Engine dies, restarts after sitting

[pastorbud]

My son and I have been re-working an '87 Bronco that sat for two years. 302 FI, C6 tranny. We rebuilt brakes, changed fluids, got it running OK. But it has started dying intermittently. No set pattern, but it usually conks out cold after 10-15 minutes of driving. It will re-start after sitting for a few hours. Has new distributor cap, rotor, coil wire, and coil. Has power going into coil, even when it has died and won't start. Has pressure in fuel line. Fuel pump whirs when you switch to "on" position. I'm stumped.

 

[swampthing]

the module on the side of your distributor could be the problem..had that problem with work truck couple weeks ago

 

[firelt90bronco]

How about the egr valave?

 

[pastorbud]

Will start by replacing the ignition module, since that was relatively cheap and easy to get to. Plus, after it dies, I have power at the coil, but no spark, which could be caused by an ECM failure. Will also try changing the fuel filter, since I should have done that anyway (doh!), given it sat for two years. Will let you guys know how it works out.

 

[swampthing]

didnt see that..just saw this post

 

[1982 bronco lifter]

wrong button

 

[pastorbud]

How about the egr valave?

Well, I replaced the module. Problem endures. Idle speed seems uneven when cold. Engine dies when it warms up. May try EGR valve, as you suggest, but guy at parts store said check 02 sensor. Anybody know how to test for these malfunctions before I just start replacing stuff?

Parts store guy says O2 sensor should have between 10 and 20 millivolts coming out of it after the engine warms up. He suspects it is malfunctioning. When the engine is cold, it "ignores" the sensor, but after it warms up, it uses input from the sensor to calculate fuel delivery. Erroneous readings from the sensor could leave the engine "starved" for fuel, or "flooded". (Not literally, it's EFI.)

All sounds credible, but there's nothing in my Haynes manual on it, and it would be a real pain to swap out the O2 sensor and find that did not solve the problem.

 

[pastorbud]

Well there is this from AutoZone:

A sensor that is too loose or a cracked exhaust manifold can result in a lean signal to the computer.

http://www.autozone.com/servlet/UiBroker?F...23d8004f5f7.jsp

And I do have a cracked manifold, so I guess I have to repair that before I dig into this other stuff.

 

[pastorbud]

Well, I replaced the module. Problem endures. Idle speed seems uneven when cold. Engine dies when it warms up. May try EGR valve, as you suggest, but guy at parts store said check 02 sensor. Anybody know how to test for these malfunctions before I just start replacing stuff?
Parts store guy says O2 sensor should have between 10 and 20 millivolts coming out of it after the engine warms up. He suspects it is malfunctioning. When the engine is cold, it "ignores" the sensor, but after it warms up, it uses input from the sensor to calculate fuel delivery. Erroneous readings from the sensor could leave the engine "starved" for fuel, or "flooded". (Not literally, it's EFI.)

All sounds credible, but there's nothing in my Haynes manual on it, and it would be a real pain to swap out the O2 sensor and find that did not solve the problem.

Replaced the check valve. Problem endures, and I have since learned that when it occurs, I have no spark. I posted a new entry, since now I am talking about an ignition problem.

 

[pastorbud]

Had a buddy come over to help me with this, and we happened to remove the cover to the connector in the firewall going into the computer on the driver's side.

Found two broken wires hidden inside the cover. Patched. Fixed. Sheesh.