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Matt
Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 20611
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 2006 Nissan 1.2 Micra S model. Just over a year ago

Customer Question

I have a 2006 Nissan 1.2 Micra S model. Just over a year ago it had the downstream oxygen sensor replaced by my local Nissan Dealership due to the car misfiring, having a very bad tickover, almost cutting out and having variable speeds when driving along. A warning light also came up on the dashboard console. I was told that the other oxygen may at sometime in the future.
The car experienced the same above problems 2wks ago - apart from no warning light on the dashboard console. I therefore took it to my local (not Nissan) garage as it was barely driveable. They replaced the spark plugs, which improved the car's tickover but it wasn't 100% cured.
I then drove it to my local Nissan Dealership to see if they could fix it. They had it for 4.5 days and after numerous tests they concluded that they didn't know what was wrong with my car. They also said that it's not the other oxygen sensor due to no warning light appearing on the dashboard console and their computer software did not detect that it was the sensor.
The car is driveable but when idle or in traffic jams and generally driving along the tickover is not at all good.
Could I insist that the other oxygen sensor be replaced or could it be the battery ?
Thanks in advance for your help !
Submitted: 1 year ago.
Category: UK Car
Expert:  Matt replied 1 year ago.

Hello

if its the oxygen sensor thats after the catyslt ( the 2nd 1 on the pipe after the engine) then it won't have too much effect any way - if its the 1st 1 then yes it may be wise to replace it but before that check for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.

this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst

The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers

Also

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

Expert:  Matt replied 1 year ago.

Hi

do you still need help?

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