richwen

Many thanks Ken - will see if I can check this too... Regards, Rich.

Hi Another thought occured to me along the lines of what the MOT tester suggested in his potential list of sensors/CAT......I think on a couple of occasions I may have overfilled the engine oil - could this clog up/wreck the cat? Just a thought.... Rich.

Many thanks for your thoughts - have looked inside flap motor + ECU as suggested by MicMac and its pretty coked in both and the end of the air pipe that plugs into flap motor - will de-coke these before I refit them. I may be barking the wrong tree with the sensors but I took the car for a drive with MAF plugged in and then out and couldn't notice any difference - it still hesitates going uphill/under heavy acceleration with occasional rough idle. Should I notice any difference? Maybe you can't tell that quickly given its been smoking for a while and therefore so coked. On paper I suppose it shouldn't be the MAF valve given I replaced the original with a recon Bosch one 50k ago but I imagine stranger things have happened! The point about my driving habits is probably valid as I do a lot of local stop/start travel. Regards, Rich. (sorry for the late response - as my neighbours understandably think I have no life working on the car till 1am, I'm going to bed!)

Hi I changed air filter about 14k ago. Will check as you have suggested soot build up in EGR. I doubt its EGR itself as I renewed this about 45k ago...Car has been smokey for a while as I struggled to get it through the last MOT and it only just passed even though I had all the high mileage injectors rebuilt! Many thanks for your reply... Rich.

Hi, I wondered if anyone can help. My Octavia mark2 1.9tdi 2005 failed MOT on excessive emissions (5.88 m-1 max should be 0.8 m-1). He suspected a sensor was at fault or maybe a clogged cat. I was getting (sometimes) hesitation then surging on hill climbs, occasional rough idle and black smoke (unsurprisingly!). I've cleaned the grounds in the engine bay and checked leads voltage supply and ground to both coolant temp sensors with a multimeter (both 5v and 019 continuity) , MAF (12v and 019 con. + 5v ref wire), MAP (5v and 019 con.) and fuel temp sensor (again 5v and 019 con.) which all seem fine. However, when I do a back probe on MAF black posn.5 signal wire (engine running) I get start reading of only 1.6v, increasing to 2.8v on acceleration. Does anyone know what the starting voltage should be? Same problem with MAP sensor. Apparently, voltage (from back probe on purple wire posn.4) should decrease the more vacuum is increased which it does from 1.91v to 0.73v but what is the normal range for my car? Same problem with the other test on the yellow IAT signal wire - with other makes of car on youtube, voltage should be a constant 4.8v - 5.2v - mine:- 2.7v?!? Sorry a bit longwinded but I'm no good at car electrics! Any help much appreciated or even where I should look to find these figures.Thanks, Rich.