Take air intake off the TB. Open up the TB and look down into it. You may see pooling of oil. If you do, you are in need of repair.

You can also check the vacuum / pressure in the crank case to show if your plenum is blown. As i understand it, the test it will only show a VERY blown gasket. There is a techincal service bulletin from Dodge on that subject. It will show you how to take the reading. I checked mine using the vacuum guage. Mine showed plenum intact. I went ahead and changed the plenum anyway just in case mine was only partially blown. My plenum gasket was still very much intact when part was changed out!

Good luck.

 

i took off the intake and saw oil residue. what does that mean?

 

^It depends on where it is. If it is near the PCV, it could be dumping oil into the intake, if it is widespread, prolly the plenum.

You'll know if you have a plenum leak. Sh1tty power here we come!

 

Does poor vacuum from a leaking plenum affect the shifting in these trucks... particularly mid to late 90s?