Noise under acceleration

[Moonman8]

When accelerating, there is a weird rattle-like noise coming from the front of the car. It sounds like an exhaust leak but it's coming the front. Plugs replaced yesterday, exhaust system has no leaks, stock airbox. Any suggestions? I was wondering if a sound like this could be caused by those screws holding on the butterflies inside the intake manifold for the VTCS system. I hear they can become loose, but would this cause a VERY noticeable rattle noise under heavy acceleration? Something with the butterflies themselves? Anybody else have this problem? Thanks.

 

[Mazda P5 driver]

When accelerating, there is a weird rattle-like noise coming from the front of the car. It sounds like an exhaust leak but it's coming the front. Plugs replaced yesterday, exhaust system has no leaks, stock airbox. Any suggestions? I was wondering if a sound like this could be caused by those screws holding on the butterflies inside the intake manifold for the VTCS system. I hear they can become loose, but would this cause a VERY noticeable rattle noise under heavy acceleration? Something with the butterflies themselves? Anybody else have this problem? Thanks.

I posted about this a month or so ago.

I haven't noticed any loss of power but can hear it. In neutral nothing..under load yes. I use 89 octane as well and tried a fuel cleaner. Still there.

 

[Moonman8]

Have you learned anything about what might be causing it? It's the same for me in that I don't hear it with neutral revving but only under heavy acceleration, which also makes it incredibly hard to diagnose. (braindead Sorry to hear that you have it, too.

 

[Mazda P5 driver]

Have you learned anything about what might be causing it? It's the same for me in that I don't hear it with neutral revving but only under heavy acceleration, which also makes it incredibly hard to diagnose. (braindead Sorry to hear that you have it, too.

Nope. Nothing. No CEL's or anything.

 

[16902]

Is it when the car is cold? Mine has always done that and I thought it could have something to do with the first cat.....but then again, what do I know? (braindead After it has warmed up, it no longer does it.

 

[Lord_Zath]

When accelerating, there is a weird rattle-like noise coming from the front of the car. It sounds like an exhaust leak but it's coming the front. Plugs replaced yesterday, exhaust system has no leaks, stock airbox. Any suggestions? I was wondering if a sound like this could be caused by those screws holding on the butterflies inside the intake manifold for the VTCS system. I hear they can become loose, but would this cause a VERY noticeable rattle noise under heavy acceleration? Something with the butterflies themselves? Anybody else have this problem? Thanks.

If it's a rattle noise, then I'd think it's the screws like you said. Take it to a dealer if it's under warranty asap. Driving with those things in the chamber is NOT a good idea.

Maybe it's also something rubbing against the master cylinder? Follow the intake and see if anything's loose going into it or something. There's plenty of sensors that could be off...

 

[Moonman8]

It is still under warranty, but it only does it when the car is warm and been driving for a while. I already know about the hesitation and loud cold starts but this is unrelated. It is definitely when its hot. I just don't want go through the PITA process of yanking the intake manifold to check the butterflies of VTCS system. Maybe I should just for the peace of mind. Thanks all.

 

[Moonman8]

I've had a couple of responses suggesting to check the heat shields but my thought on that was that the heat shield would rattle even while revving in neutral, correct? I haven't had a chance to get underneath the car or rip apart the intake manifold yet, I'm just trying to get some more information so I can check everything out. Thanks to all who have replied to these questions. If you have any more thoughts please post!

 

[Lord_Zath]

if under load and on stock motor mounts, the engine may shift forward, which could cause a different situation than if it was sitting at idle...

 

[vyse12012]

I had something like that before ...



when I was around 93-97 km/h , their was a metal noise coming from the front ... it wasn't the heat shield, and it wasn't the exhaust ... dunno where it was .. but when I got my new wheels, I didn't hear it anymore .. weirdo :S

 

[UtesFanRy]

When accelerating, there is a weird rattle-like noise coming from the front of the car. It sounds like an exhaust leak but it's coming the front. Plugs replaced yesterday, exhaust system has no leaks, stock airbox. Any suggestions? I was wondering if a sound like this could be caused by those screws holding on the butterflies inside the intake manifold for the VTCS system. I hear they can become loose, but would this cause a VERY noticeable rattle noise under heavy acceleration? Something with the butterflies themselves? Anybody else have this problem? Thanks.

Interesting...

Sounds like you and I have the same problem. I thought it was an exhaust leak caused by my broken front motor mount. I took the car to the dealer and had both AWR mounts (95's) installed, as well as some other stuff. The crappy thing is that the noise is still there. I also have new plugs, timing belt, drive belts, and checked by myself and an independent shop where I live to verify no exhaust leaks. Like yours, the noise is VERY noticable, and mostly under acceleration. The volume of the noise seems to be related to how heavy the acceleration is. It comes at about 2800 rpm and I can't hear it after about 3900 rpm. However, if I rev the car in neutral, I can hear the noise at the same RPM's, but it is MUCH MORE QUIET.

If anyone has any suggestions, thier help on this would be greatly appreciated.... I am taking the car back into my Mazda dealership in the morning to see what they can find... I'll post with the results...

 

[Moonman8]

At least it sounds like this is not an isolated incident. I'm going in to the dealer tomorrow as well. The difference with mine is that it doesn't do it at all in neutral, at any specific RPM. I only hear it when pushing half throttle or more in the lower gears (it gets loudest in 2nd, quieter in 3rd, and almost disappears in 4th). But it does seem to be related to how hard I'm accelerating (how open the throttle is). It's louder if I'm accelerating harder. That's why I think it might have something to do with the air/intake system or maybe even the throttle body specifically. I've heard things about the VTCS butterfly valve screws coming loose but I've since learned that they stay open if the engine is warm, and I only hear the noise when it's warm. But at the same time, a lot of air flowing through the intake manifold (like at full throttle), would agitate these screws nonetheless. Post something if anyone learns anything new. Thanks.

 

[Moonman8]

Has anyone investigated the synchros or related tranny items with this metallic noise? I just read over my last post here and had a thought as to whether or not the tranny is to blame, since the sound is louder in 2nd and starts to go away as I upshift.

 

[hopeful]

i noticed this noise today too, i really think its related to the tranny because of what the car went through the other day (tracking) gonna try running Redline MT-90, will post results.

 

[SkinnyJoint]

I Have This Problem As Well. As Far As I Can Tell It Is The Screws. But Like You Said Mine Is Around 2800 Rpm And In 1st And Second Its The Loudest While 3rd And 4th I Dont Hear It. And I Never Hear Anything In Nuetral.
My Car Is Not Under Warranty Though And How Much Would This Job Cost? And How Would They Be Able To Know For Sure That It Is The Screws?
Havent Noticed Loss Of Power At All. What Are The Long Term Effects Of This?

 

[Lord_Zath]

only way to know if it's the screws is to look at the butterfly and see if they are missing, and check the cylinders to see if there are any foreign objects in it...

 

[SkinnyJoint]

so i would have to rip off the valve cover gasket to check the butterflys?

 

[Kooldino]

if under load and on stock motor mounts, the engine may shift forward, which could cause a different situation than if it was sitting at idle...

Actually, wouldn't it shift back?

 

[Lord_Zath]

Actually, wouldn't it shift back?

(shrug) just a thought, but I do remember seeing a video of Pat's mp3 on the dyno and the engine didn't shift back until he let off the accelerator...

 

[Kooldino]

You might be right.