Mike96z

What do you guys think is causing this?

here's a vid.


Click here to see Video

Mike94ZLT1

You're running open headers... the oxygen sensors are too close to the collector and you're getting messed up readings, causing your A/F ratio to be way off. It's reading lean and dumpin a ton of fuel in there.

BadgeZ28

yep, to rich.

Mike96z

thanks, yea im not driving it like this, i am waiting for my x-pipe and then installing it. i just start it up twice a week and noticed this.

BigBlue95Z

Wayyyy too much gas. Black smoke = rich

Mike96z

Well guys i traded the xpipe for a off road y pipe (hooker that goes with the headers) and I installed it and fired it up, still runs the same, still throws fire out the back and pops etc. Well ive basically taken the o2 situation out of it. Im thinking either bad coil or timing chain. I can also get it flashed back to stock and see how that goes. I dont know the tune history on the engine but the guy did work for a performance shop and im sure it had a tune atleast once. How can I test the coils on the car? or where should I take them? I have a volt/ohm meter. Thanks for any input or ideas. New video coming soon.

Mike96z

as far as testing the wires this is what i found they should be close to.
stock LS1 6 in. - 351 ohms

Mike96z

anyone?

Marc 85Z28

I think everyone has the right idea, but are all attributing it to the wrong component. You could let the O2s hang out in the open and it wouldn't cause that problem

It is likely a fuel issue - too much fuel. I would remove the injector rail as an assembly while keeping the rail connected to the fuel line to inspect for leaking injector(s)

Edit - actually driving the car and starting both cold and a short hot soak would help eliminate a lot of potential causes. You gave us little to no information on an engine swap, with a bunch of unknown parts even to you!

Mike96z

how is it unknown? I know every part on the car. The car has the right fuel setup, the fuel system is correct, the ls1 is a stock ls1 setup with a M6, Hooker LT's, Hooker Y Pipe, F1 Flywheel, Centerforce Clutch. Other than that the rest is stock. Its a 98 SS Motor. I wired it up myself and I know anything you need to know about the vehicle. This has to do either with The timing or coil, im testing the wires and ill pull the fuel rail but im sure thats not an issue.

Mike96z

To me it doesnt seem like too much fuel and there's not really black smoke, what i see is the dust that is being kicked up from the headers. It sounds like it is firing during the wrong time, hence timing, its missing. At idle it sounds fine and doesnt pop but if you listen closely you can kinda hear it cut out. Then once you give it gas, it pops like crazy.

Marc 85Z28

You don't know if the PCM calibration is stock correct?

And why would a timing issue only show on startup, but the second the engine begins to run on its own its OK?

Finally, again, how are we supposed to diagnose an ignition problem over the internet with a short vid of a backfire upon cranking? Now you say that it won't rev up - I see no mention of that in the inital post.

Not trying to be rude or anything, but would you call a doctor on the phone, cough briefly into the phone and ask "What's wrong?"

Mike96z

who said anything about it not revving? it revs fine, but when you rev it pops and backfires as in the vid. I was asking for a diagnosis, just some ideas or what people thought it could be. Im 100% sure the PCM calibration isnt stock but I will have it flashed back to stock soon. The engine is not okay after start up, it pops then once it starts, it sounds good at idle until you give it gas, then it pops and backfires.

Mike96z

sig updated with mods.

Me>you

Did you just install the headers???

If you did, check to see if you cracked any plugs getting them in...Or check all wires and all that stuff