7.0sc SuperVette

My car is basically finished-it’s a ’97 M6 LS2 402 w/Vortech T1, 6.5 psi on 11:1 w/ Methanol inj. See my sig.
My one last problem that has come up is it just shuts off.
It’s happened twice now-the first time was 3 days after I got it back and it drove fine, then while idling on a hot day, it shut off and wouldn’t start unless you turned the key off and back on-then it would start normally like nothing happened-drove a few blocks-shut off again, etc.
When it shut off and you put the clutch in and turned the key, nothing would happen, no clicking, no cranking, no sound. Then turn off the key and back on-it starts right up-goes for a few block and shuts off.
Sent it back out to Andy’s-found H2O pump leaking and a fuse for O2 sensor out-fixed but could not duplicate the shutting off problem.
Got it back and drove for a week-several hundred miles-and started to shut off again after 7 days of normal driving-first time on a hot afternoon idling in traffic-eng temp 185-190 only. Same MO, wouldn’t start unless key turned off- then ran for a few hundred feet and shut off, etc.
Flat bedded it to Rydell Chev-they checked it out next AM, found nothing wrong and couldn’t duplicate shutting off!
So I drove it home (2 blks) and there it sits.
It may take days or weeks to happen again and Lord knows where I might be-mtns/desert/fwy!

Someone said that there are recorders that you can hook up to the computer and leave on ‘til it happens?

Anyway—does this sound like anything that’s happened to any one out there?

Also the DIC would say things like reduced engine power, check ABS, check traction control.
I turned the traction control off and it still would shut down.
The diameter ratio of my rear over front tire is 1.032, stock was 1.038, so I don’t think it has anything to do with ABS and the different tire sizes from stock.

Over the year’s I’ve had many problems with this ’97 and it is a marvelous car to drive (see sig), and I think this is the last problem and then it’s perfect-but I don’t know where to start with a problem that takes days or weeks to occur and then won’t be duplicated in a reasonable time for a tech person to observe!

Please help!

Roy

jak112460

Did you make sure you have good oil pressure when this problem happens? I believe that when the oil pressure sender reads low pressure it shuts off the fuel pump. It may shut more than that off. It sounds like it's a heat related problem. Maybe Andy should hang on to the car for a few days and drive it around.

7.0sc SuperVette

Yes the oil pressure was OK at the time, but I will drive it again to dbl check.
The times it started to shut off were in traffic and the car was hot, but the engine was 185-190 degrees and I don't think the oil was especially hot-I haven't had a high oil temp problem.
My worry is that the last time it happend it took 7 days to occur and no professional service person can test drive a car for hundreds of miles and weeks to try and duplicate the problem-that's the horror of the thing!

Thanks,

Roy

leojnknsC5

Traction control is tied into the fuel system. I've had bad tc sensors that have had to be replaced before it was a year old. And a wiring harness in the tc system had to be replaced. I got a "service traction control system" on the dash when this occured.

One more thing: There are two kinds of deceleration, signaled by the TPS and MAP

1. Cut back- shorter pulse widths, closed loop. Light throttle deceleration is an example.

2. Cut off- fuel cut off entirely. Rapid or long deceleration down a long hill. Prevents raw fuel from entering cats. Open loop. But the computer should restart fuel before stalling.

Fuel cut off can occur in the following:
deceleration
power/torque management
overspeed
converter overheat

If your computer goes into open loop operation just before it stalls and is back in closed loop when it starts, it might be the above.

Skunkworks

Traction control module feeds or commands throttle body module. When at full power (no traction control intervention) PWM signal is at 99-100% from traction control to throttle body module. As traction control kicks in it reduces signal which will intern reduce throttle opening at some ratio. Both PCM and throttle body control module look at TPS (throttle position sensor).

Just a suggestion although I’m sure they looked at it, is main grounding lug/strap. I had this problem and would get traction control, active handling, tire monitor system… codes.
Then maybe look at coolant temperature sensor for intermittent fault that would fail high, this may/should shut engine off. I can’t remember max temperature before shutoff but know PCM looks at it.


Mike

7.0sc SuperVette

My '97 has just ABS and TC and I had a wheel bearing replaced a couple years ago which involved a sensor. There has been a lot of changes made by various techs on my car over the last 3 yrs and I do worry about the wiring!
If the idle is a bit rich (with cam/blower) can that couse the converter to heat up grossly at idle and light part throttle?

Roy

Mr. Big

I am going to stick with the old stand by.... My money is on a bad ground wire. I have had what you are describing happen to me. I had a loose wire, sometimes it would be fine, but as soon as it isn't making a good connection, bam off she went. Check the ground behind the head, and the ones on the block. I am sure Andy checked, but just double check

7.0sc SuperVette

I did get a bunch of codes per above-the one that puzzled me the most was the reduced engine power code.
I don't remember any kind of high temp readings and the engine would restart immediately on turning the ignition off, then on.
The type of driving at the time of both shutoff events was idling and light part throttle city driving.

Thanks for your comments-I starting to get ideas of what might be happening.

Roy

leojnknsC5

An engine misfire is more likely to cause a converter to overheat. There is very little fuel involved in an overly rich idle. To protect the converter from overheating the computer actually goes rich to flood the converter with fuel and prevent oxygen from getting to the cat. The fuel doesn't burn until there is sufficient oxygen and the fuel brings the temps down. A misfire is a constantly rich then lean condition. When lean, the extra oxygen burns the extra fuel and raises the temps too high. I think he has it right in looking for a loose ground in the TCS.

7.0sc SuperVette

That's a good thought, as the environment in the engine compartment and the exhaust area heats up there may be movement (expansion/contraction) that temporarily loosens grounds.

Thanks

Roy

SteveDoten

the trans harness has two grounds, one on the dr side of the block and one attached to a stud on the dr side rear frame rail, what codes are you getting? i've had a bad wheel sensor harness(the extensions up front), the car would still operate fine sans tcs/abs

the first pic shows the group of connectors that route next to the batt., the other half includes the ground(between the heat wrap, difficult to see) and the connections to the 2 front wheel sensors

RED99

Even tight, sometimes electrical connections needs to be taken apart and cleaned. Unless they are gold plated.

7.0sc SuperVette

So the harness causes the tc or abs to not funtion but did not shut down the engine?

Roy

7.0sc SuperVette

As I have a '97, maybe the 1st thing to do is clean up and secure all the grounds?
I do see a lot of faulty grounds mentioned on the Forum!

Roy

Red C5

Your problem seems similar to mine when my car was having an overheating problem. Some little bugs like this can be hard to find, mine was easy, the fans were not pulling air because they got wired backwards during the Procharger install. Good luck.

SteveDoten

i'm just providing some pics and info that 'might' help, recently there was a member that had a loose ground on the dr. side head, it's located on the rear of the head

NICK YOSKIN

its pretty high i THINK 28X but if its not that its a very high #

NICK YOSKIN

please provide any codes. one thing that i have learned about these cars is that the tangs in the connectors can get loose and therefor loose connection. you can test and show voltage but when you plug it back in it will not make proper connections. i recently had this problem w/tps. i was getting reduced engine power along with service traction control. codes were 1120 1220 1221 1128

7.0sc SuperVette

I don't work on my car myself so I don't know the codes.
Thanks for your response-I'm going to send the car out for repair in a few days and these responses will help me to make sure everything is checked.

Thanks again
Roy

leojnknsC5

I am curious. Please let us know what you find out.