'88 F150 4.9
The buzzing in the video continues for a couple of minutes after the truck is shut off. Coming from the EGR area. Unplug/replug the EGR vacuum line and it changes pitch (even thoughh the truck is off and the key is out). Eventually it winds down like an electric motor would sound but it is not the fuel pump or the blower motor.

I have recently been troubleshooting the usual 4.9 EGR bucking at road speed and a surging/stalling idle issue on cold mornings.

 

That's kind of exclusive to 4.9 engines of a very few years around that time. Some kind of fan is supposed to cool something after the engine is shut off. Something with the fuel system I believe. Anyway it is supposed to do that.

I think the one on my '88 played out, i don't remember hearing it anymore.

 

Yeah the early EFI models had a blower that ran after shutting the engine down. It was supposed to cool the fuel rail down to prevent vapor lock, although I have never known a fuel injected engine to develop vapor lock regardless.

 

Look for the blower on the pass. side of motor. Look for a flex hose coming from blower to a manifold going under your intake runners. Next time you hear the noise, un plug blower and see if it stops. Mine sounds more like a fan than a buzz. Worth a check.

 

Sorry guys, should have mentioned that fan has been disconnected for years from the looks of it. No, this seems to be coming from the electrical/vacuum do dads bolted to the head right under the EGR valve. Ive been grabbing sensors from the local pull a part (for almost free) to diagnose my idle problem. I'll get a set of these next time.

 

My 93 F250 does that too. I inquired about it once on here and the common opinion seemed to be that it was a normal function...

 

My '93 F250 did it, too, as did my '90 F150, if I recall. I think it's probably just the vacuum reservoir slowly filling with air from one or more of the vacuum-controlled components leaking ever so slightly.

Jason

 

My old 1992 F350 made a "farting" noise after shutting off the engine. I traced it down to the EGR Valve Regulator (EVR). I took it apart and cleaned the filter, that seemed to lessen the noise

 

On further inspection it is definitely the egr vacuum regulator solenoid. I can feel the vibration in my hand. I am a bit concerned as to why it would be trying to operate with the key off. I've pulled the computer and replaced the capacitors but that had no effect on anything.

 

It's not trying to operate. It's the vacuum against the seals bleeding down after the engine is stopped. It's not a problem.

Jason

 

It's not trying to operate with the engine off. It's a controlled vacuum leak therefore it is bleeding off vacuum to atmosphere.

 

Ah. Ok, makes sense.