Pretty much as in the title. The engine light has appeared and my code reader shows a P0171. The car had a new exhaust flexi section three weeks ago. This is a lean mixture code, so has anybody suggestions about where I start. Levels are all OK and engine seems to run OK. The car does 30 miles most days, and recently went to Dorset and back, plus trips so done about 1000 miles in the last month.

My crystall ball (aka Google...)  Is telling me air leak or MAF, so I will go leak hunting when my son returns with the car.

 

 

Check: Servo vac hose, breather hose from breather module on rear of engine to inlet manifold (if it has this arrangement, what year/engine code is the car?), purge valve hoses.

Edited 6 July, 20187 yr by Wino

Thats very helpful Wino, thankyou. Its a 2002 car, so quite early. I'm not sure how to identify the purge valve and its hoses, but I have a Haynes manual to confuse me (I'm easily confused) 

 

 

In that case I think your breather hose goes up to the airbox, so much less likely to be the issue. Purge valve is a little round solenoid valve in black plastic casing, pipes in/out at the ends, two-way electrical plug on the side; near expansion tank, I think.

Piccy of purge valve...

 

 

Edited 6 July, 20187 yr by TMB

@Hyphons had exactly the same fault code on his (1.4 16v manual) it was too the point it wouldn't idle at all as it had such a huge air leak. The cause was the egr valve in his case being so coked up it wouldn't shut basically choking the engine. If it starts to have a terrible idle a very quick test is to unplug the egr. If it runs better it needs either a new valve or cleaning 

I had a look yesterday, and yes the breather pipe goes to the airbox on this one. I can't see any obvious chafes or leaks on either the servo vacuum pipe or the purge valve pipe. The car idles pretty well at 900-1000 rpm.  I did briefly unplug the purge valve and the software works as it immediately threw up that fault, so I reconnected and have cleared the faults and will try again. What else would cause a weak mixture, or send a signal suggesting weak mixture ?

 

I might just spray the pipes with a fairy liquid solution as that is excellent at revealing leaks as its quite difficult to see into all the nooks and crannies where pipes connect

Unplug the egr and see if it runs better. It's quite easy to spot, passenger side of the engine at the front, just under the engine cover. Grey plug

I havn't tried the EGR as I wasn't quite sure which one it was, but will do when the car reappears from my son's daily trip to work and back.

Just reset the ECU for now, Lambda probe will be the next logical thing to replace if it reoccurs.

19 hours ago, sepulchrave said:

Just reset the ECU for now, Lambda probe will be the next logical thing to replace if it reoccurs.

 

I was sort of heading in that direction. It has done 30 miles now without the engine light coming on. The car has done 114,000 miles in total and  whilst I should know whether its had a Lambda probe in the last seven years I'm not entirely sure, but I don't think it has.

 

 

Edited 11 July, 20187 yr by alfalincs