Truck Repair: Low Compression, vacuum gauge, gauge reading

Question
Dodge Truck is '96 model 1500 SLT, with the 5.9L (360) engine, auto trans and 2 wheel drive. Started rough idle and then died at idle, will start again but runs rough.
Compression test rests: 150/150/155/150/160/150/115/155
Obviously the 115 is bad news, so I did the wet test with about a teaspoonful of clean motor oil in the # 7 cylinder and still got the 115 reading.
Seems like a valve job in the trucks future, do you agree? ALso, what would a vac gauge reading relfect so far as for a bad valve?

Thanks for the help!

Answer
Hi Stu,The vacuum gauge would bounce around. It should be about 18, but would probably be about 16 and bouncy.Before pulling the head, if you can remove the gauge from the compression tester, and send some compressed air into each cylinder when the valves for that cylinder are closed. Then listen to the intake, and at the tail pipe, and you can tell which valve is leaking. Check the rocker arms to see if they are adjusted too tightly, and not allowing that valve to close.
I have been known to spray some water into the throttle bore while the engine is running, and bust some carbon loose, which might possible, and that is possibly, knock something loose.
WATER??? You would be AMAZED at how much water can go through there if you are playing with the throttle as you do it.
Now...that isn't a recommendation, but like I said, I have done it with good results, especially on older Dodges that dieseled. The water acts like a sandblaster in the cylinders.
Van