99 Es300 Ufo Like Sound From Under Intake

[greenman1331]

Hello Lexus Owners, - 99 ES300 150,000 miles

I have an odd sound from the underside of the intake manifold near the firewall on the driver side of the vehicle. I have terrible hearing so I had some friends help me do the sound isolation. The sound is rhythmic and deep toned, almost like a pitched down UFO sound in a bad movie. My brother described the sound as "Air moving or escaping". From inside the cabin, it sounds kind of like a knock, but does not have the same metal on metal noise of a knock. Also, the sound diminishes with acceleration which leads me further from lifters/bearings, or other deep engine issues (Does not rule them out though haha). I took a screwdriver and placed it at various places on the engine but that only further convinced me that it is not a deep engine noise. I have no codes to read when hooked up to a code reader.

The sound gets more intense when the car is in gear, stopped and the brake is applied. When the car is moving the noise is either not there or is not perceptible. I don't really have any performance issues except for a slight jerking feeling while maintaining a 35-40 mph speed. At those speeds a slight jerking can be felt as though the car is getting fuel cut outs - pulsing.

I have changed the fuel filter, replaced the intake hoses (I found cracks and gaping holes on one). I changed the oil and ran a magnet through it, the oil looked clean and no metal particulates collected on the magnet. I siphoned out about a half quart of fluid from the transmission to look at the fluid and it is cherry red with no particulates (I had the fluid changed and filter replaced 4,000 miles ago). I replaced the dog bone engine mount, and I'm trying to replace the Trans mount but I can't find the right one yet, old one looks worn but not worn out. I cleaned the intake and sprayed a can of carb cleaner up and down all the hoses and gasket areas of the intake an found no leaks. I changed the spark plugs about 5k miles ago, replaced the pcv valve and replaced the serpentine belt/alternator. I'm thinking it might be an exaust leak, maybe on the EGR valve, but I can't seem to get a definitive answer on whether or not my vehicle even has an EGR valve... Some say yes and some say no because I have the VVT-I system. Looking at a Hayne's manual, I can't find what is in the diagram's they list as an EGR valve.

I'm at a loss as to what it could be at this point, I consider myself to be mechanically inclined and I've rebuilt a few motors, done a few engine swaps and I can fix anything as long as I know what needs to be replaced :) Unfortunately, I'm terrible at diagnosing issues and could use some help.

If anyone has experienced this or has some insight as to what it could be, I would be happy to hear some ideas! Thanks in advance.

[landar]

Instead of a screwdriver, get a short length of some old garden hose and hold one end up to your ear while sweeping the other end around the area under suspicion. You might be able to pinpoint the source that way. Perhaps a vacuum leak of some sort?

[greenman1331]

That may work, thanks for the tip! I've went up and down most of my vacuum lines and sprayed carb cleaner on everything but can't find an intake leak. But it's getting louder and louder closer to the firewall I think. I'll find some hose and report back.