fluttering sound from engine
10-15-2022, 10:28 PM
#1
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Join Date: Oct 2022
Posts: 4
fluttering sound from engine
hi, hoping to use & learn from others' experiences for my problem. I'm getting a fluttering / flapping sound particularly in/around 1500 to 2500 rpm. the sound is more prevalent when the car goes from the stop position to motion and less/barely noticeable if the car is already in motion. thank you in advance. attaching a short video to help you hear the sound.
10-19-2022, 11:37 PM
#3
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Join Date: Mar 2016
Location: Chico, California
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One of my thoughts (and I'm just guessing here) is that the epoxy glue which keeps the halves of the intake manifold together is failing.
When standing infront of the car, looking at the engine, you see the front half of the intake manifold.......if you look thru the gaps in the intake manifold, you can see the back half of the intake manifold. You can see the edge of where both halves are glued together.
Maybe that glue is failing and is allowing air to pass thru a tiny gap between the halves of the intake manifold which is causing the fluttering sound at lower engine speeds.
Maybe, as the engine speed increases, the suction in the intake manifold is strong enough to pull the halves together which results in the gap closing & the fluttering sound going away at higher engine speeds.
I mean typically, when an engine develops an intake air leak, there will be a Check Engine Light with code P0171.......system too lean bank 1.
Maybe if the intake manifold halves are coming apart and is infact leaking air........maybe the leaked air is such a small amount that the A/F ratio sensor is able to adjust Fuel Trims to compensate for the air leak.......
That's a lot of may-be's.
Something I would do is start the engine, run the engine with vehicle in park. Hold the throttle at such a point where the fluttering sound seems strongest. Then with that happening, I'd have someone open up the air filter housing, remove the air filter and see if that changes anything.
If it does, I'd put the filter/box back on the engine and spray starting fluid all around the intake manifold looking for air intake leaks.
When standing infront of the car, looking at the engine, you see the front half of the intake manifold.......if you look thru the gaps in the intake manifold, you can see the back half of the intake manifold. You can see the edge of where both halves are glued together.
Maybe that glue is failing and is allowing air to pass thru a tiny gap between the halves of the intake manifold which is causing the fluttering sound at lower engine speeds.
Maybe, as the engine speed increases, the suction in the intake manifold is strong enough to pull the halves together which results in the gap closing & the fluttering sound going away at higher engine speeds.
I mean typically, when an engine develops an intake air leak, there will be a Check Engine Light with code P0171.......system too lean bank 1.
Maybe if the intake manifold halves are coming apart and is infact leaking air........maybe the leaked air is such a small amount that the A/F ratio sensor is able to adjust Fuel Trims to compensate for the air leak.......
That's a lot of may-be's.
Something I would do is start the engine, run the engine with vehicle in park. Hold the throttle at such a point where the fluttering sound seems strongest. Then with that happening, I'd have someone open up the air filter housing, remove the air filter and see if that changes anything.
If it does, I'd put the filter/box back on the engine and spray starting fluid all around the intake manifold looking for air intake leaks.
10-20-2022, 12:53 AM
#5
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Join Date: Oct 2022
Posts: 4
thank you for a your analysis and pointers. Hard to say with complete certainty but glue seems okay. I have a couple of mechanics look at the sound and visually inspect. their thinking is that either connecting rod or value springs are the culprits. The dealer didn't find anything wrong with belts/pulleys is also pointing to the issues inside the engine. Opening the engine labor is very expensive so I'm trying to seek help from toyota. thanks again.
10-20-2022, 05:56 AM
#6
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Join Date: Mar 2016
Location: Chico, California
Posts: 189
Research this. Copied/pasted from a website........might be on to something.
<<<<<<The VVT-i engine increases low- and medium-speed torque by controlling, in advance, intake valve closing in the low- and medium-speed ranges. With an increase in engine speed, the timing for closing the intake valve is retarded to raise output.>>>>>>>
Your engine is definately making that fluttering sound at low and medium engine speeds.
