Changing Knock sensor on V6 - Alfa 156 - Alfa Romeo Forum
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Changing Knock sensor on V6 - Alfa 156


Send my baby to the dealers today to have it tested on the there computer. I thought i had problems with my Maf.

My car has been running af bit rich, and i have smell light smell of petrol when the engine is at idle. The Motor is running smoothly and has no problems taking revs an going 235 Km/H.

Without having any numbers, i also have the idea that fuel consumption has gone up.

The only thing that kept me wondering was the fact that he said that otherwise the engine was running fine?

The dealer told me that i need to change the knockingsensor, and that it has shown a fault on their computer.

How many knocking sensor's are their on the engine. I have been told it is the one under the air intakehose.

How difficuelt is the the swap, and do anybody know the excact location ?

Are there anything else i should change while down there ??

Best regards

From a fellow Alfisti from Denmark.
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(Post Link) post #2 of 5 Old 02-10-10 Thread Starter
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Bump.......... No ideas anyone.. I thought that a lot of alfatechs were on this board...
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There are two knock sensors. located in between the cylinder banks.

You can see the two black cables going of them.

To replace them the heads have to come off.

There is a water pipe going above them:

and with the heads on, you will not be able to access them:

Sensors should be about 50 EUR each, but the job is basically an engine rebuilt.

The sensor you mention, under the air intake hose, on the rear cylinder bank, close to throttle body that is cam position sensor.

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Originally Posted by gotcha View Post
To replace them the heads have to come off.
No they don't.

To replace either of them you just need to remove the thermostat and manifold pipe (after of course whipin off the inlet ducts as required.

But before you have any replaced, have them vacuum down in the area of the sensors as it could be a stone or something vibrating against the sensor but for it to be smelling rich I would say it's a lambda sensor at fault and not a knock, as those almost never fail.
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Agreed. Even if the knock sensor had failed it would not make the car run rich as it only affects the timing.
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