Hi everyone.  I was wondering if anyone could give me some advice on a problem that my daughter is having with her car. She bought the car earlier this year (as a private sale).  After having the car after 2/3 weeks the EML(engine management light) came on.  We contacted the seller. He tested the car using a code reader.  I dont remember the actual code, but it was the top lamda sensor that was causing the problem (bank1 sensor1 I think).  The engine seemed to be running fine, with no other problems.  He used the code reader to reset the EML.  Unfortunately the EML came on again after a few weeks.  He then replaced the sensor with another one and reset the EML.  Unfortunately the EML came back on yet again after a few weeks.  My daughter tried contacting the seller again, but got no response. I went with my daughter to a friend of hers to test for the code again.  It indicated the same problem again.  Over the last year I have been extremely busy with work, and did not attempt to contact the seller myself.  I will try and do that soon.  The engine still runs fine and my daughter has been using it with no problems.  A little bit of history with the car:- The car apparently had a new engine fitted (ford recall?) before the previous owner. When my daughter bought the car it had done about 50,000 miles since the engine replacement.  Now I don't know what an engine replacement actually means?  We do have information of the garage that did this work, so I will now try and contact this garage. Oh and one other thing, my daughter did notice that on one occasion the EML light come on was after the car had not been used for over a week (could be a coincidence?).

Now that I have a little bit more time, I am thinking of putting Forscan on my old laptop and buying an ELM 327 adaptor.  I could try and replace the lamda sensor again with a good quality one (in the hope that the lamda sensor that the seller used was also faulty).  However I am very sceptical that this is the case, because exactly the same problem occurred with the original and the replacement.  Maybe, I should look at the possibility of testing the sensor before going ahead and buying a new one?

A few more points:-

1. Would Forscan help me diagnose this problem in more detail, especially with live data.  Could anyone be kind enough to help guide me to diagnose this problem?

2. When the engine was replaced, I assume that the original turbo-charger could have been moved to the new engine?  Maybe the pipes/connectors of the turbo-charger are not air-tight? Any advice as to what pipes etc in the engine I should check to make sure that they are not causing the problem?

3. The car's MOT is due late November.  If necessary I will reset the EML before the MOT, in the hope that the car will pass the test.  As I say it is running smoothly, with no problems. Is there a way that the EML light could be disabled before the MOT?  I do want to fix the problem, but obviously fixing it before the MOT could be a time issue.

Thank you so much for reading this.  Any advice would be welcome.

Thanks

Try fuel from another fuel station.

Has the car ever run on high speeds?

From time to time it is required, especially on 3rd gear.

 

What engine is it?

And, as Bol suggests, try some better quality fuel from a different station, preferably E5 to see if the problem goes away.

And 50,000 miles. Have the spark plugs been changed?

But, yes, you need FORScan and see if you are getting any codes, go for the V-Linker cable it's more reliable

Thank you for your help.  My plan is to service the car in a couple of weeks.  I plan on changing the spark plugs, air filter. oil filter and oil.  I will get FORscan and reset the code. I will google V-Linker and purchase one.

By the way the engine is a ecoboost  1.0 petrol engine.  I knew that it was a good idea to run diesels at high revs to clear them out, but I did not realise that this should also be done with petrol engines??

Thanks again for your help.

I will try your suggestions and see how things go.

Better try fuel from different station also.