Fuel economy

Hey guys, yet another question... I've been getting fairly average fuel economy lately; around 550kms to a tank of 98. (Car is an n15 series two sedan with a GA16 engine) However I have only gotten around 290kms to roughly a full tank this time. I don't thrash the car, the o2 sensor is new, fuel filter and air filter aren't very old, around three months, and the engine oil and filter were changed this weekend just gone. Is there anything I'm missing that could contribute to better fuel economy? The car has done a little over 170,000kms. Any insight would be helpful, cheers!

Pull spark plugs and inspect. Leaking injector maybe.

I'll check the spark plugs when I get a chance and see if they're all good. Is there a way to tell an injector is leaking? Or look for a wet patch around the injector? Thanks for the reply by the way

Assuming you don't have a fuel leak or a faulty gauge, then usually by pulling the spark plug you'll see one cylinder that has a very black plug, or is different to the rest. That's usually the one with a problem. At least its a start.

Injectors don't often leak from the body (but they can), they leak from the cap where the fuel squirts out and can drip and waste a lot of fuel. This way you don't physically see the leak.

Buy second hand injectors or take them to peps to get flow tested


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And the price for best user name goes to this guy ^^^^^^^


Whats going on here? Facebook link?

I changed the spark plugs yesterday, they had all burnt 'cleanly' so to speak, however plugs for cylinder one and two had some rust (I guess it was) around the base of the ceramic part of the plug? I'm not sure if that may have affected the idle, but will see how we go

The rust on the ceramic won't be the problem. If they're burning all the same the problem lies elsewhere.

Maybe try a fuel pressure gauge and check to see if it drops. But if you had a leaky injector sometimes you'll notice a issue trying to start it


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Curious to know how everything's going


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Sorry for the late reply guys. So I ended up getting near on 600kms to 38 litres on the first tank of fuel after doing the plugs; pretty happy with that! My idle is still a bit rough though (another issue). Might just have to deal with that one.

Maybe pull out your air flow sensor and give it a clean, possibly Iacv valve is also dirty.


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I need to clean the iac valve properly, I tried to split it in half but one of the screws that holds it together was starting to strip so I left it for the time being. No doubt that will probably be the culprit haha

Agh. That sucks mine started to just make sure you get the right screwdriver and push a little harder


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Quote:

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Originally Posted by SLO015

I tried to split it in half but one of the screws that holds it together was starting to strip...

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What do you mean?

Did this happen while you were trying to remove the screw/bolt?

Did you have the screw/bolt out and was trying to put it back in and this occured?

Did you round the head of the screw/bolt?

Very confusing description of what you where doing and what happened.

When he says "starting to strip" I'm assuming it's a philips head and that the bit was rounding out the philips head part?

I'd assume it was too tight he was trying to get it if and Nek minut stripped. Time to take her all off haha


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Late reply again, sorry guys. You are correct, it was a philips head and as I was trying to undo it it was starting to strip. I'll have to find a more suitable philips head that won't strip it as I got a price for a new iac valve from Nissan; 300 something dollars at trade price haha. I'll be cleaning it that's for sure! As for fuel economy, it's still been very efficient since the spark plug change.