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High fuel trim - possible causes?

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo's stylish, distinctive P2 platform cars sold as model years 2001-2007 (North American market year designations).

2001 - 2007 V70
2001 - 2004 V70 XC (Cross Country)
2004 - 2007 XC70 (Cross Country)
2001 - 2009 S60
2003 - 2007 S60 R
2004 - 2007 V70 R

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cdr
Posts: 1
Joined: 12 October 2010
Year and Model: V70, 2000
Location: England

High fuel trim - possible causes?

Post by cdr »

Hi,

My first post here, so go easy :D this is also about my first Volvo, which I'm really pleased with apart from a few niggles!

I'm getting really poor economy with my 2.4T V70 (B5244T3) at the moment - the long term fuel trim fluctuates between 15% and 25%. I'm surprised it doesn't throw a code with an FT that high.

It had a slight miss fire, rarely noticeable but would show up sometimes around 2k RPM - I checked the coils and one was burnt so I replaced it. Fitted new plugs while I had them out, but the old ones looked healthy enough. The miss fire has gone which I hoped would bring the LTFT down but over a couple of hundred miles it hasn't changed.

I occasionally get a 0333 (knock sensor 2 circuit high bank 2) code along with an "Emissions system service required" warning and the CEL. This usually happens after a long trip - it wont light up on the trip, it'll come up (before I start the engine) when returning to the car.

I'm not really sure what to do next with this - I could replace the knock sensor & wiring but it feels like this is a side effect of the actual problem.

If this was your car, what would you look at next? MAF, Lambda sensor?

Thanks in advance for any advice you can offer :)

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