I recently purchased a 1994 Silverado it runs great both around town and on the highway. The problem that I am having is if I am stopped and turn the steering wheel to either full left or right the 350 engine will stall. It almost stall (slows down) while I am turning the wheel. It does have power steering. The previous owner replaced the alternator and I did a tune up on it. I replaced the plugs, wires distributor, and rotor. It seems like it is idling fine. It doesn't stall while I am driving it just when I'm stopped and turn the wheel.

I checked the idle speed and I think this may have something to do with it. When the truck is at idle in gear the RPM's are approximately 550 - 600. It is fuel injected so I don't think it's adjustable. There is no check engine light on. Everything elso looks OK. Not sure where to look next.

Check your power steering pump on the pully and if it pulls out from the pump its self.

There is a valve, the Idle Air Control Valve, that may be stuck. This valve controls the amount of air that enters the intake while the throttle plate is closed or nearly closed. Clean the throttle body bore and replace this IAC valve. Good luck and let us know!

. Check/replace the Ignition Control Module (igniter) and coil. Many AutoZone stores can do this for free. Because of the age of your Silverado, and because they are not real expensive, I would replace them. These are key components at the heart of your truck's electrical system.
. Make sure you only installed ACDelco spark plugs in your truck.
. Check the Idle Air Control (IAC) Valve.
. Set idle rpm to specs.

Here's an update. I set the truck to my mechanic he tried the computer, iac valve, replacing and restringing grounds. No change. He recommended I let the Dealer have a shot at it. It went to the dealer. The replace the IAC valve again (connector was broken) then proceeded to spend about $400.00 in labor trying to figure it out. I received a call today say come get your truck we can't figure it out. Any idea's? So far complete tune up IAC valve, ECU, and about 20 hours of labor. Any suggestion would be appreciated.
Thanks!!

I'm embarrassed for that dealer! That wouldn't happen at my shop! You should receive satisfaction if you paid out $400 in diagnostic fees! Did I read that right?? Didn't they offer a diag fee upfront? Did they call you for permission to go ahead after that initial time was spent?

There is a way to test the IAC for functionability and a way to test if the ECM can control the IAC. That whole process may take about an hour. But don't get caught focusing on just the IAC. There are several other things that can cause intermittent stalling; primary ignition, fuel pump, battery terminals pulling loose, etc.

Either way, unless you authorized for them to spend the additional time, you shouldn't be charged for, in my opinion, their incompetence. I wish you could bring it to me!

See if your vehicle is equipped with a Power Steering Pressure Switch. It's an hydraulic pressure switch in the power steering system. When the switch closes, the ECM receives an input signal that cause it to maintain engine speed under high steering loads during parking. It also signals the ECM to increase transaxle hydraulic line pressure during low-speed vehicle maneuvers. Therefore, have this system checked out.

I forgot to mention that the power steering pump was changed by my local mechanic. Yes the dealer did charge me even though they didn't fix it. When I was leaving the service manger said he thought that it was in the distributor. I don't know how much to weight this though seeing what they did. I was going to get a used distributor and hope for the best. Plowing season will soon be here and I need to clean around the property up here in Maine. I did report the incident to GM but nothing much happened. The ignitor has never been change so I guess I could start there.

The pump and the Power Steering Pressure Switch (PSPS) are two different components. The PSPS is located on the power steering rack and gear assembly.

Thanks I'll check it out. I have something new to add. This disease seems to be progressing. Now if the truck is sitting in gear it will stall you don't have to turn the wheel at all. As I watch the tach it will bounce up a little and down and then die. I just figured I'd add that to the mess. Thanks for all your help.

Sounds more and more like the Ignition Control Module is bad.