NOx Sensor & Poor MPG

[fordy]

Hiya guys

just popped in to have a look around for info on related issues with replacement nox sensors and poor mpg. About 9 months ago I had a nox sensor replaced, since then my mpg has gradually declined. pre fault I was getting 45 mpg, now I'm getting 35 mpg. I haven't changed anything else, fuel is the same, recent service, tyre pressure correct etc.

I just don't know if there is something that ties both replacing the nox sensor to the poor mpg. any suggestions would be greatly appreciated.

Ethan

 

[stefthecelt]

Hiya guys

just popped in to have a look around for info on related issues with replacement nox sensors and poor mpg. About 9 months ago I had a nox sensor replaced, since then my mpg has gradually declined. pre fault I was getting 45 mpg, now I'm getting 35 mpg. I haven't changed anything else, fuel is the same, recent service, tyre pressure correct etc.

I just don't know if there is something that ties both replacing the nox sensor to the poor mpg. any suggestions would be greatly appreciated.

Ethan

Check the coils mate!!

 

[spike]

Hi Ethan
If the engine is not misfiring then its less likely to be the coils. I'd start with a diagnostic scan as it may be a sensor problem - for example, a faulty water temp sensor could cause the engine to run rich all the time.
Sorry I can't think of an obvious link between the NOX sensor replacement and poor fuel consumption

Cheers Spike

 

[fordy]

cheers....looks like I might have to pay Skipton a visit

Ethan

 

[fordy]

well....not had chance to contact Mike. Today, on my way back from a bad days fishing, I developed a misfire and the engine management system light came on. It seems like it running on 3 cylinders, it pulls away very sluggish and sounds like a vw beetle

I guess it looks like the coil pack. Any ideas of costs and which parts to get for my 2004 1.6fsi. I have read that the earlier parts were very unreliable. Would it be better to replace all 4, or just the faulty one? BTW...was it ok for me to drive it home

I would really appreciate any help/advice.

Thanks Ethan.

 

[chb]

I replaced all four on my FSI at the same time, that way I know they are good!
I kept a couple of the "old, but working" coils as emergency spares.

So far this year my FSI has needed a NOX sensor and coils, this seems to be typical for 5 year old A2 FSI's, if I can now forget about them for another 5 years then I will be happy!

 

[chb]

By the way, the coil packs are a tight friction fit with short leads to them.
You will need a large flat bladed screwdriver and some patience to coax them loose. Be gentle!
Also DO NOT be tempted to lubricate the rubber on the coils to ease re-insertion/future removal. WHY? Well if you do (I used silicone grease) then you will make the rubber seal on the coil airtight, this creates a small pocket of trapped air around the sparkplug. The result is that as the engine heats up, the air expands and pushes the coil off!