P0171 - Fuel Trim System Too lean (Bank 1)

[TheStigP11]

Okay so our Micra management light keeps coming on. We recently changed the MAF on it as the last time the management light came on it showed the MAF was faulty. So i purchased a new one from eBay, fitted it and engine ran fine untill about 2-3 weeks ago. The engine management light came on, I plugged up the laptop and showed this time as P0171 Fuel Trim too Lean bank 1. Now what i notice is that when the Engine management light is on, the car seems a little sluggish and the idle isnt the best. When i reset the engine light when the engine is running the engine revs dip a little and then i get perfect idle. I take it for a drive and everything seems fine. The light seems to come on after fast engine speed has been done. when the light comes on it runs like a bag of spanners again.

When you start the engine when the management light comes on it splutters to life. If i reset the management light so its off the engine fires up healthy with no hesitation.

I have seen once when the old maf was in the engine that it showed a pending error code of O2 voltage low or something along those lines but this has never came back again.

Could this be the MAF again?? or something else?

 

[Scott]

Could be lambda sensor

 

[Dave_Ally]

It could be the lambda or MAF. This thread also suggests it could be related to spark plugs but I'm unsure as you have low idle also. It's exactly the same issue I've had with my car for months, P0171 comes up and its running rough at idle. Eventually after a few months of resetting the light the car will start to show other symptoms such as no power from cold start until it starts to get warm and kangarooing.

 

[TheStigP11]

This was interesting reading, http://www.blazt.biz/blog/allcars/109/fault-code-p0171-how-to-diagnose/

I watched all sensors ect and the MAF performed perfect, What i will do is change the Lambda and plugs again, I got a few set of new plugs kicking about so will try a higher heat range.

 

[Dave_Ally]

I just found out the other day they put Denso plugs in when they serviced mine before I bought it so have some Bosch FR8s coming to put in. Hopefully might improve things as I have changed the lambda once and and the MAF twice now (after the air temperature sensor on the side blew on the first replacement).

 

[frank]

measuring the voltage of the lambda on the fly will speak volumes :grinning:

 

[r-reg-sr]

i was told my volt meter might be reacting to slow to test the lambda
what could be used as i would like to do what your suggesting frank

 

[frank]

i was told my volt meter might be reacting to slow to test the lambda
what could be used as i would like to do what your suggesting frank

mine,s just a cheapo one mounted on the dash mate :grinning: it has a 1 sec refresh rate, which seems adequate

 

[Dave_Ally]

Just to update I now have a set of Bosch FR8DCX+ in and P0171 has lit up again tonight on the motorway after roughly 100 miles since the last reset. I'm getting to the end of my tether with this problem, especially as it's obviously overfuelling enough to throw the light on and the Denso plugs replaced were getting towards black (25% more than standard or something like that?) - need as much petrol as I can get with the prices always on the rise.

Don't really know what to do now, can't forever throw money at the problem as I keep ending up back at square one. Mine always tends to come on at speed (usually 60MPH+).

 

[frank]

if its taking a while to come on its probably the "longterm" fueltrim eh http://www.ilexa.co.uk/forum/index.php/topic,15884.msg74562.html#msg74562

 

[Dave_Ally]

Yes it seems most likely, it did this at first for a few months - ran fine after light was reset and it would come back on in 80-100 miles. Then it increased in frequency and eventually lost all power on first cold start after a MIL reset until it started to warm up and compensate.

Is it worth getting it checked for leaks and the injectors are OK?

 

[Stewpotz]

my mums Vectra was doing this at the start of the year, turned out to be a faulty MAF sensor.

it would be fine at low speeds/revs, but as soon as you reach the high stuff (on my mums 2.0CDTI Vectra estate it would start at about 4k revs depending on gear, or around 70-80mph if it was changed up at around 2.5k) the engine management light would come on and there would be zero power at all.