Had the car put through a freindly mot - and it failed on the emissions. The car has not been de-catted. It passed the year before with no problems

My mechanic told me that hes certain its running on 3 and that it failed by miles - despite no power loss. So today, one by one I unplugged the coil packs - and everytime the iddle dropped. So this has confirmed its on all four.

So what could be the problem!? Im worried somethings wrong...

TY in advance

Tucker

 

Faulty o2 sensor perhaps?

Is she feeling lumpy lately, my car was having hiccups come mot time almost like a missfire yet all 4 coilpacks were brand new, threw in a new sensor problem solved.

 

could be mate yeah - and it has sounded a bit rough sometimes. The o2 sensor in the downpipe right? Not lamdba in the header?

 

What exactly did it fail on mate?
Co i'm guessing not Hc, if it is the Co then more likely the o2 sensor, i'd clean the air mass metre too with carb cleaner or brake cleaner just in case it is giving a false reading and running rich. If it failed on Hc then you have a problem with the burning of the fuel ie spark plug, coil pack, injector. Have you got your emmisions data from the test?
Dean

 

Dont have the print out mate - as I was at work so the mechanic took it to a friendly garage! Im not sure what it failed on but will prob have to find out.. If it was a coil pack or spark then would I get a drop in revs when unplugging the coilpack?

Is it safe to clean the MAF with carb/brake cleaner? It does run rich - which is also what led the mechanic to diagnose a mis-fire.

 

The o2 sensor is the lambda sensor so the one in your headers.

The one in the downpipe is the cat on fire sensor.

 

It's ok to clean it with those mentioned or if you are particular then use electrical contact cleaner. Let us know what it failed on and it will give us a better idea. A poor spark plug or injector can fail without a notice from disconnecting them.
Dean.

 

Mine only passes if its nice and warm (As in just taken round the block)