MOT Emissions Failure

[Jollus]

Hi my BBY 1.4 petrol 9n has failed on the emissions test. I recently replaced the cat converter and have also replaced the lambda sensors in the last few months. A friend plugged in their laptop to look at real data and confirmed that both lambdas are working as the graph lines were climbing up and down and not flat lining.
What could the problem be? Could it be that my spark plugs are due a change? One is seized and so I couldnt get them replaced in my last service. We are currently spraying it with WD40 to try and ease it out over time. Could it be this or could the problem be elsewhere? I am confused.

Thanks

[RUM4MO]

I think that the Lambda probe outputs will just "go up and down" - its due to the fuel controller allowing the car to run a bit rich then trimming it back to run a bit lean. I take it that you have checked the air filter element, also, I'd hope that you did buy proper VAG Lambda probes and cat? Was it the second cat that you changed and if so why did you change it, also what prompted the Lambda probe changes - where both identified as being faulty? I'm amazed that the plugs have seized in as I would have expected the seals on the coil bodies to keep any water/dirt out. What year and milage is your car as I changed the Polo plugs at 3 years/24,000 miles which is well within what they needed - but I just tried to play safe. Is your car using a lot of oil and do you only use it for short journeys?

[yorks GT TDI]

try a new coolant temp sensor mate

[Jollus]

Hi, Thanks for the tip. I havent had the time to get it checked out with work but will soon.

Unbelivably though my car threw a wobbler today! Since the service when the garage told me that a spark plug was seized, the car has run as normal as ever. It failed the emissions test last week as Co2 was on .800 when it should be .300. It also failed on the lambda reading but on live data the lambdas were working. I had a fault code come up to do with either the air flow mass meter, false air or a possible dirty throttle body. This came up months ago and the light never came on again.

Today however it started mis firing through all the gears as I was driving. I pulled in and restarted the car and it ran as normal. Suddenly the miss was back and it would go away. Ten minutes into the journey the oil light flashed red with a beep sound three times and the car cut out! The book for the car said to stop and call assistance as it is low oil pressure. I got the RAC to plug the laptop in which showed no faults at all. He said to change the spark plugs as they hadnt been done in the service and are old. So earlier today we got the seized plug out and its companions which were all in bad condition. It seems now that the misfire has gone since replacing the plugs. After starting the car though since changing the plugs it seems that the car over revs and it idles at just over 10,000 revs.

What the car was doing was running with the EPC and Exhaust emissions light on and the cooling fan would kick in. At that exact moment there would be no revs with the throttle peddle. We turned off and started again and the same thing was happening. I got the RAC to plug in again and it came up with MAP sensor. We cleared the fault and started the car and MAP sensor fault came straight back. He advised me to change MAP sensor tomorrow and see if the roughness stops. I have never experienced this sort of behaviour with a car before. It seems as though its automatically choking or something. Its like when you rev, the car revs a little bit more when you take your foot away. Also if you leave it sitting on idle it eventually starts chugging and struggling as though a flap is stuck closed on a valve or something.

Anyway if i dont get a reply I shall report back with how the car runs after I replace the MAP sensor.

[Jollus]

Damn! Couldnt get MAP sensor today its coming Tuesday. Does anyone think that it sounds like the MAP sensor is knackered? Or does it sound like the MAP sensor fault is coming up due to something else going wrong? Thanks

[RUM4MO]

How did you get on after changing the MAF - I thought that the MAF's performance could be checked by disconnecting its plug and that would force the ECU to use "nominal/average/typical" default values - if the running then improved then the finger would point to MAF - otherwise look elsewhere (I could be wrong thought!!).

[Jollus]

I see what you mean there. No I havent tried to disconnect the MAF but seeming the fault code was MAP sensor I disconnected that and the car was still rough running when idle. I changed the spark plugs and it passed the emissions on MOT. Happy days. Problem is its still cutting out randomly whilst driving. The rev counter suddenly drops to nothing then the car cuts out. If I restart it, it will run for a while and then cut out again. When it cuts out the red oil light flashes three times. I took it to a local garage but he thinks its because my ABS light is on and I need a new pump. However I have been aware of that for ages and the car has always run fine with the ABS light on. Its only in the last two days it has been cutting out. Just before it cuts out theres a loss of power, just like a little misfire or two.

Any suggestions as to what I should do? Obviously im searching for a new ABS pump cos its needed a change for months but surely the ABS pump isnt goona make the car cut out. Thanks

[jaydeezey]

I personally would give the throttle body a clean and replace the coolant temp sensor, both are cheap and easy to do and common problems across the VW range.