Now owner a few niggles

[Colin RedGriff]

I bought a 2005 1.8 Zetec a few weeks ago as a cheap runabout. Mostly its fine but there are a few things that are bugging me. 

The car has been regularly maintained and seems to be mostly in pretty good condition for a 10 year old car that has done 115K. I just put it through an MOT with no issues other than a blown side light bulb.

Firstly the engine warning light comes on - I've got some OBD software so I can read and clear the fault - the fault code is p0171 system is too lean bank 1. I know this is usually caused by an air leak on the intake but I would have thought that would cause it to happen almost immediately the car was  run. If I clear the fault; the car will run fine and the fault light will not come back on straight away. For instance I cleared the fault on Saturday and then proceeded to drive for over 200 miles without the light coming on. This was mixed motorway and town driving including heavy traffic and involved at least one stop, cool down and restart. The light came back on sometime on the way home on the motorway. Other times I've gone for days without the light coming on.

Second issue is a misfire this only happens when the fuel gets down to about 1/4 full on the fuel gauge and is worst when going round right hand bends, roundabouts or right turns. The car will hesitate and misfire but once I straighten up it will clear and run fine. Idling on the drive the car runs fine and there's no indication of a problem. Is this likely to be just the gauge being wrong and the car actually running out of fuel, some sort of problem with the fuel pick up in the fuel tank or some other issue?

The misfire and the engine warning light issues don't appear to be linked. The misfire will happen with the light not lit and the warning light can come on at any time.

Lastly starting seems a little hit and miss. The car has never failed to start but it will sometimes take 2 or 3 attempts to fire. It is more likely to happen if the engine is warm but it has happened on a cold engine as well. Engine turns over nicely (the battery was replaced by a previous owner) and once it has started it runs fine.

I've got a comprehensive set of tools and happy to do some spannering. Don't want to spend a lot of money getting a garage to fix it because the car isn't worth that much money. But I would like to get these niggly issues fixed.

Any ideas of things to check or test?

 

[Colin RedGriff]

A bit more information on the fault code. I hooked up the  OBDlaptop today and tried to investigate this a bit further. Once the car was warmed up the short term trim was between 0 and + 2 or 3, the long term trim was higher at +20-24 which seems higher this at idle (850 rpm).

If I press the throttle the short term trim rises to 16 or 20 and the long term trim drops down to 0-2. I think this rules out an air leak but can someone confirm?

I'm guessing possibly a dirty MAF so I'll give that a clean as it's an easy thing to try

[Colin RedGriff]

I did a mini service and replaced air filter, fuel filter and spark plugs to try and fix the ongoing problems. I also cleaned the MAF. I checked the air intake pipe for holes and cleaned it up.

The old air filter was pretty dirty, one of the spark plugs had cracks in the ceramic and another looked to have tracking on it. I was hopeful that this would improve matters but so far it hasn't helped the starting issue. Still waiting to see if the engine warning light will stay off.

I've put a spark check light in and I'm getting a nice regular spark on each cylinder. I also did a peak KV check and everything seemed okay.

Running out of ideas now.