2002 LS v8. Popped durring starting and won't stay running

[gopaperless]

I drove the car yesterday with no issues. I went out this afternoon to drive it and, when I turned the key, it made a sound under the hood like a small backfire (it didn't start). I turned the key again. It started and surged for a half of a second and died. The sounds the engine made during the "surge" didn't sound normal. It sounded like a call with a hole in the muffler. I tried again an hour later and same thing. It sometimes makes a "popping" or small backfire noise while turning over. Any thoughts??? I have spent too much on this car over the last few months and really don't want to spend any more. If its an easy and cheap fix, ok.

Thanks for the help...

 

[joegr]

I would certainly stop trying to start it. Each time you do, you may be doing more and more damage to it.

I'm sure there are several possibilities here, but these are the two that come first to my mind.

1. You may have jumped time on one of your cams. If so, every time you turn the key to start, you risk doing major damage as valves may hit pistons. The way to find out if this is a timing problem is to remove the valve covers and inspect the timing tensioners and chains. If it looks good, then turn the crankshaft by hand to see if you can get all the cam flats to line up. If you can't, then there's your problem.

2. Perhaps a backfire blew the end cap off of the intake manifold. Open the hood and have a look. If it has, then you probably will have to replace the intake manifold.

 

[gopaperless]

Thanks for the info joegr. Where would the cap be located? If its on another post, I can look it up. The odd thing is the sound. Its usually a quiet running car but it sounds like 4 cylinder car with a hole in the muffler. Its not that loud but noticeably louder than usual. I could see your 2nd option affecting the sound but would the first one show that symptom as well?

 

[FDR]

If the spark happens with an intake valve open, sure it could

 

[gopaperless]

Just a followup. I checked the intake and the plastic disk on the back of the intake was laying loose. Looks like joegr nailed it with the 2nd option. Now to order a new (or used) intake manifold and replace it. It doesn't look too difficult and I'm sure there is a good post that will walk me through the process.

Thanks all...

 

[joegr]

Next question, why did it backfire?

 

[Telco]

I mention this as something for gopaperless to investigate before restarting his engine.

The engine in my Silverado backfired, then immediately sounded like there was a hole in the exhaust while I was running along about 75MPH. Very shortly after that, the engine died. The consequent teardown showed that the #3 cylinder exhaust valve snapped. That valve knocked a hole in the side of the cylinder, which caused that one piston to stop while the rest of the engine was humming happily along at 2000RPM. Of course, VERY shortly after that it was no longer humming along happily at 2000RPM. In the case of my engine, it was my choice of a poor engine builder that caused my problem. A lighted fiber optic scope stuck into each cylinder through the spark plug hole would be the simplest way to check this. If the LS engine dropped a valve then you might be able to have an engine shop replace the valve. If you start and hope, you may be dropping several large to replace your engine like I did.

Busted head

Busted cylinder

Several grand later...

 

[gopaperless]

Update and "Its Fixed".
joegr was correct that the plastic plate on the back of the intake popped off. I finally got enough access that I could get the plate out and it looked like it had been glued back in by the previous owner (my opinion). I spent some time cleaning the old glue off and purchased JB Weld steel epoxy. It is rated up to 500 degrees. Ran a bead around the plate and stuck it back in there. 24 hours later I fired it right up and it has been running great for just over a week. I know it isn't the preferred fix and it could fail again but it saved me $250 for a used intake and several hours of work replacing it. I think the POP or backfire noise could have been the effects of it breaking loose.

Thank you everyone for your advice. I couldn't work on this car without you all.

 

[LS4me]

Update and "Its Fixed".
joegr was correct that the plastic plate on the back of the intake popped off. I finally got enough access that I could get the plate out and it looked like it had been glued back in by the previous owner (my opinion). I spent some time cleaning the old glue off and purchased JB Weld steel epoxy. It is rated up to 500 degrees. Ran a bead around the plate and stuck it back in there. 24 hours later I fired it right up and it has been running great for just over a week. I know it isn't the preferred fix and it could fail again but it saved me $250 for a used intake and several hours of work replacing it. I think the POP or backfire noise could have been the effects of it breaking loose.

Thank you everyone for your advice. I couldn't work on this car without you all.

I would be on the lookout for a suitable replacement. Try looking for a low mileage example at a salvage yard......