[jmtw]

Hi guys.
My son has a '89 IROC that I rebuilt the engine in (someone else pulled and reinstalled it).
Our problem is after doing all this, when we turn the heater fan on high or the engine fan on, it kills the engine.
it acts like the fans take away the juice that runs the engine.
Any help and/or ideas are appreciated.

[advanced design]

One thought. Do you loose B+ going to the injectors? Do you loose fuel pump pressure? What happens to the ecm data stream when the stall occurs?

Another more likely thought.
Check the location of the grounds for the engine and ecm and verify proper ground functioning with a voltage drop test. Could be a poor ground causing the ecm to shut down.

[jmtw]

Sorry, I have no idea what all that means (except for the ground, of course).
mechanic, I'm not. Just barely the basics.

one odd thing (that may help), is if I disconnect the battery while it's running, then the problem doesn't occur.

remember, simple answers please

[my350camaro84]

whoa whoa whoa. one thing right now NEVER do that. if you disconnect your battery while the engine is running your going to screw up your entire electrical system and could cause a problem like you have right now! so if you've done that before that may have fried something and there's your problem right there. Since it sounds like you don't really know whats going on (no offense) I'd just take it to someone whos good with electrical. when the engine was put back in they may have cut a corner and put wires in the wrong spot.

[jmtw]

admittedly, I do not know alot about late model cars.
But. I do know that the alternator will run the car for short periods of time without hurting anything.
Maybe not on some of the new ones, but this is a '89 model. Not new.
Anyway, if no one can help me here, then I appreciate your time and trouble anyway.

[advanced design]

The basics suggested above are helping to diagnose a problem. The application of the diagnostic steps will help to identify the cause of the engine shutting off.

With the battery disconnected their is no ground path or the ground path for the engine and ecm has been altered. Best guess - check the engine and ecm grounds to be sure they are clean and tight. A ground may well have been left off with the engine installation and I've seen poor grounds cause some strange problems.

Hope that helps.

[jmtw]

Thank you. I'll check that.

[RCastle]

On the left head,at the rear of it is a small ground strap.Check to see if this was installed or not when the installer put it in.It may be loose.On the computer controlled engines there are several grounds.All are important and play a particular role in helping with the flow of power to the components.If the ground is being lost to the engine when you power up the fans this may be your cause.The fan motors are going to go to ground on the inside firewall somewhere.The ground strap mentioned on the left head does ground to the firewall on the outside.If it is there assure that it is tight on both ends.Where it goes onto the firewall it is only a sheet metal screw that holds it there.It may seem to be tight but actually the hole could be larger at the firewall and you will not know it.Allowing for a loss of ground.

[jmtw]

it was a grounding problem, and is now running good.

Thanks guys, I appreciate it.