ninetres

iTrader: (35)

Need some help brainstorming possibilities. Randomly, the car will be driving fine, I'll floor it, or roll into boost, and the car will instantly shut off once boost starts to roll in. It's not a misfire. The car just turns off. I'm pretty sure the headlights stay on (except when I briefly crank it to restart it). I can click it to neutral while rolling, start it, move it to high gear, step on it and the car takes off like its angry. Totally random. Made several (5ish) hits on the dyno last weekend and it only happened once. What should I be looking for to diagnose??? Stock ECU tuned with HP Tuners by Rick @ Synergy (knows what he is doing).

Ideas:
--Something happen to the PCM?
--All battery power getting cut for some reason?
--VATS issue?
--Loose ground we haven't found? (All 3 on the back of the head are tight)
--Coil or harness issue?
--Alternator issue?
--Something else?

Thanks for your help.

JRENIGAR

iTrader: (37)

pcm=doubtful. batt power getting cut randomly=doubtful. VATS issue=would have a dash light coming on, I think. loose ground=possible. coil issue=probably not and would have missfire codes. harness issue=yes, could be crank sensor wire getting bad connection when engine torques in chassis or anything similar. alternator issue, no, batttery would still run till it got drained and that would be several minutes I would think. Good Luck. Do you have any codes stored?

trans2000am

iTrader: (49)

what are your plugs gapped at? maybe blowing them out?

ninetres

iTrader: (35)

Yea, the crank sensor has been mentioned before. Maybe it got too hot and melted or something as the DP runs right by it. I insulated the **** out of it though The dash looks like it has christmas lights because the car does not have ABS, or 02s, or knock sensors, so the check engine lights are always on. I'm not sure if it thrwe a code but rick had his lap top hooked up to it when it happened once on the dyno when he was tuning it. I imagine he checked to see why it happened. We did a lot of trouble shooting right after that.

Another side note is that the car used to have a two step on it that we determined to be causing a misfire (long story). We totally removed it in its entirety from the car. No more misfire....but it still has this weird issue where the car shuts off.

ninetres

iTrader: (35)

Plugs are gapped at .035. Rick gapped each one himself. Running Shell URT Advanced fuel. Wouldn't blowing the spark out cause a misfire? The car straight turns off....then will work fine until it decides to get fussy again. I think if it was a gap issue it would happen every time.....especially on the 18psi pulls.

Bob@BruteSpeed

iTrader: (16)

Sounds like a wiring problem to me. Bob

JRENIGAR

iTrader: (37)

I had a electric fuel pump on a boat do this and the culprit was a broken hot wire that flopped back and fourth killing the power in right hand turns. Id look for grounds or hot wires to the PCM. I didnt know how extensively modded this car was in my first post. I would also think anything other that the PCM loosing power would store a code.

ren987

iTrader: (4)

When my car was na the bolt that grounds about 3 wires on the back of the head backed out and it would randomly die.

SR-71 SS

iTrader: (2)

my procharger car did this, in my case it was the motor torquing enough for the starter cable grounding out against the frame. Took a while to figure out but for me it was something that simple and stupid.

ddnspider

iTrader: (26)

Had this happen not once, but twice to me. 1st time it was the 2 step being inline with the coils. Removed the 2 step and had them send me another and the issues went away. 2nd time it was a flaky ground wire off the back of the driverside head.

SPRAYED 01

iTrader: (22)

How is your battery held down. Any chance the battery is moving and positive is grounding out?

Louis

iTrader: (7)

PCM is losing power. I had a TT Vette do the same thing 5 years ago, turned out to be a ground wire on the back of the block had come loose. As soon as it needed the good ground under boost, it was like hitting fuel cut.

Ryans99ls1

iTrader: (16)

had this happen as soon as my car came off the dyno. My catch cans would hit the positive battery terminal when the the motor torqued over under full boost. Car would instantly die and everything would reset. It would start right back up and run normal. i ended just covering the battery terminal and moving the cans and its all good.

Even if your grounds are good now, make sure they arent being pulled on once the motor torques over

ninetres

iTrader: (35)

car has solid mounts. still might move a tad... but not much. I'm hitting the shop tonight to dig around. Can't wait to look into it. Thanks for all the ideas so far.

ninetres

iTrader: (35)

only had 2 maf related codes stored. car is sd tuned. amazed there was only 2.

JRENIGAR

iTrader: (37)

Damn, Id honestly let it idle and start slightly pulling and bending/folding wires and connectors under the hood until the car dies. I would also break all the electrical connectors apart to see if there is any black residue inside any of them that would suggest a short or bad connection. I had to do this on my duramax diesel truck to find a shorted wire that rewelded itself back together on the metal bracket that cut it in half. The truck would just randomly die going down the road. BTW is yours an LLY?

ninetres

iTrader: (35)

Headed out to the shop soon. Not sure if its an LLY. How could I tell? Its just a 6.0 iron block.

corpserodeo666

iTrader: (12)

Mine did the same when I relocated the battery to the trunk. For some reason it would pop a relay upfront. I haven't had the issue since I installed a brand new relay. If I remember correctly it was an issue with the ignition relay. Just a thought for something easy to try might work for you.

FasTimeSS

iTrader: (47)

R u logging it?

ninetres

iTrader: (35)

Hit the shop tonight. Pulled and cleaned up every single ground we could find....even if the looked good and tight. Crank sensor wiring looked fine. The sensor BARELY wiggled the slightest bit. Added a washer to the bolt that holds it in and it snugged it up. Added heat wrap to the wires for it just in-case. Grounds on the back of the head looked fine. We removed a lot more of the wires/pigtails we aren't using. We are going to run a bigger charge back wire from the alternator to the battery, and run the 140 amp truck alternator. Currently only was a 4g from battery--alternator. Going to a 0g. (the starter--battery wire is 1g).

We were also using the old racetronix hotwire kit wire (that runs from pump--->alternator) for the 1800hp fuel lab pump that's mounted in the rear. It was pretty small....maybe 10 or 12 gauge. We are ditching that. And running it with 8g directly to the battery kill switch, with a relay.

If the relay was popped I don;t think the ignition would work properly at all.

Not currently. I did just order HP tuners and its arriving tomorrow Can't wait to start geeking it up and watching all of the tutorials, how-to's, and tuning for noob videos!

We will data log it soon. We are even thinking maybe...by chance, the brand new (but small) battery I am using has an intermittent internal short or something. Once we clean up alllll the wiring how we want it on the car....if it still does it, I'll give in and buy a full size yellow top. The car is just so damn heavy I'd hate to do that when there isn't a reason the small, but powerful battery shouldn't work.