I need help on my gasser

[Big Block 88]

We just put out 2000 silvy back to stock for farm duty, factory intake back on factory valve train and can back to stock.

The truck will start then stall and crank again and it won't fire until you give it gas, let off the gas it stalls again. Restart rev it to the moon it smells very rich black smoke coming out the tail and then it will idle.

We just had the fuel pump replaced to 900 bucks thinking it would fix the problem but it did not. The issue with these ls engines is I can't justify throwing parts and money at them when I can go to a junk yard and pick up an entire engine and harness for less than $500.

Yall got any ideas on what's up with this thing?

 

[ryan415]

Check if the fuel pressure regulator is leaking into the vacuum side.

 

[Big Block 88]

Will do thanks for any and all help/ideas

 

[btfarm]

Is this a 6.0? Any codes? Check the throttle plate to bore fit and surface finish. I have a full set of C/K 2000 manuals in my shop if you need me to look but I'm in and out today.

Sent from my SCH-I535

 

[Big Block 88]

This is the truck in my sig. It's the little 4.8 engine. All the parts put back in and in the old girl are what it left the factory with

 

[Big Block 88]

So pulled the top vac line off the regulator there was no fuel present but it has the strong smell of fuel. Truck started and idle fine several times will continue to try it tonight and see if it is fixed.

Looks to be a c clamp that holds it in the rail. I'm really hoping the reg can be changed with out the rail being replaced

 

[ryan415]

Yes, you can replace the regulator itself. It's pretty common for them to leak.

 

[thunder550]

You said back to stock...does it have a stock tune?

 

[Big Block 88]

Yeah we reflagged in the original tune.

 

[thunder550]

If it were mine I'd start by checking the Idle Air Control valve and the O2 sensors. Both you can do with either HPT or EFILive, I'm assuming you used one or the other for the tune.

IAC would be first probably, as the truck will be running in open loop on a cold startup and will not reference the O2 sensors until it warms up some. I melted the IAC wires on my old 2001 at one point, had to 2-foot it home since it wouldn't stay running without my foot on the gas to hold the throttle body open a little bit.

How bad is the black smoke? If it's a little bit and not a lot, I'm thinking that might just be because it's running rich on a cold start.

 

[Big Block 88]

Pretty good cloud on the first rev and the truck is revving ruff missing spittin and sputtering sounds like it's over cammed.

 

[Big Block 88]

Gonna do the reg in the mornin

 

[Veikra]

I've had the same problem on a older truck gmt400. Was my throttle sensor. would make the iac go wide as the ecu was commanded to go with the throttle closed. So the ecu would open up to let air in . Had the rpm stuck at 2000

 

[AKlowriderZ71]

What all was done for returning it to stock?

 

[Big Block 88]

What's in my sig, ls3 intake ls6 rockers lifters cam pushrods and springs. Ls6 throttle body headers no cats 49 series flow master.

Only thing we didn't put back in the truck was the cats as it is primarily an off-road truck for fence duty or herding duty. But the truck didn't have cats when we got it and it was all stock then and ran fine

Ran good but need To be a work truck again

 

[Big Block 88]

I've had the same problem on a older truck gmt400. Was my throttle sensor. would make the iac go wide as the ecu was commanded to go with the throttle closed. So the ecu would open up to let air in . Had the rpm stuck at 2000

Mine won't idle at all. I can rev it till valves float and it does that the (although much earlier than they float with ls6 parts in) if you rev it hard like that then it will idle but idle is below 500 rpm. With the vac line off it is starting fast an idling around 700

Seems to be doing much better with the vac line off it.

 

[Big Block 88]

New fpr in its been running great went out today started it and it stalled. It was cold out so i shrugged it off, restart and slow to start then stall, 3rd time started quickly and idled right up i guess the next issues could be the idle air control in the throttle body?

 

[AKlowriderZ71]

Vacuum leak. What are your MAF g/sec readings at idle?

I'd also get a fuel pressure gauge on it for a cold engine start. See what your fuel pressure is during the cold start and stalling events.

 

[Big Block 88]

I not have my EFI right now buddy is using it. I wonder if I could my cts?

 

[AKlowriderZ71]

Any updates on this??