when i drive my 97 blazer for 30+ mins and i get to a complete stop, then when i give it gas it makes a rattle sound for about 3 seconds then it stops.

i thought it could of been my exhaust leak but if it was it would rattle all the time. it only happens when the engine comes to idle and then revs

any ideas??

 

These things apparently have an issue with the balance shaft rattling when starting from a stop. Happens from about 1600 to 2500 RPM. GM knows and has come up with a fix. But the fix may not be permanent. Is it making your knock sensor go nuts?

 

yeah it happens at the same rpm everytime, but it seems to only happen around 1400 - 1500 and stops when above 1500, but no it isnt throwing any codes. so i aint sure. but it runs great and it only happens when i drive for really long. but it still has plenty of power

 

I bet you cat converter is rattling.

 

This.

Always check the cheapest option first. After your truck is cooled off, crawl under and see if the heat shield on your cat is loose.

 

While you are under there with the cat cooled off, knock on it and make sure the pellets inside arent rattling around(failed cat)

 

i checked the cat and it seemed fine. everything was nice and snug

 

The balance shaft is a common issue. Mine does it under load and causes the knock sensors to retard the timing.

 

thanks everyone but turns out it is the cat's heat sheild, only does it when it gets good n hot though

 

Thanks for your post. Your the first one I have heard that explained my engine rattle problem for the last 60,000 miles+. I emailed you wanting any other info you have about this issue. Where is the balance shaft located?
Thanks a bunch for your post.