Chasing problems and niw this? - 2000 Sierra

[Blue'72]

Hi friends, I guess it's been a few years, but anything I've needed help with thus far has been answered by searching this great site.

So I bought a used Silverado, GMC actually, to replace my Dodge RAM that didn't fit the Bill because of it being, a Dodge RAM.. Well my 225k mile new truck needed a fuel reg and iac motor for starters. It ran great until it started randomly misfiring, but ran good most of the time.

Took it for a dump run and it was running bad with the cel flashing the majority of the trip. Came home, parked in the driveway and moved the wife's car out of the way so I could get it in the garage, but the truck wouldn't restart when I was ready to pull it in. Finally got it running enough to pull it in before it died, and then replaced the fuel filter. Tried restarting it and it sounded like an old cheapie rebuilt starter trying to start an old sbc but kept catching and grinding. Still wouldn't start and I thought the pump was bad, even though the old filter was plugged.. Starter still sounded bad.. Last night I determined that the pump was good, and today I removed plugs and they were all covered with fuel. Turned it over without plugs and starter locked up. Finally realized that the short tab on the starter was broke off, so I went and got a new starter. The motor sounds horrible when it runs now. Luke something mettalic is rattling around in it. Drained some oil and it's clean. Checked the inspection hole in bellhousing and behind the plastic cover for starter, and everything looks fine. I'm at a loss because it doesn't sound like a rod, but wondering if a valve dropped??

I'm sorry for the long read. But if anyone has any ideas, I'd like to hear them. Btw, I did remove the socket and ratchet from the harmonic balancer...I'll try posting a video of it. I can't stand to run it mire than about a second because it's that horrid..

[Blue'72]

hrttps://youtu.be/KqM5Qrccudc

[GM-power]

Well if your starter was grinding and going crazy you may want to inspect the flex plate itself. Your link isn't complete or something is wrong with it.

[Blue'72]

I keep thinking it's coming from down there, but I inched it all the way around through the inspection hole and everything looked great. I can't find anything loose in the bellhousing that I could feel..

[GM-power]

If you could fix the link it would help so we can hear what your talking about. No cracks in the center of the plate near the bolts? Get part of a hose or a stethoscope and listen around while it runs to help narrow the area down.

[Blue'72]

Hopefully this link works.

https://youtu.be/fUHf-Sr4lmo

[Blue'72]

I hope the link to my video works now. Here's an update. I took the ignition and fuel pump relay out again and had my wife turn it over while I looked at the flexplate through the hole and behind the plastic starter cover. Looked fine, so I watched the top of the motor while she cranked it and everything looked fine. I put the ignition relay back in and had her start it with the remaining fuel in the rails and it sounded like the noise was coming from up top. I wanted to rule out any acccesory noise so I took the serp belt off then cranked it. It immediately made a huge bang and smoke was everywhere. I see that it blew the valve cover gaskets out, litterally out, and there was plenty of smoke coming from underneath as well, so I suspect maybe the pan gaskets blew out as well.? I'm going to pull it apart now, but I suspect I'll be needing a new motor...

[GM-power]

It sounds more external than anything. It didn't make that sound prior to starter replacement, is that correct?

[Blue'72]

It did make that sound just prior to the starter replacement. That's what lead me underneath when I noticed the broken starter. I thought the starter was making the noise, but realized that was in addition to it. Now that every gasket has blown out, I'll be pulling valve covers for starters to see if I can find out what's happened. Cannot wrap my mind around this..

[Blue'72]

This morning when I was discussing this problem with my brother, an idea popped into my head. I mentioned that when the light flashes, it can damage the... And then it hit me. That horrible sound sure did sound like a chunk of the cat rattling around, and it makes sense now why when I turned the motor over without the ignition relay, it didn't make any noise. Only when it was running. Why the starter broke is still a mystery..

Could it be that the chunk of cat had ended up plugging the pipe causing the motor to backfire back through the intake?? I mean, it literally blew out the rubber gaskets in the valve covers.

I really hope there's no motor damage!!

I still plan on pulling the heads and checking everything out as long as I'm at this point.

[truckdude239]

Im thinking you have engine problems if you poped gaskets....

[Boog]

It sounds like too much gas in the cylinders and in the crankcase when the ignition lit and boom! Possibly due to faulty fuel pressure regulator.
The noise it was making before the boom, i dont know.

[kev63rod]

i would pull the valve covers and see if you can wiggle any of your rockers, especially your exhaust valves. i had the same thing happen to my 6.0. lifter when to pot and wasnt opening the valve very far at all. sounded like something metalic in the motor and of course was sending all the pressure back into the motor. (could blow gaskets)

[Blue'72]

Here's an update. Thanks to all for the advice thus far! For some reason I'm having problems uploading pics into photobucket..

I pulled the pass side head and found #6 piston to be cracked all to , missing the skirting, and rings all bent up. The cyl wall didn't look too bad considering that the rod was flopping around in there. I'll keep that motor for future use. (maybe)

I found a motor with 144k that I heard run, but didn't do any compression testing or anything like that.. I'm really nervous and hoping it all works out good! The shop that sold me the motor is swapping it into my truck so I don't have to deal with it right now.

They got it in and running, but it's still got a random misfire. They didn't use any of the fuel or ignition off the old motor because it's all sitting in my garage at home.

[clinebarger]

Did the shop perform a "Cam-Crank" relearn procedure?
Does your truck have a really loud exhaust?
Hopefully its not a Cam-Lifter issues....
Does it have new plugs & wires?

[Blue'72]

Originally Posted by clinebarger

Did the shop perform a "Cam-Crank" relearn procedure?
Does your truck have a really loud exhaust?
Hopefully its not a Cam-Lifter issues....
Does it have new plugs & wires?

This shop does a lot of these LS motors, but I'll find out if they did the relearn procedure.

Exhaust isn't very loud at all.

New NGK plugs and new wires. They did tell me that these motors work best with AC iridium plugs.