car came back after 3 weeks running rich again. Oxygen sensor dead again. Changed sensor and car runs better. Am I missing something? Thinking exhaust blocked but drives ok. Will check back pressure next.
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Re: 2004 pulsar runs rich

Postby Tronic » Tue Nov 15, 2016 2:31 pm

Hi fraserae!

Could be bad luck, but probably not, three weeks is fairly short life for the poor O2 sensor... I do not know if a clogged exhaust system could cause this sudden death after so short period of time. May there be, for some reason, an crack somewhere that allow coolant to enter the exhaust? Have you checked the O2 heather? Just guessing here and do not know even if this could happen; if there is a PWM controlled heather that accidentally put continuous B+ and thus, causing the element to die. That is my two Swedish crowns... :wink:
Last edited by Tronic on Wed Nov 16, 2016 7:11 pm, edited 2 times in total.
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Re: 2004 pulsar runs rich

Postby STC » Tue Nov 15, 2016 9:30 pm

Thinking exhaust blocked but drives ok


Would it drive OK with a blocked exhaust ? I don't think it would. The two O2 sensors that you have removed, are there any signs of contamination ?

If it has an Air Mass then that will be a good indicator of a blocked exhaust.
Where did you get the New O2 Sensor from ? there are a lot of counterfeit parts being sold nowadays ? (I am in the UK)

Tronic makes a good point, is the heater circuit shorted and permanently on ? What is the circuit design ?

The Pulsar is not a car we see very much of here and I cannot find a wiring diagram. Some years ago we did see Nissans Micra's where an internally shorted O2S2 would throw fault codes for O2S1. If I recall correctly Nissan issued a TSB instructing Both O2S1 & O2S2 should be replaced a pair with modified Components.
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