DrFlathead

Hey guys. I have a 99 Ws6 (91,000 miles). Just wondering if anyone has any insight into what might be going on. Im not new to engines (built plenty in the past) but this is my first ls1. Out of nowhere my service engine soon light starts flashing and the motor is running REALLY rough. Has a top end sound that seems like its coming from under the intake manifold. Could be a sticking lifter but doesn't necessarily sound like it. Doesn't sound like any loose rocker sound I've heard either. Definitely not a bottom end sound. I'm thinking it could be a misfire, but it has a mechanical "thud" sound every revolution. I do know the stock pushrods can bend if revved too high but i was just cruising when this started, and Im not familiar with what a bent pushrod sounds like in an ls1. I am currently cleaning the spark plugs, making sure all plug wire and coil pack connections are clean and connected but this doesn't sound like a normal misfire,nor does it sound like a loose ticking top end noise, It sounds like a mechanical thud once per revolution from under the intake manifold. I am almost 100% confident its not coming from under either valve cover. Does anyone out there have any experience with these symptoms. Any advice would be MUCH appreciated.

DrFlathead

Ok, just checked it out again. Definitely not the ignition. Its for sure under the intake manifold. "thud" may have not been the best way to describe it. Its more of a VERY pronounced ticking with an ocasional much louder metal slap sound (especially when I rev it a tiny bit off idle) and the engine shakes VERY much especially at low rpms. Does this seem like a bent pushrod to anyone?

jimmyblue

iTrader: (11)

Flashing SES is telling you it's misfiring.

Rockers are known to lose needle bearings, for no
good reason. What you find in your next oil change
might be interesting.

SilverSS07

iTrader: (1)

See what the code is- should tell you which cylinder is misfiring. Swap coil packs to rule that out then go from there.

Daniel Richards

iTrader: (1)

Why don't people scan the code first? if your getting a light see what the computer says.

Sounds a lot like when I had a bad coil pack on my v6, was just driving along and when I pushed the gas a little harder to get up to highway speed the whole car started shaking and running like crap with the SES flashing and it ended up being the coil pack, tested it by swapping out another coil pack from the cars original motor and the misfire went away, so I opted to do all new coil packs the whole way thru and haven't had a misfire code since.

DrFlathead

Thanks for the replies. I just bought an obd2 code reader so Ill see what the error is... Daniel, when you had the misfire did it make any kind of clanking sound. Mine is and its pretty loud.

Daniel Richards

iTrader: (1)

it made some noises but it was a few months ago now so I don't really remember exactly what the sound was like.

Midnight02

iTrader: (8)

The only time I've ever seen the flashing SES light on my car I found I'd broken a ringland and lost a rod and piston. Rebuild followed.

I hope you fare better than I did.

hypno92

Flashing light is due to engine missfire cheak the plus and wires maybe a worn out opti spark may cause this or a timing issue

frisco88

iTrader: (3)

Unfortunately got the flashing engine light and i checked the code and it was engine misfire cylinder #2,so i swapped coilpacks and still the same code,so what can i check now before i remove the valve cover?

Jr.Samples

Did you swap the wire too. Pull the plug. What does it look like?

frisco88

iTrader: (3)

swapped the wire ,haven't had time to do the plug,i'' get it done tomorrow.

KevinR

Really???

Infantrymarine

iTrader: (3)

^^^^

DrFlathead

Didn't realize my LS1 had optispark ignition, LOL

So I ran my scan tool and came back with cylinder 4 misfire.
I had a hunch it was a broken pushrod or a stuck lifter.
I popped off the valve cover and found out my hunch was right.
Broken exhaust pushrod on cylinder 4.

The top third of the pushrod snapped clean in half and wallered out the pushrod hole a little bit, and somehow made its way down in to the lifter valley. Thankfully I was able to get the piece out and after careful inspection looking down the pushrod hole in the head I could see that there was no damage, nor were there fragments down in there. I dropped in a new $6 Melling pushrod, torqued the rocker down to 22lb/ft, buttoned it back up and its running good as new.Changed the oil and no shavings of any kind. Im pretty sure I got REALLY lucky. Could have been a lot worse.

Midnight02

iTrader: (8)

Wow, so there was a major mechanical failure but you still managed to dodge a bullet.

Cole Train

iTrader: (30)

you got extremely lucky

frisco88

iTrader: (3)

so i finally had time to take out my plug and i see nothing wrong with it,so do i do a compression test or just take off my valve cover and look for a bent or broken pushrod or anything else,really don't want to start my car cause i probably won't be as lucky as drflathead and by the way why did you have a hunch it was a pushrod,did you have any noise.thanks

frisco88

iTrader: (3)

drflathead is there a reason why you wouldn't change all your pushrods since you have the valve cover off,because if i remove my valve cover i don't want to do this again what a pain.

KevinR

Changing pushrods is not too difficult. Just FYI, when I had a bent pushrod, it made a noise. I'm not sure that's always the case though. Did you change your plugs already?