Car Repair...

[AJDZee]

Anyone out there knowing a lot about car repair,

I hear a rattling from my car, started two weeks ago. (2008 Lancer, manual)

I know it's next to impossible to tell me exactly what's the problem over a forum, but maybe the following info could lead in the right direction:

1. Rattles only during acceleration, not while coasting
2. Rattles only when in gear, not while parked and giving some gas.
3. Haven't yet seen a change in fuel consumption/power ... although I'm watching it.

I ask because if at all possible I'd like to fix myself if not too big of a job, but I don't want to take it to a shop and get charged for diagnostics if I don't have to. (Points #1,2 suggest something drivetrain which means it's probably not a job I can do, unfortunately)

Any help is much appreciated, thanks!

[zataks]

Where is the rattle coming from?
Does it get louder when you apply more throttle or at different RPM ranges or is it constant?
How many miles on the car?
Did you have the car at this time last year; does the noise seem to come on only at certain ambient temperatures? 
Does it only happen when the car is cold? Or only warm? 
Have you recently started using the A/C?
Have you recently hit a serious bump/taken the car off normal tarmac?

[Greg]

If the rattle happens more when turning and less going straight, this would suggest a bad CV joint.  There are 4 of them, one at each end of each axle at the front. Usually the outer joints go bad first.  You can inspect them for rubber boot damage by turning the wheel out, then look at the rubber bellows that is the CV joint boot.  If it has a tear or is otherwise damaged, it can allow the usually black CV grease to escape and debris to enter, which ruins the joint.  Often CV joint grease will get flung onto the rocker panel from the grease leaking out, makes a mess.

Could also be an exhaust or engine mount issue, as the engine can move quite a bit under acceleration. 

Or, if there's an engine issue the rattle could be detonation (preignition) which can cause internal damage.  Is the check engine light on?  It's new enough that this should cause a code to be stored by the OBD system.

[AJDZee]

Good questions fellas,

The sound is definitely coming from the front of the car, can't tell if it's directly under the engine or to the side by a wheel.
The rattle gets a bit louder with more throttle (that being saod, it's not very loud. I can easily drown it out with radio)

I haven't tried accelerating AND turning, I'll check next time I drive!
The car just hit 60,000 miles
I had it last year at this time, the temperature doesn't seem to be a factor
Happens when car it cold or hot. Happens with A/C on and off,
Check engine light isn''t on.

One thing of note: over the winter I had a  plastic guard under my engine come loose, dragging on the road. (My theory is it got caught while backing out if a snow/ice bank I was plowed into, or a pothole I ran over...but it happened 3 months prior)

[zataks]

So hard to say.  I'd suggest crawling underneath and looking/poking/pulling/shaking things around where you had plastic fall off and see if you can find anything loose.

[Thegoblinchief]

CV joints are more of a knock knock knock sound. Turn the wheel all the way left and drive in a circle. Repeat to the right.

Faint rattling can also be exhaust pipe shields.

[greaper007]

It sounds like a heat shield or one of the underbody panels.    I can't think of too much else that simply rattles when it goes bad.     Get underneath and check the heat shield that goes between the body of the car and the exhaust pipe (should be a silver colored thin piece of half round insulation).     There might be several under your car.      These are fitted with simple push on type connectors (no bolts) and they'll occasionally get loose and make a rattling sound.

If you find this is the culprit, examine the fittings on the shield.    You'll occasionally have one of the fittings fall off which is why the shield is falling down.    If this is the case, I'd suggest going online or to your local dealership and buying a fitting directly from them.   Yes, it's more expensive than autozone, but I've had bad luck with the universal type fittings in the past and find that with things like this it's better to get a manufacturers fitting directly.

If it isn't the heat shield, take a look at the panels that go between the ground and the body.   Not sure what your car has, but my Volkswagen golf has one panel below the engine that occasionally falls off on me or gets loose.    My civic hybrid has one continuous body panel (for fuel efficiency).     Again, if you find a fitting is loose with one of these, get a manufacturers specific fastener.    I'll occasionally use zip ties on my golf, but they don't always work as well.