Engine oil pressure within the VVT solenoid adjusts the valve timing. Higher oil pressure causes the intake valves to stay open (retarded) longer.
Ok, so that's how the valve timing works. Now, think about the intake manifold.
The intake manifold has flaps inside them which operate the "variable intake runner length" feature within the intake manifold. This feature is operated by use of a vacuum actuator. Maybe something's going on with those flaps. Maybe they're stuck open, stuck closed, not moving the way they should. For whatever reason.
Maybe the flaps are stuck closed which is restricting the amount of air from the cam shaft is trying to suck into the engine......if the cam shaft intake valve is open longer, it's sucking more air, but if the intake flaps are closed, maybe the sucked air is more than the flaps can flow.......IDK. Just an idea.
You should be able to move actuator rod on the intake manifold with your finger.........try moving it while the engine is making that fluttering sound and see what happens.
In the automotive repair industry, that sound you call "fluttering" is actually referred to as resonance. It's the sound created due to air vibrations within the intake manifold.
To help eliminate these vibrations, some manufacturers add little air box extensions on the intake manifold tubes to balance out (cancel) the resonance sound. Honda has been doing this for years.
Think about it, all those Honda Civic boys eliminate the intake manifold tubes (with the little air box). Then they install a cold air intake without the little air box and all of a sudden the intake air makes this resonance sound......like the engine is growling. Lol.
Something to look into. But yeah, start the engine. Make it create the fluttering sound and move the actuator rod.......maybe it'll point you in the right direction.
<<<<<<The VVT-i engine increases low- and medium-speed torque by controlling, in advance, intake valve closing in the low- and medium-speed ranges. With an increase in engine speed, the timing for closing the intake valve is retarded to raise output.>>>>>>>
Your engine is definately making that fluttering sound at low and medium engine speeds.
Engine oil pressure within the VVT solenoid adjusts the valve timing. Higher oil pressure causes the intake valves to stay open (retarded) longer.
Ok, so that's how the valve timing works. Now, think about the intake manifold.
The intake manifold has flaps inside them which operate the "variable intake runner length" feature within the intake manifold. This feature is operated by use of a vacuum actuator. Maybe something's going on with those flaps. Maybe they're stuck open, stuck closed, not moving the way they should. For whatever reason.
Maybe the flaps are stuck closed which is restricting the amount of air from the cam shaft is trying to suck into the engine......if the cam shaft intake valve is open longer, it's sucking more air, but if the intake flaps are closed, maybe the sucked air is more than the flaps can flow.......IDK. Just an idea.
You should be able to move actuator rod on the intake manifold with your finger.........try moving it while the engine is making that fluttering sound and see what happens.
In the automotive repair industry, that sound you call "fluttering" is actually referred to as resonance. It's the sound created due to air vibrations within the intake manifold.
To help eliminate these vibrations, some manufacturers add little air box extensions on the intake manifold tubes to balance out (cancel) the resonance sound. Honda has been doing this for years.
Think about it, all those Honda Civic boys eliminate the intake manifold tubes (with the little air box). Then they install a cold air intake without the little air box and all of a sudden the intake air makes this resonance sound......like the engine is growling. Lol.
Something to look into. But yeah, start the engine. Make it create the fluttering sound and move the actuator rod.......maybe it'll point you in the right direction.
10-20-2022, 09:59 AM
#7
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Join Date: Mar 2016
Location: Chico, California
Posts: 189
Here's something I found.......it doesn't have anything to do with Scion specifically.....it's a Ford engine.....but the Ford engine has similar variable valve intake runner length flap design...... Even though the intake manifolds are different, the concept is the same. Listen specifically to the beginning of the video and the vocally stated audio around 9:50
10-21-2022, 11:19 PM
#8
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Thread Starter
Join Date: Oct 2022
Posts: 4
Research this. Copied/pasted from a website........might be on to something.
