Ok, I have weird issue going on. 1998 ES300 with about 150,000 miles. Yesterday, I was driving with my kids in the back seat and my mom in the front seat and we were going up a hill in bumper to bumper traffic and then the lane opened up and I gave the car gas, the RPM went up as normal, being a full car and climbing a hill and then I noticed a rattling noise coming from underneath the car, sounds like an object in a can sort of. As I gave it more gas and the speed increased, so did the noise. Ive heard this sound before on my way up to the mountains. I never hear this sound in my daily driving. NO CEL. The only thing I can think of, is that a piece of my internal cat broke off and is floating around in the cat and under high RPM and load it causes this piece to rattle around. Thats the only thing I can think of that is under my car that would give this type of sound. I kind of had a similar issue with my old car, 1991 Nissan Sentra. Any ideas from the pros out there. Thanks for any input.

 

Probably spark knock. Are you using regular or Premium fuel??

 

I had a rattle coming from underneath my Caddy last month. Sounded just like a pebble in a tin can. The guy I bring the Caddy to said it was debris in the net of the exhaust or something along those lines and he cleaned it out. The sound hasn't come back since.

 

Thats interesting, but the sound is coming from underneath the car, like a pebble in a tin can. I use Chevron regular and I'm in California. Wouldnt a spark knock set off a CEL?

Yup, it sounds the same way, but I only hear it climbing a grade and the car full of people (underload). I had a similar issue, but it was on a 1991 Nissan Sentra. When it came time to get it smogged and it didnt pass, I replaced the Cat. Converter and inspected the original cat. converter and shook it and I could hear something rattling around inside. Once the new cat. converter was installed the rattling went away. I had a CEL with that issue, but the car was an OBDI, so I was unable to scan it and see if the bad Cat. caused the CEL.

I figured if I had a piece floating around, that it might trigger a CEL, maybe enough hasnt broken off to cause the cat. convert. to fail and set off a CEL. This is just my assumption. The car is due to be smogged next month, last year it was smogged and it passed, but the hydrocarbons just passed by 1 point, it was 1 point under the max. allowable. Everything else passed easily. I just wish I had an OBDII scanner to check everything.

 

Could it be a heat shield hanging down and touching the actual exhaust pipe?

 

The corners where the shield bolts on to the exhaust is really thin metal. About a week ago I heard something like a tin can bouncing/dragging/scraping under the car (especially over bumps) and sure enough it was the heat shield hanging on by a thread. It may be possible that yours is bouncing off the exhaust if it's not actually hanging all the way down yet...

 

Crawl underneath and do a thorough visual inspection of your exhaust system when cool. Gently shake various components to try to mimic the sound. If the cats shield is OK, and you find no loose parts I would lean towards it being an internal cat issue.

Good luck

 

Thanks guys, I thought it might be a heat shield issue, but checked underneath the car, everything is intact under there, nothing loose. I spoke with another CL member and he thinks something may have broke off inside the cat and under exteme load and RPM the piece becomes airborne and is flying around in the cat. He believes not enough has broken off to effect my emissions and thats why no CEL. I guess ultimately I will need to buy a code reader for any future CEL issues and maybe take the car to a muffler shop and replace the cat. convert. I am due for a smog check next month also.

 

If you have an AutoZone near by they will throw a reader on it for free....but having a handy dandy pocket one helps...I keep one in the trunk, helps friends an colleagues more than me.

 

Here in Calif, Autozone has told me they cannot scan for codes on customer cars, guess it is not allowed in Calif. Damn Calif, too many rules and regulations for people to do business in Calif. and they wonder why the economy is bad. Yup, would be nice to have one handy, will have to buy one off of ebay, but thanks for the info anyway bro.

 

Yep, your post reminded me of what I was interested in last summer, finding an OBDI & II scanner. If you don't need OBDI then there are a lot cheaper options available to you. I'm looking at these two,

http://www.autoxray.com/product_detail.php?pid=94
http://www.iequus.com/Product/Detail...4-9CF54CD7A757

According to the invoice from the rattle I had on my Caddy, "Drop the catalyst heat shield, blow out with compressed air all the rocks and debris in screen"

 

Marcus,

Im looking at the Innova also, but the 3130, they're around $140.00 on ebay

 

Go to Sears and buy any scanner you want. You have 90 days to use it. Return it for full refund, no questions asked. It's like an AutoZone free loaner. I bought the OBD1&11 by Craftsman. I liked it so much I decided to keep it. Cost: $299.

 

Here in WA, the AutoZone doesn't scan for the codes themselves either. I just had to give them a piece of ID for collateral, and they gave me a scanner to use myself.

 

That's a slick idea, never thought of that. Hmmmm, food for thought, thanks bro.