Loud noise under acceleration and reduced power ?

2007 2.7 2WD Base auto

Under even moderately hard acceleration there is a Loud 'sucking air' sound. Like a Camaro with the air cleaner left off? Starts and idles as nice as ever. Idles smooth and quiet. Air on or off doesn't matter.

And the power seems to be slowly decreasing. Downshifts for even a slight rise in the road - if I had to guess I would thinking it's only making maybe 60-70HP or so. (I am judging from driving air cooled VW vans <g>)

Any ideas of what it could be? The problem started a few weeks ago and has gotten steadily worse since. Some one local (who didn't see, hear, or drive the truck) offered the idea that maybe the cat. convertor is plugged up? There is no sign of exhaust leakage underneath - and it's not really an 'exhaust noise' type sound. It sounds most like a wide open carburetor sucking in air.

Any suggests as to were to start looking?

 

Under the hood.



Snark aside - have a buddy rev the engine while you are looking/listening to try and trace the sound.

 

Plugged cat !!!

 

Agreed. Had this happen on a Jeep, straight piped it and it had more power than ever.

 

If it's making a loud Hissing sound your cat is plugged , the hissing sound is exh pressure trying to force thru the exh gaskets

If you can loosen bolts to cat converter (engine side - inlet ) , if engine responds /revs easier then that is your problem

 

Typical symptoms of a few different events I've experienced over the years on various marquees.

Clogged fuel filter. Always reveals itself at higher load/speeds first, where more fuel is needed. But not often a noise maker.

Failing cat. When fully failed vehicle may not even start. But failing/partially blocked, like the fuel filter, higher load/speeds is a problem. With noise.

Failing muffler. Yea, sounds stupid, but like the cat, the guts can deteriorate and clog the exhaust flow.

Failing harmonic balancer. Allows timing to move/retard at higher load/RPMs and suck power levels down to nothing. Sometimes this pending failure can be spotted just by looking at the crank pulley at idle, as it would wobble, and worsen with rising RPM.

When you post questions like this, including vehicle mileage, how long you have personally owned it, and some basic maintenance history is usually helpful in our guessing.

Let us know what you find.

 

Sounds like a clogged catalytic converters to me too. Happened to my Syclone and it got so bad I had to floor it just to go 30mph.

 

I still have it. Only 67000 miles on it. It’s a blast to drive.

 

I still have it. Only 67000 miles on it. It’s a blast to drive.

 

I tried that. Under the hood looking / listening I mean. When I did the noise sounded like it was more underneath. So then I listened under there. At which time it seemed like it was more under the hood. <g>

 

My tendency would be to think: all the exhaust parts are the same age, I wouldn't replace one tire - so . . . . time for a whole new exhaust system. But the fact that I have customer's screaming at me, guest rooms in my house still under construction, my son's wedding this coming weekend, and 500 grilled hotdogs to give out on Halloween, and . . . I have to be in Florida (by air <g>) by 11/4 - I have a short-cut question:

Is there any risk of harm to this truck (2007 2.7) or any of it's systems which removing only the cat conv. and replacing it with a piece of pipe? Florida registration on this truck so no vehicle inspection to contend with. If the truck will be OK until then I can just replace the cat along with the rest of the exhaust - say; in the spring.

 

Well my Jeep got so bad it couldn't get past about 30 mph. After cutting the cat out, it ran fine. I honestly don't know what problems it might cause (less backpressure, etc) but I don't think it's too harmful. People do this all the time when their cats are fine, just to get rid of it.

 

Are you really in Clearwater? I'll be in Tarpon/Holiday/NPR in a week or so. <g>

2007 Tacoma Base w/2.7 auto. Purchased about 2012 with about 100K showing. Immediately changed to Mobil 1 and 235/75 LTX's and an aluminum mini spare. Air filter and Maybe a few filter - I can't be positive about the fuel filter though. Presently showing about 165K. Change the oil at 10,000 mile intervals. Some odds and ends repairs over the years. Had an idler noise so I replaced the water pump and all those related pulley's and the belts. Oh; and pressure washed the radiator. New hoses and thermostat and rad. cap. Brakes all around once - fronts maybe twice. And new u-joints one time. I drive it fast but not hard. It has an aluminum work cap and likely 750 lbs. in it all the time. To the best of my knowledge the exhaust is original. Which makes the fact that it looks perfect to me even more amazing. <g>

 

Was this a sudden problem or has the truck been down on power for a while and now you're just realizing things aren't right? I agree with the guy that said to loosen the bolts on the exhaust or separate it just before the cat to see if giving the exhaust an unrestricted path solves your problem. If it does, you've found the problem.

