stng_96

iTrader: (1)

So I am just about done with my 10th anniversary Miata LS1 swap, LS1 from a 2002 Camaro SS, along with the T-56, harness, and ECM. If you want many details then see my build thread linked here:

http://www.v8miata.net/general-motor...10ae-ls1-2392/

For the purposes of my problem here, you really don't have to read much. First and foremost, I sent my ECM to Brandon at LT1swap.com, and he turned off the VATS/EGR/etc. I first got the car started about 2 months ago, and have since stared it several times. Most of the time it has ran fine, sputtering a bit with the TSP 228r, but still ran. Two weeks ago, I was wanting to test that my cooling fans would turn on when the engine got hot enough, so I was running it for longer than normal. After approximately 2 minutes of the car running without trouble, it sputtered out and died. When I tried to restart it, it would fire every time, and die immediately as soon as it came down from that initial hit. Did it probably ten times, with no difference. I could spray some carb cleaner in the throttle body and it would run until it burned that off and die again. Well I gave up for the night, to do a little research. Most things pointed to a fuel pressure problem, so a few days later, I went out to work on it and see what I could make happen. I didn't have my gauge setup at the house, so the only thing I really did that may have an affect was I added another ground along the ground cable going to the rear mounted battery. Well low and behold, it fired and ran fine again........I didn't look any further.

Fast forward to now, tonight I was running it again, ran for about a minute, and is now doing the exact same thing!! I don't think it is a fuel hardware problem, rather something not sending a correct signal and the ECM not sending correct fuel signal. I have read other stories about faulty coolant sensors, MAF's, etc. Anyone have any tips, troubleshooting ideas, etc?

Fierofly

iTrader: (1)

Could it be a battery voltage problem. I let mine sit for awhile and the starter would turn over the engine but would not start. I tried about 5 times then the battery was low so I charged it and it ran first try, I was told the computers won't turn on till the correct voltage, even though there was enough to run the starter. Just a thought.

1964SS

iTrader: (1)

Is the PCM tuned for the TSP cam? If you've got a stock tune with that cam it can do some crazy ****. Is your exhaust complete or open? The O2 sensors will not work correctly if they are too close to the open header.

stng_96

iTrader: (1)

I doubt its a voltage issue, because it always cranks easily and fires, and the battery is new, plus it has ran multiple times without fault.

The computer is not yet tuned for the cam. Changes to the computer include VATS/EGR system removal, rear o2 sensors turned off, tire/gear calibration, and the logic for the 5 wire map I have. Exhaust is Kooks longtubes, (1-3/4 primaries to 3" collectors) to a custom dual system(2.5" stainless) with an X-pipe and the back portion of a borla catback from a C5. I know the car won't run fantastic on the current tune with these things, but it should still, and has for that matter, run at other times. If it was one of those, I don't think it would have run for a minute or two, and then died.

ls1nova71

iTrader: (4)

Get it tuned. My current project would idle fine until I revved it up, then it would die and was hard to restart, all due to the bigger cam. You're kind of pissing in the wind trying to figure out problems until you get a decent tune on it because a lot of them will go away when its tuned properly.

1964SS

iTrader: (1)

Yes it can do exactly that. Actually I've seen them get worse and worse each time the car was started. The PCM is trying to learn and compensate for it's readings. With a stock tune it just can't make the necessary changes to run properly.

Old Geezer

iTrader: (3)

Fuel tank vented?
Data logs?

stng_96

iTrader: (1)

Fuel tank is vented through factory roll over valve, to a one way UPR check valve, then through the miata charcoal canister.

I plan to get the car tuned in the next couple weeks(when I get tires......damn you long lead time tires) but I'm just exploring my options right now. It just seems strange that the car runs great for a bit of time, then does this.....

LS1-450

iTrader: (33)

Sounds like an ETC &/or an IAC problem. From your description, PCM is cutting off fuel as if it has gone into engine protection mode. Won't know for sure without a log. Tuner will be able to confirm what is causing the issue. You may then have to fix it (replace sensor, add sensor or wiring; etc.) before he can final tune.

stng_96

iTrader: (1)

Would it be throwing a code if that was the case? Or they will just see it in the logic?

Also, by ETC to do you mean Electronic Throttle Control meaning the throttle position sensor?

LS1-450

iTrader: (33)

Yah, I typed ETC, but, meant ECT. The PCM defualts to -32*f on a coolant temp failure & reacts by dumping gobs of fuel, of which is the opposite of what yours is doing. It's cutting fuel. For this reason, it may think that the engine is overheating or has no oil pressure for some reason. It seems to be going into engine protection mode. Really, without tuning software, we can only guess. The tuner will be able to watch it happen electronically. The PCM is not seeing something that it needs. May or may not throw a code. We don't know which MILs have been enable or disabled.

stng_96

iTrader: (1)

Hmmm, well I ordered a PLX bluetooth OBDII reader today, I'll see if I can figure anything out with that.

BLKMGK

Are you running it with the gas cap off? After it dies, if you crack the cap does I vent? I read your,build thread - it's impressive - but the venting is a little unclear to me. I've had tanks nearly crush themselves when air couldn't get in and the opposite when they got hot. Starving from a vac in the tank might explain the weirdness...

stng_96

iTrader: (1)

I thought about that as well, that was kind of an afterthought when I first considered the fact that the car may be out of gas......Thanks for the kind words, its been a lot of fun putting the car together, definitely ready to get her on the road.

As far as the venting, the factory miata tank has a rollover valve on the top next to the pump penetration. That is where it vents out from the factory, so I just ran a 3/8" line from there, to a UPR one way check valve that keeps anything from getting back in the tank. I then just ran it straight to the factory miata charcoal canister that I mounted in front of the passenger rear wheel to keep gas fumes down.

Old Geezer

iTrader: (3)

"to a UPR one way check valve that keeps anything from getting back in the tank."
That one way may also be keeping air from "getting back in the tank"....

stng_96

iTrader: (1)

I'll look into it, but i seem to remember that I have the car without the gas gap.....We will see.

LS1-450

iTrader: (33)

Another option would be to buy tuning software (HP Tuner, EFI Live) & a wideband. They each have tuning support forums, as does LS1Tech. We used EFI Live for 8 years before changing to carb.

Having the ability to log & tune allows you to trouble shoot the types of issues you are currently having, as well.

stng_96

iTrader: (1)

Yeah I have looked into HP tuners software, looks very nice, and I can certainly see the value in it. For now I am going to hold off on the entire software package, maybe someday down the road.

stng_96

iTrader: (1)

Threw a fuel pressure gauge on the car just to check, good 60psi or so of fuel pressure at prime, crank, run, and death.

rpturbo

iTrader: (47)

Well thats good, at least now you know it has to be a tune thing turning off your injectors since you have fuel pressure.