1994 Toyota Pickup 3.0L V6 Engine.

I had the engine out to replace the oil pump.
Other new parts installed:
-Timing Belt and idler
-Spark Plugs
-Plug Wires
-Rotor & Cap (but distributor was not moved)

RPMs will fluctuate at idle and will fluctuate if held steady at higher RPMs.
-Re-verified timing marks.
-Checked for Vacuum Leaks
-No check engine light while running

Any ideas on where to look?

 

does it do it only when brakes are applied?

 

No, it does it in neutral with the brakes off.
However, it does have a hard brake pedal.
I have went through the brakes and bleed them.
I drove it around the block and it appears that I am only getting back brakes.
The truck sat for awhile after I pulled the engine out, but it did run without issues before hand except for being well past due for a timing belt (had a loose section in the belt when I pulled the timing cover. When rotating it around the loose spot moved with the belt); and the oil pan was leaking.
I have not replaced (or had the rotors turned) and the pads did not take any of the rust that formed on the rotors. Stopping distance isn't what it should be and at times feels like a non-boosted brake system when on the pedal. That was one reason that I thought that there may have been a vacuum leak, but did not find one. The RPM fluctuations may be affecting the vacuum to the brakes?

 

I could be wrong but I think if the booster diaphragm or the boot around the push rod tears it would cause a difficult to identify vacuum leak. See FSM for air tightness check.

http://personal.utulsa.edu/~nathan-b.../3checksan.pdf