V8er

iTrader: (2)

Hey guys,

My LS1 has a serious problem and I need your help! Let me know if this should be posted in a different section.

After a casual drive to work below 3000rpm I parked my car for the day. I went out after work and as soon as the engine started it was only running on two or three cylinders! I hooked up a scanner and there are no bad codes that would indicate the car is hardly running. The gauge was showing good oil pressure so I tried to run the car for about a minute but it didn't get any better so I just left it parked

What could have happened on start up to cause this? Can the timing chain ever skip a few teeth? Is there a cam or crank sensor that could cause all the timing to go way out of sync? Can the PCM program get messed up and require a reflash?

The engine is a freshly built (2k miles) 347 with forged pistons, AFR 205s, Comp lifters, Rollmaster dual chain, GMPP chain guide, high flow oil pump and all the other usual goodies. Every part was brand new and assembled to spec.

Any help would be appreciated

patriotformula

iTrader: (28)

check the oil... make sure you dont have a bad head gasketleak that has caused a hydroloc type of situation (less severe obviously because yours is still running). The reason I say that is you have a new shortblock but was the block decked and stuff? Im sure theres a million things it COULD be.

V8er

iTrader: (2)

My coolant and oil levels are both perfect.

Anyone else have some ideas for me

AintQik

iTrader: (3)

Only well to tell is to tear it down. Mine made a similiar noise when I broke the roller off one of the lifters. Had good oil pressure.

5.3LJimmy

iTrader: (10)

Starter not disengaging from the flywheel? It's odd that you drove to work w/ no problems and as soon as it cranked up it was making noise. Could be a bad starter.

V8er

iTrader: (2)

Yeah, not really what I want to do!

Did yours break at start up/idle or when you were driving?

AintQik

iTrader: (3)

I stopped to go to the bathroom on the side of the road. Got back in then bang. I thought a farmer or somebody shot the car. It was when I started it back up.

I like the starter suggestion and hope like hell that's all it is.

V8er

iTrader: (2)

Did your engine have Comp lifters? Did it damage a bunch of other internal stuff or were you able to just replace the lifters?

j-dubya

x2. check out your starter for starters ( no pun intended )

jeremy

V8er

iTrader: (2)

Guys, I just tried the car again and the starter isn't it. The car is clearly not firing on all 8 cylinders --- actually I would say more like 2 or 3 cylinders.

It is looking more and more like the heads need to come off unless someone can think of another good reason why it would be mising this badly?

Asmodeus

with such low miles on it it could just be a part failure.. no real explanation other than it just failed.

V8er

iTrader: (2)

As of right now I'd say this is the best explanation but it is surprising that I am the only guy this has happened to

If a lifter broke would it have damaged any other part(s) of the engine or should I be able to replace the lifters and go?

Has anyone ever heard of a timing chain skipping a few teeth and causing this kind of problem? The reason I ask is because it really feels like the engine is running on about 3 cylinders, not something I would expect to hear and feel if one of the lifters broke!

Grimes

iTrader: (3)

I have never ever heard of a timing chain skipping teeth. Only breaking. Skipping teeth and staying on would be almost impossible.

V8er

iTrader: (2)

Fair enough - I just don't see how a lifter breaking could cause the entire engine to miss and hardly run. Wouldn't it feel similar to removing one spark plug wire if it was one broken lifter or rocker or valve spring? Whatever happened to my engine has affected how the whole engine runs!

V8er

iTrader: (2)

Anyone else

Asmodeus

I''d take it to a shop. One of the sponsors here if you are close enough and have them give you their opinion. It's very hard to diagnose something like that without seeing the car. And a morning bump for you.

and yes, I have heard of a chain jumping before, and if it did, you could have valves hitting pistons.

5ltrBetr

iTrader: (3)

Sorry to hear about your troubles. I would suggest one of four things and in order of its easiness to check. Broken rocker, broken pushrod, broken or spun around lifter, broken or loosened rod bolt. Take off the valve covers and check the rockers and pushrods. No dice, remove the heads and check the lifters. If a lifter has broken or spun around, it will make constant bad noises as it begins to desinigrate your cam lobe. Last, you'll have to pull the motor and check rod bolts. You cannot ignore it for sure. If it is a knocking sound like you describe, something in the valvetrain or bottom end has severely broken and you'll destroy the entire engine if you keep running it. I hope this helps. Hell, I feel so bad for you that if you were near North Carolina, I'd check it for you myself...

502Stingray

iTrader: (1)

I didnt have this problem on an LS1, but on my 502, the symptoms are similar, I did exactly what you did, park it, then come back. On mine, a bolt on the rocker arm got loose and the pushrod actually managed to slip off to the side, luckily no damage. If you can, pull the valve covers and double check those, its a simple thing to check for.
One other thing it might be, because it happened on my safari van, was a cam sensor that was messed up and not reading right, so it threw everything outta sync. That would explain why you needed to stay on the throttle to keep it running.
Thats just my suggestion tho, keep us posted to see what the real problem was.

anLS1x2

Okay this is going to sound crazy... but... I'm going to post it anyway. I had my LS1 rebuilt with forged pistons, big cam, 243 heads, etc. etc... after I hydrolocked it. 2 days into driving it again one of my 02 sensors went bad and it sounded like all hell broke loose in the engine. I couldn't keep it idling unless I was feathering the gas. I thought I was about to throw a rod as bad as it sounded. I, in no way, thought it could have been an 02 sensor. I was sure something came loose or broke in the motor. I did some research and posted like you and somebody wrote just about the same thing I am writing now and low and behold that was the problem. I REALLY hope it is yours as well. Good luck and keep us posted.

AintQik

iTrader: (3)

Yeah all hell broke loose in my motor. Dug up the cam, then jammed the lobe up and broke the gear off the camshaft causing the piston to slap a few valves.