knock after car warms up (intake manifold problem)
 

just picked up a 2007 ms3 yesterday. I noticed after driving home that the car had a slight knock but only at idle once warmed up. I came to the conclusion that it is most likely the vtcs came loose or is possibly stuck? Is this common? Also where is the vtcs solenoid located? Is the car okay to drive with this?
It sounds just like this video

Did you do a compression test before you bought it?

Negative, but the dealer had all the paperwork from when they did a compression test. The car is also completely unmodded. When it is cold it sounds perfect, just sometimes after it warms up I get the faint knocking sound.

1. That video is of a normal Mazda3, not an MS3.

2. Read.

3. There are plenty of parts websites that would show you where the Variable Tumble Control Shutter (VTCS) solenoid is, and you'd know this if you had looked around.

4. Here's your freebie. The VTCS solenoid is between runners 2 and 3 of the intake manifold, attached to the vacuum block. You can see it, but you probably won't be able to access it without removing the intercooler. The actuator for the vtcs shutter itself is on the driver's side of the intake manifold, and it has a light-green top half. I would've thought you'd see a CEL if you had something wrong with either of these parts, fyi.

@Raider; are these the same person? I smell troll

I understand it's a regular mazda 3. I've read the speed3's can have this issue aswell. And no cel... Thanks for the info

Nope.

Alright guys sorry if I posted wrong or asked a stupid question. Not a troll, just a new ms3 owner who is looking for some insight. After searching more, I found this video of a speed6 who is experiencing the same sound as I am. Is this normal? http://m.youtube.com/watch?feature=y...&v=wNUjvlL64ug

Anyone?

Anyone else have this problem? I've been seeing several videos of people with speed3's that make this noise but still no answers. Any help would be appreciated.

Also sound goes away once revved past about 1200rpm. And runs absolutely perfect. And no clutch pulsating problems.

from my understanding mazda has a major problem with their im. pull the vacuum hose and see if it stops. if it does its the runners fail and needs replacing. but then again it could be something else. there is a video about fixing the runner valves

do some research.... thats always the first step

Idler valve? Vapor canister valve? Go to a car shop.

Thanks for the info guys. I've been searching for almost a month now with little to no straight forward answers. I'll pull the vacuum hose and see if it stops. I put a stethoscope up to the I.M and it definitely sounds like it's coming from there. Also I know it's not a rod knock or piston slap because it goes away with any revs