One thing I'd also urge you to look at is your intake tube and make sure all pieces are properly connected. I own a 4.0 V6 Tacoma so I'm not terribly familiar with it's intake layout, but I've experienced a situation where the intake tube became disconnected on my Lexus IS300. The engine was getting more air than it had ever seen but the MAF sensor wasn't because it was located in the part of the intake that was disconnected. Thus, the car didn't think it was getting ANY air and ran like absolute dog shit because the ECU was shitting itself. That would also explain the air noise too since at that point you wouldn't be pulling air through a filter or baffle chamber.

 

MPGs might take a dreadful hit.

 

Thanks but right now I have a lot more gas money than I do garage-time. <g>

 

Funny that you mention that . . . .

For some time there has been an increasing noise, heard more inside the cab, which I was vaguely interpreting as "a buzzy rattle" type sound. Something like what a loose heat shield might cause. None of the heat shields were loose and the noise only happened under high speed acceleration - most especially when, say; passing someone quickly on a two-lane at maybe 60 mph. Or rushing up a mountain highway.

This present sound sort of has some of the same qualities but with the 'no air cleaner small block intake' sucking-air-sound added to it.

Of course now that I am focused on it I think: hmmmm . . . . maybe there Has been slowly decreasing power . . . maybe . . . . <g>

It's pouring rain out this morning but I want to take another peek under as son as it clears up a bit. Because in my memory there is nothing to un-bolt - the exhaust is all welded joints end to end.

No wait: just that quick I can remember seeing a bolt mostly rotted away and thinking when I saw it: Sure looks like it would be a bastard to get That nut off. <g>

Also; funny you mention the intake. It crosses over the top of the engine and so, not too long ago when I was going to replace the spark plugs, I had taken it apart for access. But I've very recently re-checked all the joints and found them secure. It was the "sucking air" sound which made me want to backtrack to the intake.

I think there's a break in the weather - be right back.





[QUOTE="ItalynStylion, post: 16316388, member: 18467"1]Was this a sudden problem or has the truck been down on power for a while and now you're just realizing things aren't right? I agree with the guy that said to loosen the bolts on the exhaust or separate it just before the cat to see if giving the exhaust an unrestricted path solves your problem. If it does, you've found the problem.

One thing I'd also urge you to look at is your intake tube and make sure all pieces are properly connected. I own a 4.0 V6 Tacoma so I'm not terribly familiar with it's intake layout, but I've experienced a situation where the intake tube became disconnected on my Lexus IS300. The engine was getting more air than it had ever seen but the MAF sensor wasn't because it was located in the part of the intake that was disconnected. Thus, the car didn't think it was getting ANY air and ran like absolute dog shit because the ECU was shitting itself. That would also explain the air noise too since at that point you wouldn't be pulling air through a filter or baffle chamber.[/QUOTE]

 

In spraying all the bolts and nuts with Kroil I saw that my down-pipe is bolted to my exhaust manifold with longish bolts pushing on coil springs. The springs are what apply tension to hold the down-pipe flange up against exhaust manifold flange. Thinking mechanically: that seems like a pressure-relief system. Does anyone here know the exact Toyota-Reason? <g>

But if the design intent IS to relieve excess exhaust pressure (say; in the event of a clogged cat. <g>) I am wondering now if that pressure Being relieved is what I heard start small and become gradually louder and eventually reduce the engine's power somehow?

No one had the OEM cat piece in stock. It's an assembly from the exhaust manifold flange thru the cat. thru what I guess is a small resonator (looks like a cat without a heat shield) and then to a flange just ahead of the (really large) muffler. So I got a pipe, a coupling and some clamps the exact size of the after-market cat. they did have in stock.

 

I believe the spring bolts are more for flex so it doesn't break at the flange but I'm not 100% on that.

Why not get under there with someone in the drivers seat. Have them rev the engine up to 4krpm or something and see if you feel or hear any exhaust escaping the flange. Easy, takes 2 whole minutes.

 

Stop at an auto parts store and have them put a code reader on it. If any codes show up, you know where to start. If not. I'd guess it's the exhaust.