Hello, A strange problem has come up with my 96 4x4 360. My oil light comes on at idle with the truck in gear. In park it goes out. Also the gauge will show about 30psi with the light on! Sometimes at idle, the gauge will drop to 0 for a second, then recover. I am thinking the sending unit is bad. Has anyone ever seen this type of thing? Thanks.

 

Wow, 30 psi definitely sounds low!
On my 360, the needle rests just on the other side of the white line at 40, at idle.
Running it, it goes about another needle's width past that.

The reason your oil light comes on when in gear and goes off in neutral / park is because there is a slight load on your engine when in gear, and this drops the pressure just a wee bit. Then, when you step on the gas, it comes back up.

But I would first check the oil level after the truck's engine has been shut down for a good 5 minutes, on level ground... Make sure that's where it should be.
If the oil is totally black when you do that, I would change the oil and filter as well.
If it has been a long time since you last did this, then it is quite possible that after you run it a few hours / days / weeks, the oil will be totally black again: You'll need to keep changing the oil and filter until it stops doing that.
If you do not do that, I can refer you to some threads here where all the sad news stories relate to what happens.
So, please make sure to always change the oil and filter, every 3,000 miles, religiously.
If you do nothing at all to your truck in ways of maintenance, then at least change the oil and filter from now on.
If the sending unit's not too expensive, get one while you're at the store, replace that too, just for gp.
See what happens, take it from there.

 

Standard troubleshooting of this problem is to put a manual gauge on it. Remove the sending unit (back by the distributer) and thread a hose with a manual pressure gauge into it. Monitor it and if it reads less than 30-35 or so at idle ... consider an oil pump. If it reads higher ... probably the sending unit.

BTW ... having black oil is not a bad thing ... just means its doing one of it's jobs ... cleaning the inside of the engine..

 

Well the 30psi thing was an estimate. My gauge reading sounds very close to what you describe. Oil level is fine and I have kept it changed every 3000 miles. My idle is at about 600 rpm. But can drop to about 200. I think my idle air control is bad, and I have a new one coming. What is the normal idle for this truck? Seems to me I had about 800 before.

 

i just replaced my iac yesterday due to surging/dying idle and it now idles smooth about 750 or so.

 

I think mine sits at about 650. IAC is a good call for a crappy idle like you describe and will cause oil pressure to drop as the RPM's do.