First off when this problem had originally happened i tried out a few things. I switched to using premium (91 or 93 Octane gas) and it sill happened so I don't think this is an engine knock. Later on I heard it when I was driving and found that my cat off the y pipe went bad. Well today I had my cat removed and a test pipe installed because Im way low on money to get a new cat right now. The car once again drive like brand new however the noise is back to haunt me.....this noise occurs when reving or briefly after the engine turns over. I noticed that it went away for a while and all I heard was my catalytic converter clanking when my car got warm. Today when i turned on my car I heard it and hoped it was just my imagenation(I thought it was all the cat, but I guess I was wrong) Then when I got home I reved it and its back!

The best way to describe what it sounds like is if someone was throwing rocks in my engine. It sounds like its coming from the front and almost reminds me of the noise used in a movie when a car breaks down.

What could it be? catalytic converter and engine knock/ping are ruled out as I use a min of 91 gas and my bad cat is gone. I just really hope its nothing serious...

thanks

 

check to make sure all your exhaust is tight and no loose heat shields. When i gun the throttle on mine it would ping for spit second, i guess thats normal when its hot outside, does not do it when cold outside. Check stuff in the engine compartment to make sure there not loose. I had a loose airbox once that was making noise.

 

sounds like a loose heat shield to me...

if it vibrates you can see it most likely moving you know? have someone rev while you're under/looking at it to determine whats loose...

 

Unless you have headers, only one out of 3 of your cat's have been ruled out.

 

i checked out the other cats their fine. car drives fine. i noticed a friend with a quest has the same problem...maybe its just a heat shield as those break easy.

 

from the limited info regarding the sound...it could be a lose heat shield or a timing chain rattle.

 

i dont really now how else to describe it. I was actually thinking timing chain but only at 111k? I could probably take a video on my phone of it doing it if that would help diagnosis

 

mine started rattling at 40K

check your oil level

 

oil level checked out fine I just changed it about 2k ago so I didn't expect it to be bad. now if this is the timing chain how urgent is it to get it fixed? what does this entail?

edit: I looked up some videos of what a bad timing chain sounds like and all of them sound a lot worse then what im having. the noise isnt even similar. I think it might be a heat shield or possibly a loose air box?

 

you're prolly not getting enough oil through the engine. my old taurus used to do the same thing, when first start and during high revs. put some lucas oil stabilizer (if you use synthetic oil, make sure to use lucas full synthetic!). if that's not it, it'll at least help with cold starts this winter. $10 for normal stabilizer and $15 for synthetic @ autozone. at worst, if you have high mileage, you're helping protect your engine.

 

what do i do with this stuff just pour it into the engine where the regular oil goes? and yeah i do use Mobile 1 synthetic. Also does it matter if it starts doing it at a particular rpm range? I think if I pass 2 then it will generally do it and keep doing it until I let off the gas. it generally happens right after the car turns over but has been happening less. It never does it while driving either just when in park/neutral

 

it probably does do it while driving but you likely just can't hear it at highway speeds. you put it right in the engine but it has to be a certain ratio, 1 part stabilizer to 4 parts oil. my 95 has a 4.5 qt capacity. so i drained about 3/4 a quart and put in a little over half a bottle of the lucas. but make sure you use the "full synthetic". it has a blue label and it's about 5 bucks more. my max was starting to do that rattle too, it's at 160,350 miles, and when i put the lucas in it the sound was GONE!

 

thanks for the good info man. Ill pick some up. I might have my friend put it in becuase im not too good with these ratios and stuff lol

 

After looking at a bunch of videos on you tube it seems like my problem sounds most like some sort of an exhaust rattle. Maybe I should take a second look at those other two cats

 

cool. definitely check to be absolutely sure what it is. but like i said, it doesn't hurt to help an aging engine. besides, spending 15 bucks and possibly fixing the problem sure beats paying a diagnostic fee at a shop. btw, if you do go the stabilizer route, double check your owner's manual for your oil capacity just to make sure you drain and replace the right amount. good luck dude!

 

drop your y-pipe and visually inspect your precats! Sure it's not detonation? Filling your gas pass the auto shut off limit can damage your charcoal canister which can man your car detonate lightly at part throttle......

 

I checked under the car and saw that the front cat was leaking and shimmying a bit when I hit the throttle, sounds like I found the problem. Just curious as to what the hell the leaking was about. I saw a drop fall then it looked like it was burning what ever else came out.

And I never knew that filling past the auto shut off could be dangerous. I do it every time....dam

 

yeah, it can damage the charcoal canister like cmax said. also, always make sure you turn the gas cap till it clicks a few times. on some newer vehicles with the pressurized fuel system if the cap doesn't seal correctly it'll trip the CEL and you'll have to pay to get it cleared.

 

yeah I know to click it. Well looks like im getting a new catalytic converter...luckily its the cheaper of the 3 to replace. Maybe ill get a cat back now. I love those greedy evo II exhausts