Hi Folks,

I have a 93 F150 4.9 2WD that I'm slowing fixing up. Working to chase down rough idle that feels like a rotating misfire(e.g. smooth->shudder - repeat). I've replaced a bunch of things so far:

TPS
IAC + gasket
MAP
PCV
Intake air charge sensor
Plugs/wires/cap/rotor/ignition-coil
Fuel pressure regulator
O2 Sensor
Coolant Temp Sensor + Thermostat
Also, did a Seafoam treatment in the fuel tank + crankcase

I've noticed some anecdotal improvement to fuel economy and a cold-start has been slight improved, but it still seem to cough and take more cranking than usual to get it started. Once warmed up it starts up fine, but the mis-fire persists. Also another interesting change was after replacing the IAC + TPS, when I cold start the engine, it will hunt up/down the rpm range about 4-5cycles and then settle into it's normal RPM range, never did that before.

I'm going to replace the ICM, and the entire distributor but thought it was time to dig into vac leaks. I have what looks like two major leaks: 1) vapor canister 2) EGR valve. I know it seems obvious but I just wanted to confirm with you fine folks since I've read on the forums that some leaks are by design when the component is not energized. And since the EGR stuff is not cheap, better to measure twice.

Here is a short clip I made showing the leaks:
Many thanks for the help!

 

so based on the fact you replaced things without any reason to, I would say its unclear what the problem is.

First. You HAVE vacuum leaks or you are trying to verify?
Second, any codes... whats the truck doing... what brands did you buy generally speaking...I saw you did PCV, did you do the grommets. How are the hoses for the pcv and booster?

Did you take your vacuum can off the truck and inspect it? It may be rusted on the bottom and thats where its leaking(It should not sound like its leaking)

 

Okay good I saw your video, Im pretty sure the CANP or whatever purge valve is supposed to be closed at engine off, because otherwise that means gas fumes can migrate in your engine. Also your egr should be closed except for when the computer commands it on(with vacuum might I add)

How much presssure does your smoke machine make? if not a lot, nothing to overpower the devices leaking, then Id say yeah... wait I just realized. Can you pull the hose off the canister and plug it, and see if your hose was leaking or the can or the hose leading to the vent line? I am not sure how a pre-96 evap works