02 Gt Random Knock

[Blazer974]

02 GT vert, manual trans.
Started up and let idle at work while talking with a few coworkers, all of a sudden a strange knock occurred and stopped. "What was that?" Almost like a rod knocking but it stopped. A few minutes later it did it again - knock clack knock - wtf was that... We opened the hood, revved it some, couldn't repeat the noise. Since last night it hasn't happened again, it's driving fine but it does sound like a pully making noise at idle just no knock clunk knock. Anyone have any experience? Wondering if maybe a main bearing is trying to go out with the sad part being a tuner is in the mail.

127,000 miles, only a CAI and Magnaflow Catback

 

[coletrickle46]

I have blown two of these 4.6 2v sohc motors and both times by over revving ( racing obviously lol ) and the clacking/knocking noise didn't appear rite away. It took a day or two and then progressively got worse/louder. Have you over revved it or been any where near over revving in the last few days?.. If you have then definitely the main bearings are scorched toasted!! If you haven't been racing, just messing around having fun then i'd try the idler pulley first and go from there. If you haven't been hard on it in a while then i wouldn't be super worried and over thinking things. Also how long has it been since last oil and oil filter change?.. What weight oil are you running??.. Good luck bro and lemme know what happeneds. What does it sound like it?.. Is it like a metal on metal type sound or more like a sewing machine sound??..

 

[Deleted member 38176]

Check your plugs. Make sure they are all tightened down. If it continues after that, then it could be valve chain guides. They wear out fast