Ok guys and girls,

First off i love the site, there is a ton of good info up here as well as a bunch of knowledgeable people. I have been reading all the post i can before i posted my problem..

Here goes.

I have a 98 LS1 that has just been rebuilt do to water in the motor.

Bottom end was reassembled by a well known person in my town. He added new main bearings, cam bearings, new rings and i gave him a new ls2 timing chain and a new oil pump. Pushrods were resused as they didnt look bad. I used pistons and lifters out of a 99 Ls1 that had 3000 miles on them when they were pulled so the block could be stroked.

I ordered all new gaskets and head bolts as required. I replaced the coolant temperature sensor(3prong), oil pressure sensor and crankshaft position sensor, all new plugs and wires

The new motor turns over very stong but will not idle very well it will only shudder and backfire, which i figured was a crank sensor beneath the starter, this didnt fix it.

We finally got it to run at about 1500rpms but it was running terrible and backfiring. I looked at the cam gear and crank gear when the motor was assembled and the dots were lined up so i thought. It sounds to me like the motor is out of timing. I searched this site and took alot of recommendations like spraying the intake with wd40 and checking for leaks, nothing was found. I checked the oil pan and it smelled like gas so i drained the oil and replaced it.

My fiance videotaped me trying to start it and if i can get it to load up i will. Disregaurd video is too large

I am desperate for some help in resolving the issue. All cables are plugged in to my knowledge and gas is at 1/4 tank but it is about 2mo old so that could be a contributing factor

Please help the new guy....................

 

Is the maf sensor plugged in and hooked up to the throttle body? Backfiring or spitting through the tb while it's running?

 

yes, i cranked it with it plugged in and without it plugged in an no change. I even ordered a new one and put it in an the same results. Its more like spitting and backfiring through the exhaust but i cant tell...

 

Here is a link to the first video

http://youtu.be/ooIGT-MvlqY

 

This is the second video with the MAF unplugged.. same reults

http://www.youtube.com/watch?v=27Ab6...ature=youtu.be

 

Are your plugs fouled? Just because their new doesn't mean they can't be, double check to see if their wet. Kinda sounds like timing to me

 

Any work done to the heads? Pull plugs and look at those. Can you pull any codes? May steer you in right direction.


Positive your getting fire on all 8 cylinders?

 

yeh thats what im thinking with all the fuel in the oil pan, they might be fouled. I have ran out of time for tonight i will pull the aggrivating plugs out soon and post results. I cant think of anything it can be other than timing. I just dont want to pull the motor back out and take it to the guy to make sure its timed right.

 

also the heads are the stock ones that came off it. Is it possible to put the heads on the wrong side and mess up the running order of the motor. I dont know....

Also the valve guides were replaced with new ones by the motor shop, they were sparkling clean when i got them back so i could have put them on the wrong side of the motor but i may be paranoid..

 

Sounds like timing to me as well. are you sure all of the clips for the injectors and coil packs are plugged into the right spot (none of them are swapped)? Are you getting good fuel pressure? You didn't put a cam in the car and it just needs a tune did you?

 

i plugged all the injectors back into their correct spots all of mine were numbered 1, 2, 3 etc and i put all the clips on. I guess i could have put the coils on backwards maybe it is possible this is the first time ive worked on one of these. It was tuned about 10mos ago and the cam is stock with new bearings..

 

if the dots were lined up on the cam and crank gear, i would be looking at the coil pack and injector connectors.

 

i picked a random plug and it was soaked, so i am assuming all are fouled out i am going to heat them up and try to fix them. have the old set in the garage that have about 5k on them. any thing else i should check.

 

it deff sounds like a timing issue;however if you have a massive vacuum leak like hole in the intake itll do that same thing

 

Wow. It's time to have it towed to a reputable shop.

 

Hey, i am just bouncing ideas out there i have racked my brain on this car

 

Yeah, what he said. We could kick ideas around all day. A fouled plug is not going to cause a backfire like that. If indeed there is fuel in the oil, you have bigger problems my friend.

 

Firstly.... You can't put a LS series head on "backwards". There is no right or left. They are identical to each other.

As far as your "timing" problem... GOOGLE LS1 Crank Relearn Procedure and do it after you verify your wiring to your crank and camshaft position sensors.

 

Well sorry it took so long to get back up here with an update but i have been really busy. Anyways, I decided to pull the valve covers back off because after reading several threads on how to properly put on the rockers i realized this could be my problem. I removed them and the push rods and soaked them in oil for 24hrs, then installed them back and tightened them in sequence according to the gm manual. Car still starts up fine but seems to have a miss in it. I can rev it but it wont go past 3000rpms. All the plug wires are on good and i even changed all coils on one side to just try it, with no difference. I dont know where else to look. Anyone have any ideas. I can post another video if need be....

THanks in advance

 

I had similar sound while I was trying to start mine once before. wasn't engine problem though. My cats were completely clogged somehow.. Hollowed them out and tried again and presto!