Gregamuffin

Hey guys, engine is in, and it will start but i can't keep it running. I have only driven it once and then it died on me and i had it towed home. since then every time i start it it does the same thing: starts, backfires, idles for a few seconds and then cuts out. im leaning towards a VATS problem even though it was supposed to have been eliminated when it was originally flashed. im hoping this video could help you guys help me haha. thanks in advance. almost all sensors are brand new, along with fuel filter, regulator, and lines.
how it's running now:

How it ran the first few times:

ls1nova71

iTrader: (4)

Never heard of VATS coming back, so since it was running before, pretty much rules that out. Have you put a fuel pressure gauge on it, sounds like it isn't getting the correct fuel pressure. Maybe a stopped up filter?

superbean

Back to basics.. lets narrow it down to fuel or ignition. Can you take some ether or carb spray and while cranking can you get it to run if you keep lightly misting it into the intake? If so, that's going to be a fuel pressure problem.. i.e. stopped up filter (did the car sit for a long time - crap in take), what kind of fuel pressure is it making?

If it still persists, then it could be a few things.. like a lousy or missing ground or bad connection to coils, cam sensor, and or pcm. I'm assuming you used a 2000 Camaro harness.. if so was OBDII wired in - Any codes?

Let us know what you find!

Rick Speed

iTrader: (55)

Sounds like its running to rich. I had the same problem. I accidentally put 60pound injectors in with a stock tune. RAn great the first time but after it shut down it wouldn't stay running again until I put the stock ones in.

Gregamuffin

i have a 98 pcm so i have the correct corresponding 98 pcm to go with it. I'm positive about this. I'll have to check my fuel pressure and the carb spray trick to see if either of those work because the car did sit for a long time. it just seems to be so consistent with the way it dies it seemed like it was being shut off by something else.

Gregamuffin

oh and it threw a MAP code, and i replaced that sensor and still nothing

Gregamuffin

it smelled like it was running rich as well, but they are the stock injectors, i checked the parts number on the injectors

superbean

Early LS1 cars have different pinouts to harness for coilpacks. Have you swapped coil pack banks for some reason? May want to try swapping them around. (If it smells like raw gas, may not be sparking)

Gregamuffin

But if it wasn't sparking it wouldn't have ever run. really appreciate the answers and ideas guys, ill be trying things all week while im still on break. maybe my injectors are bad too? leaking?

Old Geezer

iTrader: (3)

The backfire could have taken the MAP sensor out.. Using starter fluid on an engine that backfires, is a good way to lose your eyebrows.
What are they looking at? Headers glowing red, leaks, etc??
Running w/ open headers and getting into closed loop may cause issues w/ the O2 sensor input,,,Could take out the plugs.
Junkyard engine? Injs that have been sitting for a period of time??
First run sounded ok. Was the fuel tank clean? If not, you may have pulled some crap into the injs.
Time to data log it. Post the tune file.

ghettocruiser

iTrader: (17)

Ive told this story on here a few times...but just to put in my little VATS story.

VATS was "turned off" in my PCM before I did my swap. Low and behold on first start up, it wouldnt run. So I ran to radio shack, spent maybe $15, built a bypass box, hooked it up and it ran perfect.

Instead of getting VATs taken back out, I bought a pre-built bypass, installed a plug, and hid the unit in the console. Good security. I just removed the little box and took it with me.

One day, I forgot to plug it in. Fired the car and took off. Took me a while to realize it was still in my pocket. Car did this for months. Then, just as suddenly as it happened the first time, it started to require the box again.

First time it needed the box, I didnt have it. Car was in storage. I was actually able to keep it running for a few seconds with the gas pedal but it sounded horrible.

My tuner said it was all turned off properly when he was in there. So it HAS come back/gone away/come back on its own before. At least in my 99 PCM. The DIY bypass is a cheap and quick way to rule it out if you can solder and there is a radioshack near by.

But it could be something else as others have stated. Just wanted to give that .02 in case you didnt find something else.

J.

ls1nova71

iTrader: (4)

Had this happen to me once, car ran great, then next time I tried to start it, nothing. Pulled the plugs and they were soaked with fuel. Put in a new set and it ran like a charm. From then on, I didn't start it much until everything was done, exhaust, MAF/intake plumbing, ect.

Gregamuffin

Hey guys update after today! Tried the carb cleaner trick and got the engine to stay running! So that means its not a PCM issue and is fuel related. I think the really old stale gas is the problem and it probably sucked some nasty stuff up. Now I'm not sure where to start. I was planning on siphon all the gas out anyway, and I'm fairly confident that my injectors are good. Do I need to replace the regulator? I bought it brand new for this swap. How could I go about cleaning it out? It's the corvette filter/regulator. Just need to narrow this problem down and I should have a reliably running swap!! Thanks again for the tips!

spacemanspif

iTrader: (5)

When you siphon the gas see what it looks like and maybe pass it through a fine screen or some other type of filter medium. If the screen is clean you might be able to get away with just new gas, but if you get a lot of crud you should replace the filter. Either way you go, make sure to check fuel pressure to make sure your pump is keeping up. If you don't replace the filter a fuel pressure check could be an indicator of clogged filter.

Gregamuffin

so siphon the old crap out, put fresh new gas in, see if that works and if not, check my fuel pressure before replacing the filter? the filter would most likely have kept it from getting into the main fuel line right?

ls1nova71

iTrader: (4)

If the filter is clogged then yes, it would stop the fuel. Most likely wouldn't completely stop it, but could be enough to make the fuel pressure low enough to make the engine not run right. This is the down side to the Vette regulator/filter... they're not cheap.

Gregamuffin

Sorry I was unclear, I meant is the clog most likely in the filter? I'd rather not have to replace the supply line all the way to the engine and keep hunting

ls1nova71

iTrader: (4)

Ok I see what you were saying now. The filter will have stopped it from going into the main feed line, but there's practically no way the whole fuel line would get plugged up, even with no filter, the fuel pump wouldn't pump that much crap.
But first, before replacing anything, I would put a pressure gauge on it and see where its at.

Gregamuffin

hey guys, an update...IT'S RUNNING! it was indeed a fuel issue. i had a fuel leak that was almost impossible to find, got that fixed up and it stayed running. which brings me to my next problem, it's back firing now. i have a video listed below where you can hear it backfiring towards the end of the video. during this run it has longtube headers that aren't connected to anything, and only one o2 plugged in. not sure if these or a combination of these would cause a problem but i didn't let it run very long because the backfires were scaring me haha

gagliano7

It is back firing because you don't have an exhaust hooked up yet.