ok so I have a 2001 blazer with about 400 miles on a rebuilt engine. Started popping p0300 code so I took it to a local garage to have a relearn done. Ses light was on and the truck was running ok. When I went to pick it up the mechanic told me he didn't think a relearn would help. He said he would address the knocking problom before he would worry about the service engine light. Well when I dropped it off it wasn't knocking. Anyway he said it only done it at idle and when you put it in gear and held the break and give it the gas the knocking would stop and he thought that the torque converter bolts may be lose. Does this sound like a likely problem to you guys. Just seems odd the noise stops. Never seen this before. Any ideas??

 

possible since the engine was just replaced. ive seen flex plates crack and sound just like a rod knock. what sucks is on these s10s you have to pull the starter to get at those bolts. i think you might have a little rubber gromet access at the bottom of the transmission but dont think you can see the bolts, might be able to see if the flex plate is cracked.

when mine cracked years ago it was due to the actual transmission itself coming loose off the engine so check those to while your under there