Hey guys,
I have a '95 Accord LX automatic and whenever the tachymeter goes above 2k while driving I hear a loud vibration/noise. My first thought was that the transmission is going because it also clunks a little when it goes into gear. Then I decided to do some tests to see if it was happening because of the engine speed or because of the tranny trying to switch gears.

First test was as follows, put the car in neutral while parked and rev it past 2k. The results was that there was no sound. Not good news for my tranny.

Second test was to put the car into the first or second gear position and rev the engine while moving. The theory being that the tranny will not switch gears at all and the noise should not happen. The noise DID happen.

So what is causing this noise? It only happens above 2k while moving and doesn't SEEM to be tranny related, but what do I know?!

 

Humm...I'm going out on a limb, which means I'm not 100% sure but offering things to think about or check. I'm sure others might be able to narrow this down more.

Only happens when the drive train is under load? No CEL on, correct? Have you inspected the motor/trans mounts. Also inpsect the CV shafts....does the LX have VTEC?

 

Thanks for the help (on more then one forum )
No CEL, correct. I have suspected the mounts but I am not entirely sure how to inspect them. The funny thing is, the car was making a grinding sound when it was turning left, so I thought, "great! CV joint, no problemo", but when I got there I found the brake guard was rubbing on the brake rotor when the wheel was turned. So I bent the guard away and no more sounds from the wheel. The CV boot was also perfect. This LX does not have VTEC, though I think it was offered.

EDIT: Am I correct in assuming that my tests rule out the tranny? I REALLY don't want that thing to blow.

 

I don't think your tests will rule out a trans problem. But you can continue testing until you find (or rule out) any number of simpler problems.
Check out the engine mounts like Poorman says.

 

Is this a 4 or 6 cylinder?

For the mounts, you can try to push/pull on the valve cover to see if you have movement of the engine. The front mount is easy to see if there is a lot of movement.

Whenever something strange happens at ~2000 rpm, I suggest cleaning the EGR ports. Its something that needs to be done on the accord anyway. There is a writeup in the DIY answers by HondaDude. There other threads covering this subject, so search around.

 

So I pushed on the engine and any movement felt like the suspension, not the mounts.

Anyways, I MAY have identified the problem and, if I'm right, its a stupid one. The previous owner of the car had a new exhaust system installed and it seems as though the mechanic who did it was a bit of a moron. First of all, there is a welded flange thingie near the rear that is broken. More relevant, one of the bolts that secures the exhaust heat shield in the engine compartment is snapped, my theory is that the shield vibrates violently when the engine is at load. There are a few threads still visible that I might be able to screw a very tiny bolt into but, even though this isn't a load bearing bolt, I'm not all that comfortable with that. I'm betting the bolt is VERY seized and Im not too sure how to get it out.

Nonetheless, the EGR is on my list of things to do, right after the FIT valve and the throttle body.

 

You may be able to get vice grips on the head of the bolt. You might have to remove the heatshield then drive the car until the engine gets warm to heat up that bolt. Then try one sharp turn with vice grips on the bolt to see if it will break loose.

Plus removing the heatshield and driving would either confirm or eliminate a rattling heat shield as the source of the noise.

 

So that was my first thought, remove the heat shield, confirm the theory, obvious. Of course things aren't so easy. There are 3 bolts that should hold on the heat shield. The top right bolt is the snapped one (its snapped below the threads, can't get vice-grips on it), the top left one is fine, a little rusty, but fine. the bottom one is strange. It will turn, I can loosen it and tighten it, but I cannot remove it, cant imagine why. As soon as I get it a little looser it seizes up and I can no longer turn it.

 

As far as the mechanic being a moron, lighten up. Some method of fixing things might seem really reasonable at the time. It's not real easy to predict just how corrosion & vibration are going to play out. Some of the hangers & bolt-up configurations from the factory seem like they're NOT the easiest way to do something. But it could be that the "obvious" way will result in strange vibrations or corrosion.

About your strange bolt...
Maybe the threaded bolt sticks out the other side & the exposed threads are badly corroded. As you loosen it, the corroded part backs into the threads & seizes. 50/50 you'll have to break it off & replace it.

 

That is a tough call on what to do. Isn't the O2 sensor bolted on the exhaust manifold, or maybe just below the manifold?

One way to get a out a broken bolt is to use an easy out. That would require drilling into the original bolt. It should get the frozen bolt out. Look for some videos on how to use them.

The easiest thing to do is to pick up an exhaust manifold from a junkyard that doesn't have frozen bolts. The U-Pull-It places are cheaper. You would have to replace the manifold gaskets. This is also the most expensive route.

The last option is to leave it alone for now. Do some of the other maintenance, then come back to this.