<<<<<<The VVT-i engine increases low- and medium-speed torque by controlling, in advance, intake valve closing in the low- and medium-speed ranges. With an increase in engine speed, the timing for closing the intake valve is retarded to raise output.>>>>>>>
Your engine is definately making that fluttering sound at low and medium engine speeds.
Engine oil pressure within the VVT solenoid adjusts the valve timing. Higher oil pressure causes the intake valves to stay open (retarded) longer.
Ok, so that's how the valve timing works. Now, think about the intake manifold.
The intake manifold has flaps inside them which operate the "variable intake runner length" feature within the intake manifold. This feature is operated by use of a vacuum actuator. Maybe something's going on with those flaps. Maybe they're stuck open, stuck closed, not moving the way they should. For whatever reason.
Maybe the flaps are stuck closed which is restricting the amount of air from the cam shaft is trying to suck into the engine......if the cam shaft intake valve is open longer, it's sucking more air, but if the intake flaps are closed, maybe the sucked air is more than the flaps can flow.......IDK. Just an idea.
You should be able to move actuator rod on the intake manifold with your finger.........try moving it while the engine is making that fluttering sound and see what happens.
In the automotive repair industry, that sound you call "fluttering" is actually referred to as resonance. It's the sound created due to air vibrations within the intake manifold.
To help eliminate these vibrations, some manufacturers add little air box extensions on the intake manifold tubes to balance out (cancel) the resonance sound. Honda has been doing this for years.
Think about it, all those Honda Civic boys eliminate the intake manifold tubes (with the little air box). Then they install a cold air intake without the little air box and all of a sudden the intake air makes this resonance sound......like the engine is growling. Lol.
Something to look into. But yeah, start the engine. Make it create the fluttering sound and move the actuator rod.......maybe it'll point you in the right direction.
<<<<<<The VVT-i engine increases low- and medium-speed torque by controlling, in advance, intake valve closing in the low- and medium-speed ranges. With an increase in engine speed, the timing for closing the intake valve is retarded to raise output.>>>>>>>
Your engine is definately making that fluttering sound at low and medium engine speeds.
Engine oil pressure within the VVT solenoid adjusts the valve timing. Higher oil pressure causes the intake valves to stay open (retarded) longer.
Ok, so that's how the valve timing works. Now, think about the intake manifold.
The intake manifold has flaps inside them which operate the "variable intake runner length" feature within the intake manifold. This feature is operated by use of a vacuum actuator. Maybe something's going on with those flaps. Maybe they're stuck open, stuck closed, not moving the way they should. For whatever reason.
Maybe the flaps are stuck closed which is restricting the amount of air from the cam shaft is trying to suck into the engine......if the cam shaft intake valve is open longer, it's sucking more air, but if the intake flaps are closed, maybe the sucked air is more than the flaps can flow.......IDK. Just an idea.
You should be able to move actuator rod on the intake manifold with your finger.........try moving it while the engine is making that fluttering sound and see what happens.
In the automotive repair industry, that sound you call "fluttering" is actually referred to as resonance. It's the sound created due to air vibrations within the intake manifold.
To help eliminate these vibrations, some manufacturers add little air box extensions on the intake manifold tubes to balance out (cancel) the resonance sound. Honda has been doing this for years.
Think about it, all those Honda Civic boys eliminate the intake manifold tubes (with the little air box). Then they install a cold air intake without the little air box and all of a sudden the intake air makes this resonance sound......like the engine is growling. Lol.
Something to look into. But yeah, start the engine. Make it create the fluttering sound and move the actuator rod.......maybe it'll point you in the right direction.
that is a very thoughtful and technical response. thank you. I think I got most of it (I'm a novice). to your earlier point, I did inspect for glue and any gaps around manifold - all seem in perfect order. I may sound dumb but I couldn't locate the actuator rod that you wanted me to move. As for other parts such as the housing, pulleys, the dealer did inspect and found to be in good order. They say the problem is coming from inside the engine. I took additional opinions from 2 other mechanics. Both are suspecting a rod knock. I appreciate your time and willingness to help. At this time, I will just submit the car to one of the mechanics.
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