nesluopetan

I need help guys. I have seriously googled this for hours at a time. I have went through hundreds of posts. I have replaced thousands of dollars worth of parts and nothing has helped. I literally have no idea what else to do. I am hoping someone here can attempt to solve this mystery of mine.

first of all, let me say this. The car NEVER did this before I added my procharger. I drove the car hours at a time with zero stalling issues before the procharger.. This only started happening after I added the charger. So naturally I keep asking myself what changed before and after, and everything I have tried hasn't helped.

The problem:

Driving down the highway, 60mph.. light throttle in overdrive. Vintage AC blasting, radio playing the classics.... Life is good. Until the car randomly sputters and dies. I pull over to the side of the road and crank the engine over and nothing. It doesn't even sound like it's creating spark. The engine turns over and over as if the coils were unplugged. I can connect to HP tuners, I can see everything looks good on the logs, it's showing RPM during cranking, it's showing injector pulse, etc.. there are No check engine lights. The car will literally sit there for 30 minutes before I turn the key and it fires right up like it's supposed too.. Then, I can sometimes drive 2 miles or 15 miles and it'll happen again. Sit on the side of the road 30-40 minutes sweating my *** off just to have it fire back up again. Engine temp is good. Doesn't matter if i'm at 1/4 tank or a full tank of gas.

Now the kicker.. THIS ONLY HAPPENS ON HOT DAYS. If I take the car out at 10pm I can drive all night long without a single problem. If I take the car out on a 70/80 degree day I can drive all day long without a problem. If I take it out in a 90+ degree day this will happen, every single time. This is 100% related to heat, but I don't know how to narrow it down from there because the engine temp stays at 200/210 degrees regardless how warm it is outside.


Now, What I've done to narrow down the problem:

1. installed a fuel pressure gauge. fuel pressure stays steady, even up to the point where the car dies. When I turn the key I can hear the pump prime.

2. I have installed an aeromotive EFI tank made for my chevelle with an in tank 340 pump. I thought my car was vapor locking due to my old in line pump being higher than my sumped tank. So I purchased this new setup $700+ and nothing changed.

3. I completely removed my corvette regulator/return setup and installed a -8 feed, in line filter, aeromotive fuel pressure regulator and new rails. completely new fuel system and completely new fuel pump wiring / relay. every single piece of my fuel system have been replaced.

4. I checked all the grounds on the PCM, engine, frame, etc. Grounds are all good.

5. The fuel line is not located next to headers/exhaust.



This is where I'm at. My car is a double edged sword because it's so much fun to drive.. The car makes 600+ wheel, it's a total blast but I still have this one gremlin. The wife refuses to go in the car until I can prove it's fixed because the car died on us again a couple weeks ago after the new fuel system was installed. having a broken down car along with a pissed off wife with a 4, 2 and 1 year old wasn't fun on a 100+ degree day.

I am seriously at a loss. I would swear it's fuel related but I have replaced EVERYTHING to do with the fuel system. My fuel pressure is steady. It's almost as if the ECM is stopping the spark due to a sensor failing when it gets too hot. I've seen on other random threads people were saying it could be my crankshaft position sensor..

one guy said: "Might be your crankshaft position sensor fixing to **** on you. mine when it would get hot would shut the car down and take about an hour to crank back"

Another guy said: "IF THE INTERRUPTION IN THE SIGNAL FROM THE CRANKSHAFT POSITION SENSOR IS SO BRIEF THAT THE ELECTRONIC CONTROL MODULE (ECM) LOGIC DOES NOT HAVE TIME TO DIAGNOSE THE CONDITION, THE ENGINE MAY STOP RUNNING WITHOUT WARNING WHILE THE VEHICLE IS DRIVEN AT A LOW SPEED INCREASING THE RISK OF A CRASH."

I just don't know. I don't think it's the crank sensor because I can see spark when I try to start the engine in HP tuners. If the sensor were bad, I wouldn't be showing RPM. The only things that were changed when my procharger was installed were:

1. converted from 6.0 truck accessories to all corvette based accessories.. new corvette alternator, water pump, power steering, pulleys, etc

2. I moved my ECM from the driver side inner fender to the passenger side engine firewall. I used the same painless harness which had plenty of slack.


Can an ECM get too hot and go into some type of a fail safe until it cools down? Obviously it gets hot when the fans are blowing all that air against the firewall, and my ECM is mounted to the firewall. I have always been under the impression the ECM's can withstand engine bay temps.

