sothpaw2

I had a really strange end to my track weekend at Summit just now. It seemed like the whole thing was marked w/distractions to limit on track time. Basically, when I went faster into T5 after hard braking (Wil H pads now--front only; c5Z rear), I went around the corner and when I went to hit the gas there was no sound.

I looked down & the tach was dead. I don't recall if all the lights died too; I was concerned w/ WTF just happened and get this thing off the track. Instructor suggests a restart--and it did.

So here's what's really, really bizarre--2 laps after I get back on & up to speed, it happened again. Same corner, same place. I restarted by turning the key and didn't leave the surface but lost most of my speed.

After that I went back in again and then back on track again. This time I was careful to take the turn in at a lower speed--my rain speed for this turn. No problems.

Did this all of last session and when my new (my old instructor didn't bother to show up for the session so I got a ride-a-long after everyone else was in session for a while) instructor asked me to push it a little faster--it died again--restarted on surface again.

So...any ideas? Before that last session: I tried tighting the battery terminals (they weren't loose--but did take 1/4 turn), 100% full tank of gas (it only took 7 gal to fill after the 1st incident), topped off brake fluid to the reservoir (near max). Didn't turn off comp. mode though.

Thanks for reading...any ideas appreciated!!

ps...my guess is injectors??? car is near stock w/headers and ECS tuned conservatively for road course.

gkmccready

My WAG is a bad electrical connection (ground?) that takes a bit of load under high-G or a bump in that turn...

davidfarmer

not injectors.

would be nice if you could determine if it was actually shutting down at initial decel (wheels would keep the engine turning, even if it wasn't firing), or actually dying in the corner.

I would think a fuel issue (entire system, pump, pickup etc, not injectors), or electrical as suggested above. You need to find something that would kill it entirely, not just cause it to run rough.

Nothing obvious comes to mind

rbeckham

If the tach was dead at speed, it has to be electrical.

You say you have headers. When I first put headers on my C5, I had a variety of electrical problems as a result of the installer not routing an electrical harness correctly around the header pipes.

The final solution was to install a new harness and route it carefully.

sothpaw2

It was not initial decel for sure. T5 at summit is the only left that is a short lower speed turn after heavy decel. The other lefts are T3 (more of a high speed sweep with very smooth steering and throttle all way through--just scrub off 40% speed in) and T8 (almost a straight, just barely turn and stay on gas).

So...going into T5 you are standing on the brakes. Then throw it a short left. There's no huge bump there...but Summit does have patching now is it's not silk either. It was fine coming into the corner and within a those 10-20 feet it died. It's the high g cornering following high g decel, left only, that gets it. Right turns and everywhere else is just fine.

ps. There are no codes--pulled them after both sessions. Nothing.

I couldn't reproduce this in the paddock by throwing the car left after rapid decel. But it was fun:o

sothpaw2

Could be...I bought the car this way 3 years ago and I know he had some stuff done to protect heat from the headers to the ? plug wires. Thanks for the suggestion--I'll look at that when I change wheels.

rbeckham

We're not talking about plug wires. The wiring harnesses that have to be protected from the header tubes on both sides of the engine include just about everything you can think of. In my case, it started with the ABS and traction control (which of course threw codes) but could have been anything which partially burned through and shorted. For example a ground wire (which could shut down the engine as possibly in your case) or a hot ignition wire, which in my case could quite possibly have burned the car to the ground.

sperkins

My first thought was that maybe that battery was moving causing the sidepost (thank you GM) positive cable to be loose, but you said you checked that (did you check the hold down). I would think it's in the ignition system/wiring/switch. Ever had the ignition switch out? Maybe there's a wire swaying and touching something during that high G turn that is making it short out?

sothpaw2

Yes--I checked the battery terminals (tightened 1/4 turn for good measure--but were not loose to begin with) and the battery mount. That battery had a solid structural connection to the chassis--it was not moving or loose in any way.

My previous experience w/a Firebird would say ignition. I bought the car used, I never had anything done to it but he could have.

So there is a discrete ignition switch? I thought these things had just a PCM and then separate ignitions for each of 8 coil packs? My old F-body had 1 module that distributed the spark (waste spark ignition they called it) so when that went---this happened. But I would not guess it's possible w/the newer set-up.

Z06_BluByU

its sounds like there is a short someplace.. and hard braking is making the wire move just enough to contact a groud point (engine, chassis or whatever) short out and cut the power.. I would check the wires going down to the starter and the wire to the alternator.. also check ALL your grounds.. do a search on here and someone has posted a schmatic with the locations.. from memory there are two just behind the headlight pots on teh frame rail (one on each side), there are two under the door thresholds in the door jamb near the front of the sill (one on each side), there is one UNDER the battery,etc.. there are a few more.. but thats all I can think of right now.. search for that schematic..

oh and also check the wire connections at the ECM/BCM under the passenger side floormat.. battery acid has been know to cook those connections!

put it up on a rack and start looking for loose stuff!

RedLS1GTO

Oh man... I hate electrical gremlins. Especially if they are spuratic like this one they are about impossible to track down. I know that it is a completely different realm, but I had a Camaro that would shut down just like you described on left hand turns. This was on the street, but still similar. Turned out to be exactly what had been mentioned before with a part of the wiring harness run too close to a header and shorted out when the g forces from turning pushed it up against.

JSTAN

Check the ground wire behind your drivers side cylinder head.

If you broke this ground wire, you will lose spark to all 8 cylinders.

96CollectorSport

There are actually two wires that go into one eye, each wire is a master ground for 1 bank of coil packs. It could just be loose and when you really hit the brakes hard it fails to make contact. Not the easiest to get to but a definate possibility. I had it once where only one of the wires wasn't making contact and the car was running on 4 cylinders, made the contact and good as new.

sothpaw2

Thanks for all the suggestions, everyone! I haven't had time to check all these areas and really need to crack open the manuals and find them first. I'll check back w/results.

I know it wasn't hitting the brakes hard that was the cause. It was the high g left turn. There are lots of places on course w/ hard braking zones (and 1 w/more sustained) and right turns. This was the only very hard left. I was ok if I slowed entry speed and didn't corner as hard.


Also--there was no sputter or rough running before or after. It was just suddenly gone--just hit the gas and no response, look down and no tach.

I'll post in c5 tech too about massive ignition failure.