Question

[jimmers]

I was stopped at a red light today and when i went to accelerate my car didnt have any pep to it. As i gave it gas it started shaking, i went through the gears till fourth and it still shook everytime i gave it gas. When i got home i looked around for any leaks or what have you, but nothing. I started it up again, took it for a drive and it was fine. After i got home i noticed a rattling sound coming from what seems to be the catalytic converter. Is it possible that it somehow clogged and caused my car to react that way? Any other ideas of what could of caused this? The catalytic converter is now constantly rattling and i am wondering if i can take it off and put a straight pipe. Are there any sensors in there that i need to worry about? Will the car run worse? Any input would be great!!

 

[Edmond]

That could happen if the convertor is clogged. That would prevent the exhaust gas from fully exiting the vehicle.

Does your model have 1 or 3 convertors? Some models also have the smaller cats just past the exhaust manifolds and the main cat on the pipe underneath the car.

Whether you can take it off depends on your emissions laws. As long as the oxygen sensor is still on there will determine whether a code is thrown or not for the check engine light.

 

[Aurora40]

Yeah, the rattling sounds like either something is loose which you can look for, or there is a piece of substrate that broke off and is rattling around inside. If it's a piece inside, I suppose it's possible it lined up sideways against the rest of the substrate, thus somewhat blocking the flow of exhaust and causing your driveability issue.

 

[srs244]

had the same problem with my Z-28 a few years ago. tried to accelerate and the car just went "flat" through the gears. tried to give it gas and it gave you the same reaction as if the fuel supply was flooding out the engine (like the choke was jammed closed and screwed up the mixture completely). it was definitely the cat. car had 13,000 at the time too, lol.

 

[jimmers]

The laws where i live allow you to take off your cat if its older then a 92. So i took my cat off and put straight pipe but it still shakes when i give it gas. I went to an exhaust shop and he said that it seems that there is debris rattling around in my mufflers that came from the cat. Could that be causing the shake? Any other things i can check before i spend a few hundred to replace my mufflers?
the rattling is definitely coming from under the car....
I have only 1 cat and dont have a check engine light on.
I forgot to mention that it idles alot lower then normal somtimes. And usually when i back up it seems as if its going to stall.

 

[Edmond]

It's possible that it could be the muffler. Is the muffler the original muffler? If so, the original mufflers from our L98's only flow exhaust out of one outlet on each muffler. There really isn't much flow going on back there in the first place and therefore, it wouldn't take much to clog it up.

I have Flowmaster mufflers on my car. I took them off last summer after having them on for two years to repaint them flat black. I noticed that I can hear debris in the muffler. Of course, that's an aftermarket muffler that does flow through both exhaust outlets on each muffler. What I'm saying is that debris in the muffler will happen.

Of course, this could be your perfect excuse to get a new, throatier exhaust system.

 

[jimmers]

i have no idea if they are the original mufflers. I would love to get a new exhaust system but i would just rather find my problem first. When i took the cat off it pretty much crumbled. It all fell out, so i can see that there could be alot of debris in the mufflers. Also When i reved my engine i heard aloud pop come from the back. I dont know if that is a misfore because i have never heard one. Could it be some sort of sensor? The rattling seems to be coming from the middle underneath the car, near the transmission.
Thanks for the quick replies guys!! I have to fix this, it is rather annoying.

 

[Edmond]

Pull each spark plug out and see what they look like. How old are the spark plugs?

With the cat crumbling, it's very possible that all the debri from it has accumulated in the mufflers.

 

[jimmers]

the spark plugs are about a month old so it cant be them. I guess i could always take the mufflers off and just start the car to see how it runs. If it runs fine then i know the problem.

 

[jimmers]

i took it for a test drive tonight and the rattling stopped...so it must just be a loose muffler clamp or somthing along those lines. But i let it idle and it sounds like it has a carburetor. It has a really deep rumble. I know it sounds good but the performance is still really shaky at acceleration. It really shudders when you give it gas. Ive come across some possible solutions that people say it might be, but i would rather have your opinions on here. There are:
1.Fuel pump
2. Transmission fluid
3. O2 Sensor
4. Timing is off ( i checked the timing about a month ago, so i dont think it could be off)
5. Bent driveshaft
6. Loose UV Joints

Does anyone think it could be any of those?
Sorry for posting so much but this is somthing new to me.....

 

[jimmers]

ya thats what i thought so i took it off and its doing the same thing....

 

[jimmers]

im pretty sure it doesnt have upstream converters....i never even knew there was such a thing. As for the front header, is that very common? Can i tell by jsut looking at it?
Thanks for the ideas so far guys!!

 

[G Winter]

If your cat was crumbling inside I would say you have the pieces in your mufflers. Take a sawsall and cut one off in such a way that it can be welded back on. You should be able to hear the pieces when you shake it. Also take it out for a drive and see if there is improvement. If it isn't plugged mufflers it wouldn't cost that much to have one welded back on.
Glenn

 

[1995 RedVette]

Just a thought....Have you had the EGR system checked? If the EGR valve is sticking or not closing all the way under hard acceleration then you will have a lot of exhaust gas being dumped into the intake as the computer starts to add timing and tries to close the EGR valve. This may be causeing your driveability problems. Under light acceleration and crusing the computer allows exhaust gas to recirculate into the intake for economy and other reasons. At the same time the computer compensates for the presence of the combusted gases with the fuel mix with the timing curve. When you slap the throttle, the EGR is supposed to close and computer runs the performance timing and fuel curves.

Just something to think about especially since your car has been in storage. Any decent mechanic with a vac bleeder should be able to tell if the EGR is working properly.

Brett

 

[jimmers]

well i found the problem. On one of my spark plug wires, the contact in the boot was broken. When i pulled it off, the piece fell out. I dont know how it broke but it did. I replaced it and the vette was back! So the car wasnt firing on one of the cylinders causing the rough ride and shake. I just replaced the wires a month ago so this seems weird how it happened. Thanks for all the replies guys!! Good to know that you guys will always try to help out!!