Sorry I'm starting a new thread on an existing subject, but I couldn't find one that already existed. I have a 2002 Trans Am LS1 that developed a LOUD/VIOLENT knocking noise over night. When I cut it off one evening it was fine, next.morning THIS out of the blue. Car wasn't ran hard and is all stock with 56K on it. I ran a diagnostic on the computer and it is saying misfire on cylinders 5&7. We cur the filter in half at the machine shop and found no trash in it, or the oil drained. I replaced the coil packs on 5&7, still no luck. Some PLEASE for the live of GOD point me in the right direction here. I'll include a link of a yTube video of what I'm talking about. Thanks in Advance fellas.... i just really want to get this beast back on the road, she's been sitting for a year 😞dum


-Mike

 

If it's been sitting for that long, I'd almost say collapsed lifter. Definitely sounds top end though.

 

Hard to tell but something is rattling around in there.. sounds valve train related to me(lifters,pushrods,springs, valves, etc), I wouldn't run it anymore either way. Probably will need to start pulling it apart. Have you looked at 5 and 7 spark plugs to see if they are damaged? Maybe others will chime in and help pinpoint it. That's more noise than I expected.

 

Check your plugs, but I'm guessing a rocker arm.

 

Weeble, it's been sitting that long because of the problem... It was running fine one day and then the next morning I went to start it this is what I found. It's not like it broke under high RPM or anything, it was a night to day thing, I don't know what happened.

 

I've pulled the valve covers and check the springs for NE hairline cracks and checked the push rods and Rockers to make sure everything was intact. Everything looked normal from that side of the head. I'm hoping that if I pulled the head off I will find a collapsed lifter or two comma but I was thinking that if it was a collapsed lifter the tension on the pushrods/ rocker arm wouldn't be so tight. I figured that a collapsed lifter would put some slack in the push rod where it seats in the rocker arm. Thanks for the replies so far guys, keep them coming. I really need to get this Beast back on the road, I think I've started to develop separation anxiety LOL

 

Ah understood.

 

Any other idea's? Does it sound bottom end ?

 

I'm not expert, but that doesn't sound bottom end to me. Do you have a mechanics stethoscope? You could try and pinpoint the cylinder/location of the noise and go from there.

In either case it's gonna need the heads pulled off most likely, I'd start with that and check things out.

 

Sounds similar to this... https://ls1tech.com/forums/generatio...bad-knock.html

Doesn't have a solid sound like the bottom end. I'm betting it's a rocker arm or lifter like others have stated.