I have an 02' SE with 97k on it. Makes a bad rattle or clanking noise on the down rev around 2000rpms. Anyone know what might be the issue???

 

Maybe your precats are broken down inside. Do you have a CEL code?

 

can be loose exhaust, heat shield or crappy flex as well

 

My car was doing the same thing and it was the mesh inside the rear bank precat that came loose.dropped it,gutted it,all set now.Try to get it on a lift and have someone under the car chase the noise while you keep the rpm's where it makes the noise the loudest.

 

Doesn't gutting the cat change the exhaust noise? louder?

 

It does.Mine has the cats gutted,a test pipe,and a 3'' catback and it sounds like im running headers,noticable power gain too.you will probably need an 02 sim to shut off your cel if you decide to gut them.

 

Most likely it is the pre-cats. Worse option is the valve train.

 

God, lets hope it isn't the valve train.. still have yet to investigate the problem. Gonna gut the pre-cats next week and see if that will quiet it down.

 

I have the same exact noise. Keep this thread updated

 

Gutting the rear bank pre-cat this weekend. Will this trigger a CEL?

 

yes!
you need o2 simulator

 

Had the same rattle, was bank 1 (firewall side) pre-cat. Remove (need to order new gaskets) and inspect. If the catalyst material is loose, that would account for the rattle sound on down rev.

You can pick up the pre-cat from Nissan, discount here http://forums.maxima.org/8272195-post22.html, and be sure it'll fit and take care of the problem.

Also can get headers and the o2 simulator.

 

Might be your valves rattling. do you have an oil burning issue?

I burn oil at a good clip in my 03...come the 2000mmile mark after a change i get an obnoxious rattle from the engine bay and its the valves. Never happens after a fresh change or if i top off the reservoir.

Try checking you oil levels

 

I DO NOT want new precats lol the reduce so much power...but where can i find the O2 sim.?

 

Yeah i get that rattle too, but mine only happens about 2500 miles into the oil change, and then i just change the oil again. But this rattle is constant when motor is coming down from about 2200 rpms. Sounds like something breaking apart..

 

Only place to get them these days is on Amazon. Do not go to O2sim.com... They got shut down and apparently still take people's money but haven't shipped sims out in a long time.

 

Costs nothing to remove the pre-cats and inspect. You'll only need the gaskets but probably can take the chance and re-use them. DaveB told me people spray the copper gasket over exhaust gaskets and re-use them.

You'll know you need the pre-cats if the catalyst is loose in the housing. When I replaced my known bad pre-cat, I felt the engine respond BETTER. Then I did the other pre-cat and again noticed a slight boost.