MK7 2.4 TDCI 140BHP Diesel Knock

[Harry H]

I have a motorhome that's done 33500 mile that has a knock /rattle that starts at 2200RPM in 5th gear. It runs and sounds smooth up to 4th gear and not as pronounced in 6th gear. I have had the EGR delete and tune carried out by Vantuner as well as injector learn etc as well as injectors removed and checked but the noise is still there. What seems strange is that when the outside air temperature drops below 8 degrees the noise goes away. No mill light or fault codes are flagged up Once the outside air temp rises the noise returns. I was thinking of changing the MAF sensor. Any ideas please?

[knobby1]

Mine does exactly the same thing....only does it in 5th gear for some strange reason, very slight diesel knock/rattle @ ~2200-2300rpm, then goes away...runs exceptionally well otherwise. I think it may be a symptom of the remap..?? Mine never did it before the remap.

Lord Knobrot

[Harry H]

Did you get your remap at Vantuner? Also does yours run fine when outside temperature is below 8/9 degs? Seems very strange that it runs smooth in all other gears.

[knobby1]

Did you get your remap at Vantuner? Also does yours run fine when outside temperature is below 8/9 degs? Seems very strange that it runs smooth in all other gears.

Not a Vantuner map, it's a "Bluefin Map", happy with it though. I live in Brisbane Aus....and we rarely see temps in single figures, even in the middle of winter. As mentioned, it runs exceptionally well and gives great economy for a block of council flats being a LWB Hi roof...I always get ~8-8.5L/100km (which is ~34mpg)......so the best part of 1000km per tank.

Lord Knobrot

[Harry H]

OK thanks it sounds vey similar. May have something to do with the map, mine like yours runs fine and gives good fuel consumption, just strange and no one else seems to have heard of this happening.

[knobby1]

OK thanks it sounds vey similar. May have something to do with the map, mine like yours runs fine and gives good fuel consumption, just strange and no one else seems to have heard of this happening.

As I understand it, mapping is quite difficult to get perfect for every engine, each have their own "characteristics" at certain rpm's, loads etc...I tend to look at it as ...."it's a diesel, it's going to knock a bit no matter what you do".

Lord Knobrot

[loot]

No harm in doing the learns though

[knobby1]

No harm in doing the learns though

Aye...makes no difference to mine though, still does it.

Lord Knobrot

[Harry H]

Same here, had everything checked and learns done still the same.

[loot]

My van runs smooth smokes sometimes mind