Buzzing noise

[hiwaycruzer]

Greetings from northwest Georgia...

I recently started hearing a pulsing, buzzing noise from the passenger foot well under the glove box(close to the firewall). It happens when first starting the truck. The pulses are similar in duration to that of the turn signal. The noise lasts for 5-10 seconds then goes away. After about 10-15 seconds, it starts all over again.
The engine is also much harder to start after sitting a couple of days, usually 2 - 3 attempts with extended crank times. Starts OK w/warm. Also has intermitt high idle. Could these issues be related?

Any help identifying this problem would be greatly appreciated.

1996 Tahoe 5.7 4x4 automatic 180k (fuel pump replaced @90k)

 

[Phone Man]

Maybe a loose vacuum line?

 

[SunlitComet]

It has a pattern so if you are just idling there it is something electric or mechanical. Verify clean grounds and check that all wire and hoses are unbroken and secure. nd check your fuel pressure at the different times of day when you have starting issues. Also do you see any cracks around the started mounting boss on the engine block.

 

[JeremyD]

did you resolve this?
I am having a similar situation. I would say its the same general area maybe even coming from the engine bay through the firewall on the lower passenger side. Sounds like a small portable air compressor kicking on and off or something more like a small vibration. Seems not to be related, to rpm, or motion. Happens at a stop or while moving, but only have heard it with the engine running so far

 

[99'Yukon]

Don't know if it is the same thing you are discribing, but I have been having the same kind of thing happen ever so often. I think i know what my problem is though. I'm thinking that the blend door actuator for the air doors has a malfunction in it. Only hear the sound when messing with the a/c or heat controls for where you want the air to blow. Sounds like a CD syncing in a CD player. Also got in the truck and cranked it this morning, and as soon as the truck started you could hear blend doors swapping around really quick. Damn these fresh air systems on these trucks, i would have much rather just had a cabin filter on these models lol

 

[JeremyD]

Mine is too loud and "heavy" sounding to be a blend door. it also happens whether the climate control system is off or on.

 

[99'Yukon]

Hmm, mine is definitley not as loud as an air compressor and it certainly isn't a vibration. But it also happens whether or not the system is on or off too. Mine sounds oddly like a cd syncronizing if that makes any sense lol. If my problem isn't a blend door, then i'm thinking its the climate control unit itself. Either way a relatively cheap fix if i use this one (AC 15-72547) off of amazon.

 

[JeremyD]

yeah I think I know the sound you are describing, I have heard that too. Definitely a different sound. I noticed my ac light blinks and doesn't turn on if selected, but it is freezing temps here so I am not sure if its supposed to do this or not.


*** Edit*** never mind on the ac thought, I read the manual its supposed to blink if its too cold out

 

[gin_road]

Check under the hood on passenger side. Look for vacuum lines going to heater hoses for heater core. Make sure all these lines are attached and not leaking.

 

[SunlitComet]

yeah I think I know the sound you are describing, I have heard that too. Definitely a different sound. I noticed my ac light blinks and doesn't turn on if selected, but it is freezing temps here so I am not sure if its supposed to do this or not.


*** Edit*** never mind on the ac thought, I read the manual its supposed to blink if its too cold out

where did you read this from?