Sometimes when I switch from P to D my 1993 f150 5.0 I see the voltage drop and it seems like its going to die. It doesn't do it all the time. I can't figure out if it is electrical or mechanical in nature. It will also do it when I turn my wheel sometimes so that makes me suspect the power steering pump. There is a leak in the power steering system and I have to add more every week. When I turn the wheel I can feel the resistance change several times as I turn it and it is noisy even when the resivour is full, but that does not explain why that would happen when I switch gears. Has anyone had any of these issues with your truck and found the problem. I think the PS pump is binding the serpentine belt and bogging the truck down.

 

Start with the simple things first. Run a self-test diagnostic of the EEC to see if it recorded any error codes. I'm thinking there may be a vacuum leak that's causing the engine to stumble anytime it is presented with a load, like when you put it into gear, or tapping the PS pump when you turn your wheels. So you can try to find a loose hose or plug on a vacuum tree.

 

I did a massive check for vacuum leaks when I first got it cause the lower intake manifold was leaking but I can check again it could be a possibility. As far as running diagnostics I have never attempted it on OBD1 but it sounds like I am going to have to learn.Is there an easier way than using a jumper wire, like a diagnostic code reader designed to be plugged into the connecter. I have a Haynes I guess I'll have to read up on it.

 

Yes, you can get OBD1 code readers, or check with your local auto parts store to see if they can run a free diagnostic for you. The reader may or may not point you to the possible causes.

 

I need to check the IAC valve

 

so its had a tune up, timing has been checked with the spout connector removed. pulling codes will help as this sounds like a possible tps issue.

Now the E4OD will behave this way if the trans filter drops into the pan. might be worth dropping the pan and taking a look. if you havent changed the filter since owning it might be a good time.