Vacuum leak

[sean_chot]

I have a 2003 1500 with the 5.7. For the past 2 years the check engine light has been on and thru the key cycle check the only code it has thrown is a p0300 random cylinder misfire code. The issue is a very rough idle in any gear. The rpms will bounce between 500-1500 but if I'm going above 5-10 mph the truck runs fine. It's intermittent occurring about 60% of the time and it seems to happen more when the air temp outside is warmer. I live in Michigan so In 80 degree weather it will happen about 95% of the time. It happens regardless of engine temp. I have checked everything including new o2 sensors, new plugs, new plug wires, new coils, new (used) pcm, clean the throttle body, checked for broken valve springs, switch every other tank from 89 to 93 octane and more. I took off the purge valve and blew thru it and it appears to be sealing. At this point I'm pretty sure it's a vacuum leak somewhere. I did find a crack in the hose going from the charcoal canister to the leak detection pump. I have never had an evap code but my theory is that the leak is before the pump, so when it pressurizes the system, it's not testing the hose with the crack in it. My question is is this crack big enough to cause my truck to misfire and occasionally stall at idle. The crack is about a cm. In length. Thanks for any and all help. Much appreciated.

 

[Redtruck-VA]

Any leak can be an contributing factor. The white plastic clamps don't usually last long and its common for the hose to split over time. But if leaking it should of shown an emission code. Have you cleaned the tb? If it is back firing has it split the intake manifold? Have you replaced the ignition wires? Pcv?
Anytime a 03 has idle/misfire issues I think valve springs. I woul remove all the spark plugs and keeping them in order post pictures of them. With the plugs removed, perform a compression check. This should start pointing at a particular cylinder. A vacuum leak usually raise the idle speed. Are both vacuum hose properly attached?