clockworks

The rattling sounds like a metal wand oscillating very rapidly, then being touched to a tin sheet metal. The sound happens for a fraction of a second and happens 2-3 times in rapid succession as I pass 3k RPM under somewhat heavy load. If I'm accelerating too quickly or too slowly, the rattling doesn't happen. It also doesn't happen when parked in neutral and revving the engine. I *think* the sound is coming from under my hood, but I'm not too keen on locating sounds. Also, I'm not sure, but I think I started noticing the sound after installing a K&N CAI. I've had multiple people check my install and they say it seems tight.

It's kinda hard to reproduce the rattling on demand. It just seems to happen only sometimes seemingly randomly, but always at 3k RPM with a moderate load.

My Stang was built the first week of July, so I don't think it has the "missing bolts" problem that was causing some rattling for other people.

Any ideas? Thanks.

05GT-O.C.D.

Does it sound like it could be your valves? It's hard to figure out what you're describing. But some ideas are, buy better fuel - try Mobil 93, if problem persists, ditch the CAI and see if the problem goes with it. Make sure there's nothing loose on your exhaust - heat shield, etc.

SuperCJ

I wonder if you are hearing detonation caused by an inappropriate fuel / air mixture. Did you reflash the computer when you installed the CAI? I hear that the 05 motor is very touchy when there is a diffrence in air intake over the stock programming.

I am researching which CAI system to buy and the ones that make real RWHP all require a reflash of the stock computer.

I'm no expert, just a thought to help you with a diagnosis.

Boomer

Except the MRT..
It makes good numbers...no tune required.

clockworks

Thanks for the ideas guys. I'm using Chevron 87 octane fuel, I'll try 93 octane next time. I need to find some time to swap the old airbox back on.

I don't think it's detonation though, but I have no idea what "pinging" sounds like. I mean, it's really hard to hear the rattling sometimes. Definitely can't hear it over the radio at med/low volumes. It's pretty hard to hear it when the windows are rolled up. I always imagined pinging is quite audible. People say, "you know it when you hear it."

The K&N CAI claims that no tune is required...that is why I got it.

lodom

Pinging sounds like a metalliac popping or ratteling noise and it goes away when you let off the gas, or reduce the load. It can be caused by over advanced timing and definately by a lean fuel mixture. It isn't necessarily that loud, and you probably won't hear it over the radio.

I'm in agreement that swapping the old airbox back in or going to 89 or higher octane will definately rule out the pinging. I'm leary of claims that aftermarket airboxes don't require a special tune given the S197's sensitive calibrations.

clockworks

The rattling I'm talking about only lasts a split second right when the needle passes 3k. Once it's past 3k, it doesn't do it anymore. No letting off the gas or reducing the load.

Still, I'm going to try 89 octane next tank.