High Pitch Noise (1 Viewer)

[ctross]

Hi team,

Apologies for the long winded post here. About to start pulling my hair out and I'm needing some advice.

I've got a 1994 LC, 1FZ-FE. Just recently replaced the engine from an obd2 long block with a recent rebuild.

After a couple hundred miles, I started getting this high pitched noise coming from the engine(bay) it starts around 1800RPM and the frequency changes with higher RPMS. I would say it sounds like the Jetsons or an old VW bug. The sound happens whether its in gear or park

CEL is on for error 71 (EGR)

When the truck starts, it jumps to around 2k RPM but immediately drops to around 800

Recent work -
Removed all belts, no change
flushed the PS, no change
New knock sensor
New temp sensor
Cleaned Throttlebody
Used VAF installed at time of engine installation
New thermostat and water pump




Trying next:
Timing chain tensioner
Cleaning EGR system

Anything else you'd recommend? About to just take it into a shop..

 

[BILT4ME]

Hi team,

Apologies for the long winded post here. About to start pulling my hair out and I'm needing some advice.

I've got a 1994 LC, 1FZ-FE. Just recently replaced the engine from an obd2 long block with a recent rebuild.

After a couple hundred miles, I started getting this high pitched noise coming from the engine(bay) it starts around 1800RPM and the frequency changes with higher RPMS. I would say it sounds like the Jetsons or an old VW bug. The sound happens whether its in gear or park

CEL is on for error 71 (EGR)

When the truck starts, it jumps to around 2k RPM but immediately drops to around 800

Recent work -
Removed all belts, no change
flushed the PS, no change
New knock sensor
New temp sensor
Cleaned Throttlebody
Used VAF installed at time of engine installation
New thermostat and water pump




Trying next:
Timing chain tensioner
Cleaning EGR system

Anything else you'd recommend? About to just take it into a shop..

Sounds to me like a vacuum leak. It is definitely throttle related in the "surge" I could hear was you pressing then letting off the accelerator.

Check your air filter housing (and the tuna can on the bottom)
Check the air intake hose to make sure it didn't get ripped in the process
Check all the vacuum hoses
Check the PCV valve and hose for leaking
Check to make sure you got all the vacuum hoses for the EGR installed.

The only reason I'm thinking these is because you claim you have the same noise with and without the belts and you're having high idle issues, which tells me that the O2 sensors are seeing something different along with the IAC valve.

Look under the intake manifold for loose vacuum hoses.

 

[ctross]

@BILT4ME, thanks for the suggestions. I'll spend some time this week digging through.

 

[alia176]

I wonder if you have a PS pump gear sprocket whine? On second thought, maybe not as that whine will start as soon as the engine starts then continue to get louder with RPMs.

 

[LandLocked93]

Sounds to me like a vacuum leak. It is definitely throttle related in the "surge" I could hear was you pressing then letting off the accelerator.

Check your air filter housing (and the tuna can on the bottom)
Check the air intake hose to make sure it didn't get ripped in the process
Check all the vacuum hoses
Check the PCV valve and hose for leaking
Check to make sure you got all the vacuum hoses for the EGR installed.

The only reason I'm thinking these is because you claim you have the same noise with and without the belts and you're having high idle issues, which tells me that the O2 sensors are seeing something different along with the IAC valve.

Look under the intake manifold for loose vacuum hoses.

+1 vac leak imo, assuming he was on and off the throttle as @BILT4ME suspects.

 

[Rusty Marlin]

Same vote, vacuum leak.

 

[Bisons]

Late to the party…curious how this one was fixed? Also, can you hear it at idle? Experiencing something similar with my 94. I’ve changed alternator, idler pulley and belts will come next.