I'm having some issues with my 1999 Navigator and cannot pinpoint the problem. It will not hold regular 1000 rpms and is idling at the lowest possible rpm. You can't even hear it running, just have to step on the gas again and it jumps. Last week, the CEL came on and I got it scanned, popping up p1450 code.

So, I pulled the charcoal canister and emptied it out and cleaned the filters (overall very clean canister). I also dropped the fuel tank and replaced all vapor vent hoses on the tank and canister. Still, nothing has changed. I still need to change out the two hoses at the purge valve, but I'm starting to think it might be something else.

I have not replaced the purge valve or the canister vent solenoid, but was wondering if there's a way to test these functions first before replacing? I did test the power coming out of each wiring harness and both are good.

I'm thinking the culprit is one of these two items, but any help narrowing this down is greatly appreciated.

 

Trouble Code P1450 - Ford Expedition Forum

You can look over the items in this thread.

 

I did check the canister vent solenoid and it is clear. No obstructions at the canister nor any of the vents off of the tank. Is there anything in the actual purge valve that could be causing obstruction or anything to check/clean out in the engine compartment?

 

UPDATE: It seems that it was the IAC valve causing the engine not to idle. Probably should have checked this first, but was stuck on the p1450. Cleaned it up with some carb cleaner and now idling as it should.

However, I'm now getting a humming sound when I'm idling. The noise goes away once I accelerate, but is very noticeable at idle. I assume this means the IAC is going bad? Could I be overlooking something else?