Ok a little background on my car...An '05 5AT Sedan, purchased in March (this year) and now has about 7400 miles.

Ok so I've noticed a rattle of some sort coming from either the engine area or under the vehicle somewhere...

Yes i know the G's are prone to the notirious rattle issues, some of which I'm currently doing battle with...but this is different. I'll try and explain as best I can. Maybe the gearheads out there can help me. The dealer claimed they couldn't reproduce the symptom.

Here are the instances where I can hear it the most...(windows down and no radio bumpin). So I'm at a stop light waiting to turn onto an on-ramp to the freeway (up hill). Right when you turn there are some nasty bumps so i slow down and after I pass them I step on the gas to get some speed...As the car starts picking up (right before it down shifts for more power) I can hear this rattle (kinda like metal on metal) coming from what seems to be the bottom of the car. Here's where I get stuck in the description...kinda like some valves clanking around.

Another instances is when i'm cruising along (lets say 40mph, on a level street) I step on it as the car kicks in the lower gear I can hear it and through out when the car is pushin it. The G picks up speed just fine, from what I can tell at least. The sound is not LOUD but I can certainly hear it when the sounds echoes from the parked cars or anything next to me.

Anyone experience anything like this or know what maybe the problem? I'm taking it back to the dealer sometime this week or next and I want to know what to tell them. Your help and tips are appreciated.

-Edgar

OH, and at one point thought it was engine knock or something but I fill up with premium gas all the time.

 

The first instance you described (turning a corner, hitting bumps + accelerating) sounds almost definitely like the ABS/VDC. It's amazingly noisy in this car and does sound like a very unhealthy mechanical sound.

The second noise you describe, however... rattling while accelerating in a straight line, is slightly more worrying. I think we need more info. How long does the sound last? Do you have to accelerate HARD or just accelerate at all? Any specific gear? Worse uphill? A certain rev range?

It could be something benign like an exhaust rattle or a small stone or rock in the wheel or brakes.

Do you hear any noise when reversing? A good way to get a better idea of the parameters around the noise are to go somewhere where you can drive next to a big wall. You'll hear the sound much better then.

 

Ok getting a bit more specific...

In my first example I hear the rattle/clank after I pass the bumbs (drive through them slow) and then step on the gas to pick up speed going up hill. Since i go through this up hill/bump sequence everyday after work it sucks to hear.

The sound lasts as long as it takes to get out of a low gear...seems like it does it in 2nd. For example on the instance of getting on the fwy and i clear the bumps I'm probably rolling through there at about 25...not sure what geat the 5AT is on though...maybe 2nd or maybe 3rd...anyway after I clear the bumps (going up hill) I step on the gas to gimme more speed and when it drops to the lower gear is when I hear the clank clank (2700-3500 rpms)...when it up-shifts I can no longer hear it.

I would say I'm not accelerating hard but I push it hard enough to gain speed pretty fast. I'm not mashing the throttle though. It definately does it worse going up hill, the engine strains more to pick up speed when going up hill.

This is the only time I hear the noise...when i'm on a street and there are cars next to me or on the fwy onramp where there are bushes/shrubs.

I haven't heard any noises while reversing, then again I haven't reversed going real fast. When i first heard the noise i though maybe my exhaust is lose.

Thanks for the help so far...

 

Well now you've described that first instance differently, I'm not so sure it is the VDC. They do both sound like the same issue.

I think there was a TSB on the 03s or 04s for a clunking transmission like this but I don't think it was ever a problem on the 05s. Can anyone remember the details on the tranny 'clunk'?

 

I can't feel any clunks I just hear the rattling. The car picks up power just fine just that there's some rattling going on under there.

To sum it up and put it in simpler terms...I hear this rattle/clank noise when i press the throttle enough to make the car accelerate and catch the lower gear...This noise is especially louder when going up a hill...obviously because the car needs to work harder to get it going up the hill...hope that clears it up a bit. I don't feel anything BUT I do hear something going on. The tranny shifts with no noise or roughness to it.

 

At first I thought you might be pinging... but you said you use 91 grade fuel… if it is a pinging issue, try a different brand fuel (I know flamers will cringe, but try it) or try running a colder spark plug. The dealer should be able to diagnose on a test drive (don’t let them try to recreate just by revving the engine).

Just my .02

 

Yeah I use 91 octaine. I try and stick to one or two fuel types...(Chevron/Shell) occasionaly i do put another brand but always Premium.

What I'm definately going to do is take the service advisor or mechanic on a ride and reproduce the problem for them. BUT if anyone has an idea of what this could be, oh please chime in!! Thanks everyone!!

 

Sounds like a loose heat shield. If the rattling gets worse at higher engine RPMs, you'd expect anything loose to start vibrating. Do you remember hitting anything or bottoming out recently? It should be pretty easy to find the problem and fix it. BTW, I wouldn't read too much into the fact that the dealer couldn't find the problem. I doubt they put much effort into finding the cause of your rattle.

 

hmmm lose heat shield ehh...ok I'll jot that one down. That i recal I have never bottomed out or hit anything. Unless the wife did but she generally drives like a granny.

Where is the heat shield at anyway? are we talking about under the car or in the engine bay somewhere?

 

There are several heat shields. I can't name them all but you can expect to find one near the catalytic converter (which radiate a lot of heat).

 

oh I see...cool I'll keep that in mind. Thanks!

 

If I understand the problem correctly it normally happens during hard acceleration under load.... seems to me that if something was loose it would rattle more often/consistant. I'm no expert, just my opinion.

 

YES you understand it completely...during hard acceleration under load...Maybe it just makes more noise when i accelerate? hmm who knows.

I'm at a loss...I'm outta here for now and I'm going to play around with the noise to see if i can reproduce it differently.

 

I dunno... seems high likelihood of pinging to me - but from written description it’s obviously impossible to know. I think you are doing the right thing. Isolate the issue as much as you can then take it to dealer and tell them your findings. Too many people say "I have this problem (fill in the blank) what is it". If you are armed with specifics when you go to the dealer, you will save a **** load of time and frustration.

Good luck with you detection and solution.

 

yeah like you said go armed with facts/issues...I'm writing down all I note and if i have to take a ride with the service advisor or maybe even the tech who will work on the car...i'll keep you all updated.