GIGM08GT

I have a 99 Gt and I have this problem with a 'rattlling can' sound that happens when I put just a little extra pressure on the gas in first second and sometimes third(if I push it). Can;t figure out what it is. Sounds like its comming from the middle of the car. Can anyone help me out? Is this supposed to me normal?just got it back on the road after sitting a month.(stupid DMV) Thanks

Dan04COBRA

Get the car up in the air and start banging around and try to duplicate it. Sounds like a heat shield.

I'll let everyone else chime in with the real bad news if that isn't the problem..

GIGM08GT

what could this real bad news be? now you got me scared

GIGM08GT

If you think its one of the cats, that won;t be a prob on Thursday Finnaly gettin my H-pipe put on cause I don't have easy access to a lift.

01GTvertible

could be bad gas, or cheap gas. my 01 gt's valves make kind of a rattling sound when i get cheap and put low grade gas in it. sense your stang sat for a while, this could be the problem. id put fuel treatment in it, and run the tank down and fill er up with high octane gas.

Acer2428

SAME THING HERE!!!!!!!!!!!!!!!!!!

I finally said F it and brought it into the dealership...They thought it might either be:

A) Bad Cat (If it is, Magnaflow employees should sleep w/ one eye open)
B)Broken/chipped flex plate

Is your car an auto? I thought maybe mine was bad gas, but 1/4 tanks of 94 octane didn't help.

98cobrasvt

Fuel injector cleaner or it may be the a/c vents rattling like mine...

jdaniel

I didnt have that problem till I got the X pipe and I assumed it came with the pipe. Its really mild and its only there when im on it really hard. Other than that it has the deep tone of magnaflows.

pichinco

If it's really coming from the middle of the car, versus the engine, there isn't a whole lot to worry about. It's something loose. Heat sheild, exhaust, etc. If your having exhaust work done, have the guy look around while he's under there and look for something obvious. If you still have the same thing after Thursday...make SURE it's not the engine.

Pre-ignition knock is caused (as others have said) by cheap gas, too low octane, dirty injectors, dirty fuel filter, or dirty fuel system in general, contaminated MAF, mis-gapped plugs, etc. Beyond that you gotta dig pretty deep.