So I drop off my truck to my local mechanic to check on a slight rattling sound from under the engine. At first I thought it was the heat sheild (if there is one??). But he told me that it is the converter. That there might be a crack in the honeycomb. Is there a way to check if the problem is the converter??? Just an FYI, the check engine light did not come on and the truck does not feel any different. ex. no hesitation, misfire. Any suggestions would be great.

Thanks fellas...

 

DIY test = rap on the cat with a mallet or your fist and listen for a rattle. A mechanic can hook-up a tester (probably a Tech2 scanner) and test the cat for correct function. I'm assuming that's what your mechanic did. Yes, there should be a heat shield above the cat.

 

I have seen several Blazers with catalytic converters that rattle because the honeycomb has come loose inside.

 

My 99 Blazer has the same noise. Just haven't fixed it yet.

 

yeah mufflers do the same thing. if it does it all the time you can start the truck (make sure its a cold start) and just climb under the truck and hold it to see if thats where its coming from. you only got a few seconds before it gets hot

 

I know the feeling. Thats how mine started out. As a little rattle. Then it turned into a big rattle. It got so bad, it was embarassing sitting at a red light sounding like the bottom end was coming out from underneath it. I got one off of a wrecked 97 and now its much quieter. Also my check engine light quit coming on. As the converter wasn't doing its job. I ended up putting new bolts in it as I had to use a cutting torch to get the old bolts off.

You could take the old one and give it a good shake and it sounds like its got gravel in it. Not a good thing.

 

mine has a horrible rattle to it, plus a few leaks in the exhaust. Plan on getting a high flow cat soon and rebuilding everything.

 

I hate to revive and old thread but I am having the same issue with our 99 Jimmy that we just purchased. The Cat is making the same noise plus the check engine light is on and the truck has a hesitation when taking off from a light and is rough on fuel. I was considering doing a tune up but after reading up here on the Forum (using the search feature) I am think replacing the Cat will be the best place to start?

The local muffler shop wants close to $400 for a new Cat but the local parts store can get us one for $195 which is a direct bolt on. Anybody have any issues with after market Cats? Does the Gen 2 Jimmy's have an O2 sensor after the Cat?

 

Getting the SES code read would be the best place to start.

 

Good point, I will do that tomorrow and report back here.