Rattle from engine under acceleration

Hi guys/gals,

I'm helping a friend out with her 99 3.4L tacoma...she was told that the engine needed replacing due to a thrown rod. I told her to not do anything until I looked at it. Checked it out lat night and the car started right up and idled just fine. No CEL, no weird noises...nothing.

When I gave it throttle, a rattling noise started coming from the block. It didn't seem like it was coming from the heads (valves) and I HIGHLY doubt a rod was thrown (I've heard what that sounds like).

I'm thinking one of two things and am looking for this great forums feedback:
1) loose spark plug
2) loose timing belt (bad tensioner or similar)

If it the timing belt which is loose and thus resonating or rattling off the timing cover...can I check this without having to take off the PS pump, radiator and AC compressor? Can I pull that top cover portion without touching anything else?

 

You should make a video and post it so that people can hear what it sounds like.

 

Can I check timing belt tension without having to fuss with the radiator?

 

have you read this thread?

http://www.tacomaworld.com/forum/1st-gen-tacomas/354399-engine-swap-hard-warm-starts.html

there is a video in it for an engine noise she was hearing to compare with yours, she also never had a CEL

 

If you remove the upper radiator hose from the engine side, you can then get the upper timing belt cover off by removing the 10mm bolts that hold it on.

Just curious if the motor is leaking any oil? Was it ran low on oil? If you look for posts by my username you'll find where I just swapped on a replacement 3.4L into a 2000 Tacoma. I posted up a video of the engine making a noise. You might want to compare.

Also run the engine for a 15-20 seconds and then check the oil. See if there are any metal particulates showing on the dip stick.