LS 6.0 starting but doesnt stay running

[Shawn1112]

From 60 to zero was just cycling the key on. Had to wait for someone to get home before I could test it running. Sorry about that. I’m gonna try that tomorrow, i usually use brake cleaner when testing for leaks.

Yes it ran perfect last time I drove it. So I’m like WTF as well. I’m really good at fixing shit, but horrible at diagnosis work.

 

[GLADIATOR]

I would also retorque the intake manifold bolts to eliminate that as a possible leak problem. Rakity rack loud cars sound cool but tend to loosen everything in a car

 

[bikrboy128]

So when you cycle the key it goes from 0 psi to 60 then back to 0?

 

[GTvert90]

So when you cycle the key it goes from 0 psi to 60 then back to 0?

That's how I read it. It should hold steady for 20 - 30 minutes. Sounds like it's bleeding off somewhere.

 

[Shawn1112]

So when you cycle the key it goes from 0 psi to 60 then back to 0?

After about 5-6 seconds its back at zero with just a key cycle, car not running

 

[Shawn1112]

That's how I read it. It should hold steady for 20 - 30 minutes. Sounds like it's bleeding off somewhere.

Kinda what I thought, but the guy that did my build said its normal with my set up.
I'm running the Holley gas tank with Holley 225 pump iirc. Going that route was pretty much plug and play, also all fuel lines are brand new.
Dont smell fuel anywhere and chased all the fuel lines back, they are all dry

 

[bikrboy128]

I'm betting the hose from the pump to the sending unit has a split in it, so its leaking internally in the tank.

I'm not very familiar with the holly fuel pumps but I'd imagine it has some sort of valve to hold fuel pressure.

 

[Shawn1112]

I'm betting the hose from the pump to the sending unit has a split in it, so its leaking internally in the tank.

I'm not very familiar with the holly fuel pumps but I'd imagine it has some sort of valve to hold fuel pressure.

That does make sense

 

[Shawn1112]

Okay so after dicking around with this off and on and getting absolutely nowhere. Towed it to the guy who did the build in St Charles.
He pulled plugs and they looked fine, just a little wet ( I already pulled them and told him that). Pulled the o2 sensor and was completely fucked. Ordered a new one $140 thru it in and car is fine....smfh. Told him why didnt he suggest that to me, and he said it never crossed his mind until the car was there. So talking with Satera he was leaning towards an exhaust leak, but if so we both would have thought the plugs woulda been fouled out as well and they arent. Scott (guy who did my build) was at a loss as well. Only thing he could think of was when Valasquez welded my exhaust to the headers. The o2 sensor sits right there and maybe they fucked it up with all the heat and over time it got worse. I 100% checked for exhaust and vacuum leaks when fucking around with it. I need to get a smoke machine on it to be 100% sure.

So what do some of you guys think? What could have fouled out the o2 that bad to there the car wouldnt stay running?
This o2 comes with the Holley terminator system.

 

[DanJ]

Velasquez in the burbs welded through an O2 bung on a set of headers I took there years back. I wouldn’t put anything past them

 

[LikeABauce302]

Do you have an idle adjustment screw on your throttle body? Try adjusting it to open the throttle blade more at idle. 40% IAC is a lot. At idle, it should be around 5-10%. Once you adjust the idle screw, you have to do a TPS reset.

 

[Jon01]

Got any pics Shawn?
I suppose that the heat could have killed the o2 but itd have to get pretty damn hot.
I think it's more likely the o2 was just defective and didnt die right away.
Glad you got it fixed!

 

[Shawn1112]

Got any pics Shawn?
I suppose that the heat could have killed the o2 but itd have to get pretty damn hot.
I think it's more likely the o2 was just defective and didnt die right away.
Glad you got it fixed!

I'll get a pic from him, I saw it and has to be the worst o2 I ever seen lol
I got this fucker sold and it keeps acting up, now I gotta get it back to my painter for bumper fillers to be repainted.
Ive gotten most of the money from my buddy, I might just tell him take the car and hold what he owes me till the spring time. Then go get paint fixed

 

[Shawn1112]

Do you have an idle adjustment screw on your throttle body? Try adjusting it to open the throttle blade more at idle. 40% IAC is a lot. At idle, it should be around 5-10%. Once you adjust the idle screw, you have to do a TPS reset.

Tried that while I was troubleshooting it and didnt work.

 

[Bob Kazamakis]

I feel like I’ve seen a few talk of the stock o2 that comes with the Holley kits being junk?

 

[LikeABauce302]

I feel like I’ve seen a few talk of the stock o2 that comes with the Holley kits being junk?

It's a proprietary Bosch O2 sensor. The Terminator X can only use the Bosch sensor. The HP and Dominator can use the better NTK sensor.

 

[greasy]

Welding can generate a shit ton of heat and fuck up the O2. Welding gets the metal way hotter than exhaust can so I wouldn’t be surprised by this outcome.