Odd Ticking Sound

Odd Ticking Sound - Help!

Hello. I've posted about this issue on other forums, but I'm trying to get as much input as possible.

I drive a 90 Mustang GT and recently it's been making an alarming ticking sound.

What happens is this:

As I approach 1700 RPM, more often than not a sound emerges from the engine that I can best equate to a woodpecker hard at work at putting a hole in a tree trunk. Once I round 2000 it immediately goes away. This can happen through all of the gears, and only during that small RPM range.

I thought it was knock at first, but I've heard other cars ping in the past and they tend to produce more of a hollow metallic sound than a tick. But, I'm still not ruling out that possibility entirely.

I haven't been able to duplicate the sound while in neutral. It only seems to occur while the car is in gear and accelerating. Also, it *only* occurs once the car has been warmed up and running for a few minutes. It does not happen at all when the car is cold or just recently started.

I've tried checking the timing, it's fine. I'm running 93 octane. I've tried unhooking the EGR sensor and plugging the vacuum. Nothing thus far has worked.

Thanks for any suggestions.

It only occurs under load. An exhaust leak would be noticeable by revving the motor in neutral, no?

And I don't think it's a matter of the sound dissapearing under the noise of the engine/exhaust. It either cuts out pretty obviously, or it gets much quieter once I hit 2000 RPMs.

Providing the oil pressure gauge is accurate of course, it's perfectly stable.

Took the car down some back roads so I could listen quietly and carefully. The noise *definitely* goes away after 2000 RPM. I was feathering the gas as gently as I could manage, and the sound vanishing at that point was completely apparent.

I'm starting to think it may be knocking now, because it does have a bit of a metallic clink to it. If so, what's next on the path to curing it? Like I said, timing is fine, 93 octane is in the tank, and the engine is completely stock.

Thanks.

Up.

Well the car is due for inspection soon, so I'll have them scratch their heads over it. Hopefully it lasts until then...