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Lambda probe/Oxygen sensor


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My V6 has been lacking performance for sometime now, have changed coil pack, Cat, plugs n leads and Maf, also cleaned out EGR valve and blocked it off, changed fuel and air filters only last year. Changed the MAF 3 times because of fault codes

1st MAF cheapy from ebay, still showing faults, sent back got full refund.

2nd MAF Bosch from motor factors, still showing faults, (after checking out the wiring), got it exchanged no questions asked.

Finally at last the 3rd was ok with no faults, but didnt make any difference to performance or lack of it, instead (3 months down the line) I was getting fault codes for the OXYGEN SENSOR.

Anyway after reading several posts about the OXYGEN SENSOR I thought I'd try disconnecting it, and yeh what a difference that made, much smoother and quite abit more poke but less MPG (connected 28ish mpg, disconnected 25ish mpg) by now I thought I was getting somewhere with the lack of power for the past 8 months, it just had to be the OXYGEN/LAMBDA sensor.

New Bosch sensor from the motor factors £66, put it in (reset the ECU) and went for a spin and MPG went up to about 29 but the lack of power was back.

:-(I'm so fed-up now I'm thinking of disconnecting it again just to get the power back and leaving it that way, is that ok to do so?

Oh yeh something else I nearly forgot to mention aswell was of more recent the tickover is jumping up and down abit but with the OXYGEN/LAMBDA sensor disconnected the tickover was quite stable. Its done 107k miles by the way.

I'v always been able to sort everything out myself up until now so I dont wanna give up and have to pay a garage to sort it out.

many thank for reading

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the temp sensor in the water housing on the front of the engine? that might be your fault is the lamba sensor is working as that has a huge part in the fueling of the engine, but its weird how the lamba been unpluged is improving the drive, i would most likely say you have a faulty maf or lamba sensor but if not try the coolent sensor i think its the blue one (get someone else to tell you if im right or wrong :-p) but yyea i bought one 5 months back and it was a 10er

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  • 4 months later...
  • 2 years later...

I had to replace the Lambda on pre cat bank one on the MK 4, with the faulty sensor the ECU defaulted to a standard fuelling pattern that gave poor performance and a high tickover, after having a complete mare of a time changing the most inaccessible item on the car (the other three were more prominent) I got it switched out and replaced, now tickover and throttle response are really good as are the emissions as it passed an MOT today with good low figures.

I also had some strange error codes as a result of low voltage, this might be worth checking.

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