1.8T Engine "Clatter"/Rattle

[Passatman]

Hi guys!

My Passat 1.8T's engine has had this noise since I got the car, from used, 2 years ago.
I hear a sort of a clatter/rattle when I blip the throttle.....
(First I thought the sound was linked to the turbo as it goes away once the engine is fully warm or the turbo is boosting, or revs are higher) .
However this seems to not be the case.
The sound seems to be coming from the rear of the engine where I see a lot of hoses and a vacumn component or two.
Can anyone shed some light?

Also, have just replaced the MAF as it had failed. Now when I start the car from cold the idling sits at just above 1000 rpm for about a minute and then drops down to the right level of about 800rpm.
Also, since the new MAF under light throttle the car seems to hold back at about 2,500 rpm and then pulls well. (Does not do this under medium to heavy throttle).
Car has Usolute chip and freeflow exhaust.

 

[madvw]

when was the car last serviced, what oil are you using, and how many miles has it done?

the cold idle you describe is perfectly normal for a cold car. as the car warms up, the idle speed drops to normal.

as for the holding back, it's most likely to be due to the remap. There are loads of different maps according to the load requested. If it was a general problem i guess it would always hesitate at 2.5k revs.

 

[Passatman]

Hi there and thanks for the reply

Car has done 140,000 km, has Castrol Synthetic....fairly recent service but not sure when fuel filter was replaced.
I did not mention that it sometimes holds back a bit at higher revs too, and did not do this before replacing the MAF so certainly not due to mapping as it has always been very driveable in town.....

Puzzled!

 

[madvw]

Is is more of a tappety rattle? Possible an oil starvation problem (pump, pickup, strainer, channels?)

 

[Passatman]

Hi (Like the name, am a VW nut of note!

Nope, the noise seems to be coming from the vicinity of the the vacumn pump (round silver item, looks like old fashioned mechanical type fuel pump) mounted at the rear of the engine (rear being opposite end to drive belts side).

Regarding the holding back, looks like the Coolant Temp. Sensor is busted...

Cheers

 

[madvw]

I could be wrong, but i think it's perfectly normal for that to tick.. If its what im thinking it is, it's part of the charcoal filter system for recycling petrol vapour..

 

[Passatman]

.as far as I can make out it adds oxygen to the exhaust gas just after turbo, before cat so that more of the exhaust gas can be burnt off to reduce emissions.......the rattle bugs me though cos when you pull away it sounds like I have tin cans attached to the rear bumper......just when it's cold though.....

How do you enjoy your S3? They are very quick....

 

[madvw]

still sounds like the charcoal filter to me, just my understanding of what it does is obviously wrong... well worth getting another opinion.. ...anyone?

S3 is great to drive. It's quick, but i's not fast, which is a bit of a dissapointment, but it's comfy enough to make up for that.