Does anyone have any ideas? I'm seriously ready to sell my car because of it. I don't trust driving it and the whole reason I have this car is because of how fun it is to drive. If anyone can help me figure this out I'll be very grateful. I'm stumped. What will cause a car to do what mine is doing only when driving on hot days? what sensor could cause this? Where do you suggest I start?

Exidous

iTrader: (11)

You need to see if there is spark at the plug during this 30 min dead time. HPTuners only tells you that the processor is trying to send a spark. Not that one is actually occurring. Same holds true for the injectors. Is there any gas small while cranking?

Just keep a spare spark plug with you and pull a wire off.

Just about any of the sensors can cause this. It's important to log as many sensors as you can in groups. Do JUST temp sensors then just angle sensors and so on to get the highest resolution you can.

PCM's can overheat but the reason why the use "old" technology compared to say a cell phone is how robust they are. They can take more environmental abuse than most other electronics.

nesluopetan

I am 90% sure it is not sparking or firing the injectors during this dead time. I can still access the ECM through HP tuners so I know it at least has power ran to it and it's responding, but other than that I don't think it's throwing any fuel or spark in the motor. I do not smell fuel and if the car were sparking it would at least sputter and act like it wants to light. Immediately after the car dies I can try cranking and nothing happens.. Just turns over and over without a single attempt or sputter. I can verify for sure though next time it happens by taking a spark plug with me like you mentioned. It's so hot and miserable when this happens and it always seems to happen at the one area where there is no shade or trees to pull under. Murphy's law I guess.

As far as the ECM overheating. The ECM is being put through way more heat where it is now, compared to where it was. Before it was over on the driver fender whereas now it's mounted on the firewall and facing direct heat. I can't put it back on the fender due to the supercharger being there. There is really no where else to put it in the engine bay. If I want to move it I'd need to unpin the harness and find somewhere inside the car to mount it, which won't be easy. They are big bulky things that's for sure.

If we go under the assumption there is no spark/fuel where do you suggest I look next? Thank you for the reply.

Exidous

iTrader: (11)

It's important to find out if it's not getting spark, fuel or both. With no fuel smell I'd bet the injectors are not firing. Verify spark just to be sure. If the injectors are not firing it's either a bad 12v source(pink wires) or the injector drivers and failing to fire. I doubt it would be the ground between the injectors and PCM as those are 8 independent circuits.

With the car failing to start and ign switched on check that there is 12v on the pink wire. You can check at any of the 8 injectors. If you have 12v there it's the PCM not firing the injectors.

BTW, all pink wires in the LS1 harness are 12 volt switched coming directly from the ignition unless you are running a relay. With a relay the ignition actuates the relay and power through the relay is sourced directly from the battery. Orange wires are 12v always on.

jimmyblue

iTrader: (11)

Can you try force-cooling the PCM when this is
happening? Like, bring with you a 12V muffin fan
with some clamp-on cabling so you can raise the
hood, cool the PCM and see if this fixes things?
You could also pick up a can of freeze spray at
an electronics store, could be quicker but only a
limited shot.

What do you see for IAT readings and IAT spark
retard (if there is no spark at all, this does not
matter, but too much underhood heat could just
pull too much timing to live)?

RockinWs6

Well I'll tell where I would start, get it hot till it stops and check the injectors AT the injectors with a light and check for spark with a spare plug.......then move on from there. You need a starting point of some kind.

Darth_V8r

iTrader: (4)

I was going to ask the same question - would it be worth trying to insert a 4.7k ohm resistor into the IAT connector to force something stupid like 60 degree temps and see if the car still cuts out?

nesluopetan

I am going to take a test light with me the next time I go out, in case this happens. I will then check the pink wires at the injectors. Excuse my ignorance here, but if there is no power at the pink wires anywhere in the harness, wouldn't that mean the ECM wont have power as well? When this happens I can connect via HP tuners, I can make changes to the tune, I can upload changes, I can watch the graphs live.. The ECM clearly has power, even if the injectors or coils don't. I can start checking wires 1 by 1 through the painless harness when this happens and verify which wires are getting power. I hope the weather stays warm so I can check. It's supposed to start cooling down here and the second the season changes I'll be forced to wait until next year before I can verify anything. Thanks again for the replies. You have all been very helpful.

Exidous

iTrader: (11)

Generally yes, the PCM would not work but a break somewhere is always possible however unlikely. Better to know for sure.

joecar

In your driveway aim your wife's hair drier at the PCM and see if you can induce the problem.

Exidous

iTrader: (11)

Or a heat gun used sparingly and evenly but that's a good idea.