WTF car dies

I have a 1991 Caprice Wagon w/ a 5.7L out of a 1993 Buick Roadmaster that devoloped an annoying problem about a 2 weeks ago. The car will start when and run for around 10 seconds and just shut off. You can turn the key all of the way off and try to start it again it will do the same thing. If you leave the key on after it dies and i try to start it, it will just keep cranking. If i bring the rpms up the engine will stay running and when i drop the rpms it will run perfectly fine. I have changed the cap, rotor, idle air control valve, fuel filter, fuel pressure regulator, ignition coil, tried and switched the ECM, I have checked to make sure that the injectors pump fuel and they push out fuel until right after the engine dies. So something is killing the engine and it is an abrupt die no sputter or anything. I was just recently told that it could be an oil pressure sensor but if that were the case why would bringing up the rpms make it run. If anybody has any ideas that would be much appriciated. i have talked to the GM Techs at my work and they don't know what it could be. Thanks for any feedback.

Jeremy

The oil pressure sensor has been discussed in detail in previous posts, and contrary to popular belief, will not cut off the fuel pump unless the ECM does not receive a reference pulse from the distributor (since they are in parallel).

A loose ground or power wire to the fuel pump relay?

Have you run a fuel pressure test on it?

I did afuel pressuretest on it before i put the fuel pressure regulator on it. The fuel pressure with the key on would be 13psi and when the key was shut off it wouls drop down to 9psi. I haven't checked for a ground but if it was a bad ground what would explain it running if the rpms were brought up. Thanks for the input to this point keep it coming and i will heck the ground circiut for the relay. Thanks
Jeremy

Is there any chance that it could need a pickup coil in the distributor since HLandin said they were run in parallel. That would explain if there were no pulse to the ecm.

My 89 would start and idle just fine in my driveway at one point. Put it into gear or even just rev the engine and it would die.... Start with the simple things first.... Check your are getting power and ground to the fuel pump.

could it have to do with the cold start settings?
you said that if you blip the throttle and let it settle again, it will be fine...
this sounds like something needs to be mechanically adjusted.

i know that carb cars have a choke setting that is disengaged when you blip the throttle. it cold starts and goes to high idle, you blip it and it goes to normal low idle...

there may be something like this on your car

I changed the oil pressure thing even though some people had told me not to and i didn't fix it. I checked the powers and grounds for the ecm and the grounds on the block and the grounds to the body. i also checked all of the wires into the fuel pump relay and they are all in. When i said bring the rpms up i meant bring the up and hold them for like 15 to 20 seconds. It doesn't always help right away normally it takes 3 to 5 times. My car is a throttle body if that helps anyone. I am thinking about changing the pickup coil even though i think the one that is in there should be good. Well keep the ideas coming i am trying them as they come up. Or if anyone is looking for a nice caprice with an electronic problem that could be fixed with a carb and a regular distributor let me know. Thanks for the input.
Jeremy

Try the electronic module in the distributor. I had an 89 that did the same thing about every 60 or 70,000 miles. Make sure you replace it with a Delco. Definately do not use an Auto Zone.

He said it runs for about 10 seconds then dies, so i think a sensor is bad like a map or something on the tb/intake.

I don't have to bring the rpms up anymore to keep it running. The car is not losing fuel and i have changed the Electronic Spark Control and have unhooked the knock sensor to see if that would fix it. It doesn't it still has the problem. i am so lost i don't know where to go. Keep the ideas coming.
Jeremy

our '96 caprice runs well then just quits and won't start i'm replacing the distributor assembly, and vacuum harness. apparently the vacuum harness has been altered. does anyone know what end goes to what. i know the end with check valves goes to distributor.

I would take the ignition module to advance or auto zone and get it checked. But either use delco,echlin or,standard. If you have a computer safe logic probe. I would check for voltage from switch at the coil. I would monitor the pulse from the pick up coil. Check dist ref pulse from computer. Wiggle connections at coil and distributor. Some the prongs are loose and some break inside from somebody in the past pulling wire to disconnect.

Thank You for your suggestions. I'll test it at Autozone.

I have tested my car and it has spark and fuel until after it dies so that means that all it needs to run is air. i got it tested on a Snap-on scanner this weekend and it picked up a code that not even GM's tech 1's could pick up. it has a code 15 active all the time. That code is High Coolant temp which would close off the idle air control valve and it would not have any air? Does that sound like it could be happening. I am going to change the temp sensors and i would like to know if the sensor in the intake and the sensor in the head both communicate with the pcm or if its only the one i the intake? If anyone knows post, I will post back when i fix it and let everybody know if it runs better. thanks for all the posts thus far.
Jeremy

According to my truck 1991 & 1992 wiring diagram for a 5.7L the two wire sensor with blk and yel wires the computer uses. Check the ohms it probably has an internal ground. Sometimes if they are scaled up you can clean them and reuse.

Mabay linda knows whats wrong with you car you should ask her.

it has a code 15 active all the time. That code is High Coolant temp which would close off the idle air control valve and it would not have any air?

If it does close of the Idle Air Control (IAC) valve, that could definitely explain your problem. The IAC valve help regulate airflow during idling. From what you described, that seems to be the only time your having a problem is during idling. You posted that if you give it some gas (open up the throttle), it doesn't stall. When you open up the throttle, your giving it air and fuel which it needs to run, but if the IAC is staying closed the engine would not breaths.