Ok, I will try and describe this best I can. Couple days ago I was driving the interstate and all of a sudden the exhaust got noticeably louder with a mild raspy , rapping sound and it started missing briefly. After that everything seemed ok except it still had that sound that I described but only when I would get down on it. This evening it got VERY loud and now does it anytime I give it any gas at all. At idle it is quiet and no unusual noises, and idles fine. Try and take off quick and it will miss with a big loss of power and the sound is a very loud rapping sound like if it had straight pipes with no muffler and you just keep reving the motor. I think the rapping is actually a popping back or miss that is amplified by how loud the exhaust has gotten (its only real LOUD when you give it gas).....I'm assuming it has to be partly something with the exhaust to all of a sudden become so loud !!! No codes. I have checked the exhaust several times now and did find leaking exhaust gaskets. Replaced them with some Felpro, it changed nothing....in fact everytime I have worked on the exhaust everything has actually gotten worse !! Man I am baffled...I have never come across anything like this.
This is a V6 (3.4) With a Ocelot Exhaust from the Fiero store with 1000 miles on it. Ported stock exhaust manifolds. The crossover is the only think I have not actually checked. It is wrapped so I am going to pull it tomorrow and look at it, I have changed the donut at the crossover to the down pipe. Do not have a cat.

I'm I looking in the right direction or could there be something else going on more serious. Will a bad head gasket cause something like this? What would I loook for ? Bad Exhaust valve/s ?
Any suggestions !!!!

Are you using a cat? If so, how old is it?

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" There was a lot of little kids there. I watched them flying, doing jumps, and having races. And I thought that all those little kids are going to grow up someday. And all those little kids are going to do the things we do. But for now, sledding is enough. I think it would be great if sledding were always enough, but it isn't."
--the perks of being a wallflower by stephen chbosky

did you perchance blow out your o2 sensor?
other thoughts: exhaust pipe cracked at muffler, when you race or get on it, the motor rocks and opens the pipe up. this is
likely at any joint tho.
a hung intake valve can also act like that, if you have a modified intake, it will be louder.

Im thinking the cat too,allso try inspecting for a cracked exhaust either down by the cat or by the muffler.The exhaust manifolds allso have been known to crack,use a mirror.Possibly a blown gasket (but that shouldn't cause a loss of power).

quote Originally posted by Dave Gunsul: Are you using a cat? If so, how old is it?

No Cat ...... I have looked at the entire exhaust, just reinstalled the exhaust manifolds today with new gaskets.
I just got in from looking it over again and the only thing I did find was the small rubber hose coming off the ait intake tube to the TB had been laying on the exhaust and it burnt into, I believe it goes to the EGR solenoid.

Is that miss your talking about --popping threw the intake ?

What do your plugs look like?

Like 3800 said . Is it poping threw the intake? If so, start thinking valves and cam lobes, GL

quote Originally posted by 3800superfast: Is that miss your talking about --popping threw the intake ?

Not sure, but it could be. Hard to tell since it is so loud. I will see if I can determine if it is or not today.
Why, what are your thoughts on it ?

quote Originally posted by Jake_Dragon: What do your plugs look like?

I will look at them today, I did notice my new exhaust tips are already black.

[This message has been edited by Zoom88 (edited 09-06-2006).]

Do you still have an EGR tube? It could be cracked... mine did this, and as it warmed, the crack closed up, and the noise went down. But this should cause a code also...

daveg

Was the timing chain replace when the 3.4 was put in? How old is it?
The raspy sound could be from valve timing, bad valve or missing cyl.

Since you say your tips are getting black I would certainly looks at your plug wires also.

Have you run the engine around 1K and pulled the plug wires one at a time to see if there is a cyl. that is not playing the game?
Might watch the rotor and rock the crank back and forth and see how much play is in the chain. If a lot could have jumped a tooth.

But sounds more fuel/Ign. related to me..

Have you check fuel pressure and leak down. Would also do a balance test if you can.

[This message has been edited by Dodgerunner (edited 09-06-2006).]

quote Originally posted by Dodgerunner: Was the timing chain replace when the 3.4 was put in? How old is it? The raspy sound could be from valve timing, bad valve or missing cyl. Since you say your tips are getting black I would certainly looks at your plug wires also. Have you run the engine around 1K and pulled the plug wires one at a time to see if there is a cyl. that is not playing the game? Might watch the rotor and rock the crank back and forth and see how much play is in the chain. If a lot could have jumped a tooth. But sounds more fuel/Ign. related to me.. Have you check fuel pressure and leak down. Would also do a balance test if you can.

Has a cloyes double roller chainn and new sprockets. EGR tube is good.
But here is a pic of the #3 Plug .... got pretty hot.
1 and 5 looked good, haven't pulled 2,4,6 yet.....not looking good !!

[This message has been edited by Zoom88 (edited 09-06-2006).]

Is the end of the electrode melted? Look like that cyl. is running real lean.
Got a plugged injector?

Well, I have unfortunatly found the problem and it is not what I wanted to see.
One of the lifters failed as you can see in the pic and both cam and lifters will have to be replaced.
All the rest of them looked good, I can not push the plunger down at all so it is my opinion that it failed.
Boy did it do a number on the cam lobe !!! Looks like I will be pulling the motor once again....

[This message has been edited by Zoom88 (edited 09-06-2006).]

Ouch
Will a warrantee cover that?

quote Originally posted by Zoom88: Well, I have unfortunatly found the problem and it is not what I wanted to see. One of the lifters failed as you can see in the pic and both cam and lifters will have to be replaced. All the rest of them looked good, I can not push the plunger down at all so it is my opinion that it failed. Boy did it do a number on the cam lobe !!! Looks like I will be pulling the motor once again....

Oh man!
I hate to see that. That just sucks big time!
It frightens me even worse as I have the same cam (I'm guessing you also bought the matching Crane lifters) as you.
It's making me rethink the whole thing. Or making me think about using GM lifters, at the least.

quote Originally posted by Zoom88:

Good night! Is that wear on the side of it too?

quote Originally posted by Jake_Dragon: Ouch Will a warrantee cover that?

Summit told me to send the lifters and Cam back, Crane has a 1 year warranty.

quote Originally posted by Zoom88: I am going back with the same ones....I believe it was just a case of bad luck and I got the one bad lifter !! Only thing I am wondering...what is the likely hood it may have damaged the valve also. Top of the valve train , spring and all looks good and the push rod was not even bent or beat up on the ends. I guess the only safe thing to do is go ahead and pull it for peace of mind. Its still going to put me out of pocket at least a $100 for fluids and gaskets.

I'm thinking the valve is probably okay. Leave both valves closed and pressurize the cylinder. I used my air compressor and the hose off my compression tester. If the cylinder will hold air without hissing into the port (was it an intake or exhaust valve?) I'm thinking everything will be okay.
If someone disagrees, I won't argue. Just MHO.

FWIW, your symptoms sounded very similar to when I broke a rocker stud on an exhaust valve. Whenever I stepped on the gas it would make a WUB-WUB-WUB-WUB sound, that was actually coming from the intake, along with the occasional backfire.

Edit -- You know that there's got to be little bits of metal everywhere inside your engine, now. At least up to the oil filter.

At least remove and flush your oil pump and check the output side of your oil filter. If it didn't clog up and go to bypass, everything past the filter may be okay. Except for what hasn't washed down to the pan, yet.

[This message has been edited by Raydar (edited 09-07-2006).]