car just passed mot-exhaust emissions running rich..

[Jasikasisback]

ok i am stumped as to why the fuel mixture is running rich..i have changed the exhaust, injection flange mount (throttle body looks ok and plugs look ok), rocker cover gasket and breather/vacuum hoses...no idea why still running rich..

i was wondering if a clogged fuel filter could cause this problem.....and what other ideas people have..

it is causing lumpy idling when i stop...but ok in neutral...fuel economy is poor...

at least it passed the mot...no advisories...

[itavaltalainen]

any fault codes stored in ecu? which engine (code) is it?
maybe temp sensor?

[nolandubholmes]

Any air leaks ?? Vac leaks plus I'd get it checked for fault codes check some live data if poss and then go from there but as above if ur coolant temps giving a mad reading of freezing cold it will fuel too much

[mrsaunders]

maf? lambda? could be a number of things

[Jasikasisback]

temp needle works ok...at least it appears to be ok...no leaks that i can find...or that the MOT place noticed..

runs fine on the motorway...but very rich elsewhere...

no fault codes found last time i checked..but maybe should check again at my friends...

but for a 17 year old car...what can you expect?

[itavaltalainen]

temp needle working ok does not say anything, that uses a different sensor than ecu (albeit both sensors being in the same housing).
read temp with vag com to see if it's that.

[javalin]

yup +1, most common cause is faulty temp sensor.

[Jasikasisback]

temp needle working ok does not say anything, that uses a different sensor than ecu (albeit both sensors being in the same housing).
read temp with vag com to see if it's that.

Ive got the same engine as you do. Maybe you can send me a picture of where it is located or explain where it is?

[itavaltalainen]

Before replacing measure pins 1+3 and 2+4 at totally cold engine (leave over night) and when it's warm (when it shows 80 - as when speedo shows 90 its anywhere between 80 and 100) and compare values with the diagram.
The diagram covers only pins 1+3 but 2+4 should give similar response, just measured a spare one I have still from my old Golf. Resistance between pins 2 and 4 is approx half of what it is between 1 and 3.

Here's the image with location of sensor: