To start off my car is a 1988 trans am with the 305 tpi and a t5. The car runs fine until it doesn't. While going down the road at varying speeds and throttle settings it will just decide to shutoff. After coasting for like 10 to 15 seconds with it still in gear it will restart itself. I have poked and shaken the harnesses in the engine bay and under the dash to check for loose wires and bad connections. I have tapped on different sensors to see it it might cause something. I pulled down the ecm and tapped around the case to no avail. Nothing I mess with will make it die. I have ohmed out the ignition coil and it is within spec. The pickup coil also checks good. I checked and have 40ish psi fuel pressure with the line disconnected. With it connected at idle it is 35 psi. When car dies the pressure is still where it needs to be. It will start right back up if I am just sitting there idling when it happens. When it happens while driving the only gauge that drops is the rpms. Everything else stays the same which means that it still has power. Honestly I am just not sure of what direction to really go in right now for troubleshooting. Any help would be appreciated.

Adam

 

Man no suggestions? Come on guys. Help a fella out, please.

 

Smells like ignition to me.

Have you wiggled the wires on the coil?

 

That's what I have been thinking. The coil shoots good. I've wiggled the wires going to it and shot the ones from the coil to the distributor. The pickup coil reads in tolerance. The issue is with it being so random I'm afraid that I won't really find out with just using a meter if it's one of the components.

 

If you can wire a light bulb to the + side of the coil and keep it in the car, then when the car dies if the light bulb went out you know you lost voltage to the coil. Other side of the bulb to any convenient ground location.

 

Well I just tried wiring the light and when the car died it did not go out. I had a spare pickup coil for the msd distributor and that didn't change anything. Right now it feels like the coil might be bad even though it checks good. I hate changing parts if I haven't actually called them bad.

 

When you say it starts up again, like on its own or you turn the key and it starts up again ?
Not in my TransAm but another car, I had a problem like this and it ended up being the negative battery cable would wiggle around and cut out but then I'd be able to start it up again but it kept doing it till I realized it wasn't a tight connection.

 

Could be a faulty ignition module too. But I know that leaves you with having to buy a new part to test that theory out, and like you I hate throwing parts at a car like that... Though some auto parts stores may be able to test the module for you.

Only other thing is you're checking the coil when it's room temp. Maybe there's something going on when it gets hot... Have you checked it when it's hot?

From your first post, discussing fuel pressure... I'm reading that to mean that you were monitoring the fuel pressure in real time when the shut down occurred and you did not see any drop or fluctuation in pressure before or during the event?

 

Are you still running the MSD distributor? If so, check the center button in the cap. I was running an MSD cap and had weird problems with the engine running. Discovered that the center button in the cap was barely protruding from the center post. So it would intermittently loose contact with the rotor.

Fred

 

I had a similiar problem on my GTA. Ended up being the connectors on the coil.(clips had broke off) Hit a bump and it would die and then restart while coasting. Took me forever to figure it out.

 

My 91 305 TPI had this issue and it was a bad fuel injector. It would idle all day long but every now and then when I revved it up it would die. It would start right back up after.

I diagnosed the problem by disconnecting 1 injector at a time until it wouldn't die anymore. It was #7 (edit - #2) if I recall. Swapped in a new set and it has been fine since.

Testing fuel pressure -
Getting spark while it dies -
This shows it running with the #2 injector disconnected and dying when I plug it back in -