1993 Sierra Cold Starting Issue
 

Hi all,

Recently, on my GMC (5.0 TBI) I've had a problem starting it when the engine is "cold." In order to start it, I have to press on the gas petal just slightly, to crack the throttle open so it will start. When the engine is warm or hot, I can just turn the key and it will fire right up. The engine, when cold, will crank a few times, "catch" and die before it gets going. Fuel pressure is OK, someone said it could be carbon build-up, because all I do with it is short trips around town. It's worth a look, but I've no idea where it could be building up.

Any ideas? It's not really an issue for me, but the winter is coming up, and I don't want to be "dry-starting" it with the engine revving up every time I go to start it when it's cold. Might as well use no oil at all.

Thanks!

Take off throttle body and clean up, inspect the IAC(idle air control) valve. This will get dirty and prevent it from workin right.

Is the IAC located on the TB? I've worked all around these, but I've never worked on/ identified the IAC on these TBI motors. How do I go about cleaning it? I don't want to damage it by spraying Carb cleaner or anything inside it.

The IAC screws into the side of the TBI on the passenger side. Unscrew it and only clean the tip of it, but clean the orifice it screws into real well. I recommend removing the throttle body completely to clean it right and not wash all that carbon through the motor. It is also a good time to replace the throttle body gasket which is a notorious issue on these trucks. You don't have to but for the extra 10 minutes it takes to remove I think it is well worth the time. Here is what it looks like...

http://t2.gstatic.com/images?q=tbn:A...EtVc_9t51qQihj