Bad idle speed

Yes, that is a very basic resposne. What I would suggest is this. First, check around the engine for damaged or disconnected vacuum hoses. They are about 1/2" in diameter and provide a route for engine vacuum to travel. If there is a leak, it can cause a low and rough idle. Next, as far as the throttle body, I think what the original post ment was to try a cleaner that you mix with the fuel in the tank. If you stop at a parts store and ask for one, I'm sure they will have a few to recommend. The idle air control valve is a different issue. It is mounted on the throttle body (on top of intake). It's purpose is to maintain a steady idle. When they go bad, usually you will experience a looping idle (up and down).
Let me know what you find with the hoses and if the injector helps.

Joe

Have you checked the EGR? Also, have you checked the intake gasket. In 91, there were problems with the intake gaskets.

No, the injectors should be fine. When you replaced the EGR, was the intake clean where it mounts?

Hay, you can ask anything you want. That is why we are here. I will keep my fingers crossed for you. I know they are a pain to get to and I wouldn't want to have to do it twice. However, it isn't uncommon for the intake to carbon up where they mount. Please let me know what you find. If that isn't the problem, we'll figure it out together.

As far as the shops where you are, they are everywhere. I wouldn't trust many of the ones I work with to change my oil.

Good luck and let me know what you find.

Joe

THe idle speed will play a big role in the oil pressure. If the idle gets low enough, the pressure will drop. Just make sure the oil is full. I feel confident what you are seeing is expected because of the low idle.

I wish I could be there too. It would be a no charge. As far as the vacuum hose you replaced, as long as there is no kink in it to restrict vacuum, it is fine.

This is a tough one, but we'll get it. The next thing I need you to check is called the idle air control valve (IAC). It is located on the throttle body. What is does is this. When you let off the gas and close the throttle plate, it allows air to enter the engine preventing it from stalling and maintaining a steady idle. Although a problem with this part usually causes a surge in idle speed. However, it can cause a low or high idle.

I have attached pictures of it so you know what you are looking for. It unbolts from the throttle body. At the end is a pintil that moves in and out. That is what allows different amounts of air to enter the engine. When the idle starts giving you trouble, I want you to disconnect the IAC to see if the idle changes. If it doesn't make a change, there is a good chance it isn't doing anything. I would then like you to remove it and make sure it is clean. At that point, have a helper cycle the key from off to the run position. The pintil at the end sould move. If it doesn't, and it is getting power (you can check the wiring harness with a test light), then chances are it is bad.

Try that and let me know what you find. I'm sorry I keep giving you different things to check, but doing this over the internet takes a lot more time. If I was with you, we could do all of this in a matter of 30 minutes.

Take care and let me know how you make out with this.

Joe
PS: I can't remember if I mentioned this, but the early 4.3L V6 engines did have intake gasket issues. I mention it because that may be our next check. At that point, I will explain how to check it. You can check intake vacuum with a gauge, or use starting fluid or carb cleaner to see if there is a change in RPM's when you spray around the intake. However, I would feel better if you had the spray test done by someone with experience. If the spray hits something hot enough, it can catch fire. Not a pleasant experience.

I forgot the pictures.

Basically, with the engine running, take carb cleaner and spray all around where the intake bolts to the engine. Also, spray it on vacuum hoses, at the base of the TBI. Anywhere there could be a vacuum leak. Please keep a fire extinguisher near by. DO NOT USE WATER TO PUT OUT AN ENGINE FIRE. IT WILL ONLY SPREAD THE FIRE. Make sure the extinguisher is made for oil / grease fires and be careful.

If you hit the leak, one of two things will happen. Either the engine will rev or it will die. You will notice a change in the RPM's.

I will keep my fingers crossed. Let me know what you find.
Joe

Just be careful and I'll look for your reply.

I have to be honest, I'm not sure where to go next other than the computer itself. I'm going to have a different tech review our conversations and see what he thinks. Maybe a fresh mind will help.

Not a problem. I already copied the URL from here and sent it to him. I have one other person that I plan to send it to. Expect a response from them. Also, keep me in the loop.