Okay, so I've asked my mechanic about this, and he says it's no problem, but just that my model year does this occasionally when cold. But, he's never actually heard it on my car because it has never actually happened in his presence... it always goes away when I get the car to him.
The problem is, as he calls it, piston slap. When my car is cold (and most disturbingly, sometimes after even long drives when it's nice and hot), it will sound like a diesel engine. This only happens between 1000 and 2500rpms. Any higher and the noise fades into the normal engine revving sound.
It really bothers me because it happens without predictability - hot or cold, but maybe more often when cold, and it's loud. Now, I've taken care of this car quite nicely since I bought it at 88,000 miles (maintenance-wise, tune-ups and all), and it's been making it for quite some time (but it didn't make it when I bought the car coincidentally).
Any help would be appreciated as to diagnosing what this noise is, and how it can be eliminated. Thanks!

Check out the timing belt tensioner pulley which is another sound just like piston slap. A lot of the H-4's have the slap, and in general it is alright, just alarming sometimes. Good luck. Brian

timing belt tensioner.
i love posting this.

it sounds a bit like a loud tapping, usually when cold and originates from the timing belt area.

So how do I adjust find the timing belt tensioner, let alone adjust it? As in, where can I find a diagram. Any suggestions on a good book? I don't like taking my car to the shop unless I have to.

The tensioner is non-adjustable, it is spring loaded I believe. As for it's location, behind the plastic belt cover/cam gear cover behind all the other drive belts. Brian

So can I replace the tension belt adjuster myself, or do I need to have a shop do it (like I would with the timing belt itself since that requires engine removal)?
Ooh, the really important question:
I had my 90,000 service at 94,000 at a local shop here in town. My car just hit 105000, and it has been making this sound for pretty much as long as I can remember. The 90,000 service includes replacement of the timing belt, so should they have replaced the timing belt tensioner as well? Is it possible that they just forgot? Oh, and for the record, I listened to the engine while revving it up into the RPM range where it's loudest (around 2K), and it sounds like it's coming from the front of the engine, not from one of the pistons. It's definitely from one of two sources: the front driver side piston, or the driver's side of the timing belt. Hope that helps, look forward to more input :)

Front drivers side is right where the hyd. timing belt tensioner is located. The shop probably should've changed it when the belt was done. If it was an indie shop, they might've skipped it, where a dealer likely woulda changed it. You can do this yourself, but it's 95% the same as changing the belt, FYI. I couldn't see the bill at a dealer giong past $200 if you had it done for you.


Hope this helps,
Jay Storm

Thanks Jay for the reassurance that a legitimate shop would have replaced the timing belt tensioner. The place I get my work done seems legitimate, and I have had a few references from friends of mine as to their credibility. I will be giving him a call early next week proposing the problem and the solution, and see what he says. He's a really cool guy, I just hope he doesn't say that the problem is piston slap even when it is the timing belt tensioner. Is there any way I can be SURE that it's the tensioner and not piston slap?