Robert O

I know I know.Believe me I searched and read many threads. I figured that I had it nailed down to the TCT but my efforts have been to no avail.Rattling sound seemed to have showed up following an oil change to full synthetic.So I drained that batch and replaced with semi-sythetic.No dice after several runs. Then came out the TCT and had the worm sandblasted and reinstalled.No help still after a few runs. Replaced with new TCT. No help there either. Trouble is the darn rattle is not rythmetic like valve train noise but rather much like one would think a heat shield or such might make.Anyway,went ahead and adjusted all valves. A few were off by a couple of thousanths but no big woop. Still no help. It seems really hard to track down the exact source as the sound tends to not be in one distinct location.So I layed down beside the vehicle with engine running at idle and it may be coming from the area of the cat but not real sure. I've heard tale of an inner baffle that may tend to crack or break loose within the body of the cat but can't seem to definatively conclude that the cat is the source.Even with the screw driver stethescope check.It just seems to move toward where I tend to suspect as it resonates within the engine bay and under car near the front for sure. No bolts backed off from the bell housing and all heat shields seem solidly attached.Damn this bugs me. Once the engine is warmed up and driven a bit the sound tends to disipate. Very frustrating.

So, now I'm back to suspecting the timing chain.My last effort will be to drian the semi synthetic yet again and replace with 10W30 dino oil in an attempt to at least get a reaction to see if it effects the rattle issue. Other than that I suppose if it is the cat producing this perplexing rattle at cold startup all I can do is wait for it to eventually trip a CEL. Any light that anyone can shine on this is much appreciated. Oh and the car in question is a bone stock 06' with 45,000 on the clock and is disturbingly clean in and out.

Now if Billman250 would release the top secret info on the TCT mod I suppose I could try that next. Hell I've got a spare now so maybe some oil feed port or return port revising is in order.I can't imagine anything else besides the blasting of the worm shaft that one could do.Of course then there's the size to redrill issue and all.

Note: my 06' S has had the TSB AF sensor replacement and ECU reflash as per bulliten.This was done previous to my buying it as was confirmed by a rep at Amercan Honda. Hopefully there's not a piece of the old one somewhere in the cat.

osidis

have you considered the serp belt pully or tensioner? i ended up replacing the tct for no reason.

Robert O

Yup. Already looked into that and eliminated pulleys and tensioner. I think I'll pull the cam cover again tomorrow morning and reinspect clearances and have a general looksee at the cam shaft sprockets and chain.while rolling the engine over.

Robert O

On second thought osidis,I'm gonna just pull the darn tensioner bearing and pulley assy. off and check for excessive wear. Heck I'll just change the dang thing and post an update.Thanks for your input.

osidis

let me know if this fixes it.

Robert O

Well .... removed and replaced bearing in the belt tensioner pulley. No help. intermittent rattling noise still persists at cold startup. If I was a betting man I still feel that the timing chain is culprit. Perhaps the slides and or chain itself along with its sprockets are playing a part. Just don't know.I'm really at a standstill on what to do next if anything. Any more input is most welcomed.Oh ,and I went ahead and replaced the engine oil with regular dino oil just for kicks.This was before I did the pulley bearing.If I could be sure that this gremlin rattle would not evolve into something that is going to lead to an eventual catastrophic failure of an internal component I could live with it.I'd just like to catch it early if possible. I have little confidence in the local mechanics around town ,unless I could find one that is S2000 savvy.

zeroptzero

there are several heat shields on the header have you checked all three of them ?, cold idle introduces a bit more rattle than warm idle so it is likely causing something to vibrate during that proces.

Epothon666

Any chance on a video or soundbite?

Could be anything.. a loose flywheel can even sound like a tct or out of whack valves..

osidis

wow i am really stumped. i really want to know now. and put synthetic back in your car. it comes from the factory that way.

zeroptzero

might even be a broken engine mount, though a lot of guys don't realize it until they remove them and they fall apart.