Mods: Can you please change the title to "Strange sound from engine when cold and in reverse" Thanks!

Strange sound.

It sounds like a rotating metal part on metal part. At engine RPM.
Cold startup is when it usually does it.
It happens most when I put the car into reverse and load the engine.
Taking it out of reverse ends the noise.
I can wait ten seconds and do it again and the noise does not return.

It also does it when I drive and turn into a dip, or sometimes go through a deeper dip. Again, only when cold.

I'm thinking spinning metal (RPM) to metal interference issue that is worse when the engine is dead cold.

An additional clue is that if the suspension is loaded, like with three passengers, the sound can happen when warm when accelerating moderately or more. I'm thinking powertrain orientation to the chassis. Or just the powertrain to itself.

I've looked and looked in the engine bay and can't find any potential clearance issues or signs of rubbing.

I'm pretty sure it's a rotating engine piece that is hitting another part because the sound seems to be at RPM. Nothing else is spinning fast at all (driveshaft, wheels, etc).

My suspicion is the flex plate but I don't know why I think that.

Weird.

 

could be the torque converter dust cover and also check the crank damper to make sure the outer ring has not came loose to rub the timing cover.Maybe torque converter going bad ?-look for metal sparkles on tranny dipstick

 

A/C compressor clutch, busted catalyst in the converter, e-brake cable out of it's guides... Could be anything. Try to localize the sound and narrow it down.

 

probably is e-brake cable rubbing on driveshaft..

 

So it can't be anything on the roadspeed side of the powertrain since it will do it sitting in my driveway, especially when I pop it into reverse upon a cold startup.

I drove the car around a bunch yesterday and noticed that the engine definitely loses "power" when the sounds comes in. I am now going to look at the large diameter spinning stuff like the flex plate. If that thing interferes hard on the bellhousing (or starter?) that could really slow the engine RPM down quickly. Hmmm. I do have a hi torque starter. Wonder if that's hitting.

Now that I thing about it, if that flex plate is broken (or a little loose?) putting the car under load would cause it to warp and rub. Also, taking a big dip or turn, the torque converter is heavy and spinning. It could bend that cracked flex plate enough to interfere with the starter or something else. Hmmmmmm.

 

I've tested it more and I'm pretty sure it has something to do with the flex plate, torque converter, or starter. It is definitely an RPM related scraping sound coming from under the car (not the front). It only happens over big bumps and/or higher G turns (torque converter is heavy and spinning). My money is on something down there. Any experience with something like this? I have not yet inspected down there but I will next.