Afternoon clanking noise

[myblkgt02]

I have a strange noise that I am trying to identify before I got to a shop.

First off, I have a 2002 GT (63k miles) with a K&N FIPK and Magnaflow catback exhaust.

The noise only happens on the way home from work. As I get on the highway, I have recently noticed a brief clanking sound when I am in either 4th or 5th gear while in low rpm (2100) or when I push on the gas hard while in low rpm. Once the rpm's increase, the noise goes away. I can't tell where the noise it coming from, it just sounds like it's coming from the bowles of the engine bay.

When I get home, I have parked the car, opened the hood and rev the engine and the noise doesn't happen. It appears to only happen while the car is moving.

I haven't found anything loose in the engine bay except there is some slack in the throttle cable, is this normal?

Any ideas?

 

[Nater]

Does it sound like it's coming from the front or back? If the back, then the tips on your exhaust are loose. The hangers for the tips are quite long and you may be able to get by with chopping a bit of metal off. Also make sure that the pipes are not hitting any part of the frame, suspension or tank cover.
I do note that you said it possibly is coming from the engine bay. Try going to a higher octane fuel. It could be that your car is having predetonation. I have not heard what it sounds like but have read it could be like the metal ball in a spray can when you shake it.

 

[myblkgt02]

The noise is definitely coming from the front. My GT is na, noting that I do have a cold air kit. Can cold air kits cause detonation? I am going to put my car on ramp this weekend and take a closer look at everything.

My rear exhaust is tightened down very tight, so I doubt it's exhaust related.

And still wondering if some slack on the throttle cable is normal in an 02 GT?

 

[myblkgt02]

Update: Because I was concerned with potential detonation issues, I removed the F&N FIPK and the engine is running much better now. So far, I would say that the 'drivablility' of my stang has improved.

However, if in fact removing the CAI solves the issue, the I am frustrated. Adding a CAI to a 2002 GT shouldn't require tuning, correct?

 

[helty]

no, you dont need a tune with justa CAI. The K&N FIPK has been known to cause pinging in some stangs. It leans out your A/F ratio, which isnt good. Try running a higher octane fuel as mentioned above.

was the sound more like a rattle?

 

[myblkgt02]

Thanks for the reply. The sound could be called a rattle, why?

I think for now I am going to keep the CAI off. I am planning some big mods this summer, so I can live without it until then.

 

[helty]

well, pre-detonation sounds more like a rattle than a clank. If it sounds more like a real loud clank, it could be something else.

 

[cooter_11]

Yeah it sounds to me like you're pinging. I'd run a higher octane fuel.

 

[myblkgt02]

For now I am going to keep the FIPK off and listen for the noise.

I don't want to pay for premium fuel with only a FIPK, but when I hopefully upgrade to a new VT stroker crate motor and Kenne Bell this summer - I'll have no issues with paying for premium.

Also, I noticed that my exhaust sounds smoother without the FIPK - no more rumbling when slowing down. This is also what makes me really think the FIPK was causing the issue.

While I am dissappointed that I took the FIPK off, I did put in a K&N filter and removed the air box silencer, so hopefully I have increased air flow.

 

[the98stang]

Do a quick compression test just to make sure your engine is holding good pressure...

That will verify whether the engine has pinging/detonation versus rod knock.

 

[trinity_gt]

If you still hear a "clanking" noise -- as opposed to the sound akin to shaking a can of marbles that spark knock produces -- check the heatshields around the catalytic converters.

FWIW, an FIPK-II on my 02 GT hasn't caused any noises except increased intake roar at WOT.