Alright I need some help from y'all. I have my 94 3.4 L 5spd and I just replaced the coils the plugs and the wires and had it tuned. because it has bad acceleration now and the cat converter seems bad. When I rev the motor in neutral it Revs up and then makes a clankin type of sound from underneth the car, and was wonderin if y'all think it is the cat converter or could it be something else. I could really use some help thanks.

 

When my cat went it started to rattle at idle, so it could be that.

 

Sounds like the cat starting to melt. My car did that. Usually the more imortant question, unless you hit something in the road like i did, is what is part of the metalic block rattling around in the houseing? Something had to melt or compromise it. A direct fit cat runs about 200 bucks at Nappa, i think just over 100 bucks for the pep boys junk. Unless you want my hollowed out cat.

 

Is your SES light on? How does the exaust smell? I would prolly have to say that it's your cat. What are some other symptoms that your running in to? Ex. Stalling, Missing, bad fuel economy, stumble under part, OR full throttle acceleration. Get back with us, and Ill respond when I check back.

 

Sounds like the internals of the cat are shot.

 

A problem I had with the Camaro was it too would make this god awful 'metal on metal' sound at idle. I discovered that it was just a heat shield clipped on the top of the I-pipe that had popped out of one of its tabs. I popped it back in and the sound was gone so maybe that would be worth a check.

You could try disconnecting the I-pipe from the Cat then rev it a few hard times... see if the clanking continues and if so specifically if its coming from the cat.

If it is coming from the cat you could alway gut it out just to see if the sound is still there. If its gone then you know it was a bad cat and buy a new one. Until the new cat comes in you can just re-connect the I-pipe and have use of the car until then.

 

Another way to check the heat shield is simply put the right side of the car up and hit the bottom of the cat or part of the exhaust pipe with you hand and you can usually tell if it's a heat shield or if it's coming from the cat.

 

Alright, well right on, thanks for the tips, i'll start checking out by doing what you said and see if it is the cat now. Let y'all know later.