Grinding from Engine
 

I have a 2005 Grand Touring RX-8. Recently after I start the car after it has been off for at least 2 hours there is a metal on metal grinding sound coming from the engine. The sound goes away after about 2 minutes when the engine seems to kick into a lower rpm and idle. Any ideas on what this might be?

Air pump..disconnect it til you replace it ;)

I concur. I presume the noise doesn't change frequency with engine speed?

No frequency change with speed, just the start up thing. Thanks for the info.

Easy diagnosis...unplug the airpump power at the passenger side strut top....and see if it stops :)

Does this sound happen primarily while at or near WOT? I don't really get it during 'normal' driving, but get it every time I'm above 2/3 throttle and frequently when engine braking. I should note that it does not change in pitch, but its more likely to happen under those conditions. I'll try unplugging it tomorrow. Actually, I guess I'm frequently above 2/3, so it does show up during MY 'normal' driving conditions.

I've been thinking it might relate to my clutch since my wife's car was making a similar sound before it disintegrated, but hers had a severe loss of power while mine does not. Any ideas?

i need more inf.

If your air pump is bad I can sell you mine.

Unplug it and find out.

Well I unplugged the air pump and took her out on the highway. No change. I did notice that the sound started at around 5500 RPM, never in first but always in second gear and above.

What I find odd is that it doesn't make the sound when in neutral or first gear. I can't really tell if it is doing it in sixth due to road noise at that point.

I have a Racing Beat cold air intake (without the extra down-spout type air flow funnel) and cat-back exhaust. Both have been on the car for well over there years. I did have a minor parking lot incident where I backed into a concrete curb (didn't see the freaking dip right in front or I'd have cleared it) and bent the exhaust, we bent/realigned the exhaust but had to cut away a center section and weld a new unbent piece of pipe in. Welds all look great and no damage appeared around the cat or exhaust headers.

Coils and plugs were changed recently. Cat is fine, had it checked recently. I use 91 (SoCal) octane premium, doesn't matter on brand, all have same result. The clutch feels fine except for reverse, the shifter occasionally stops when it is almost engaged and gives me the grind and tug (which sounds like a fun activity until you realize its your clutch and thus sounds expensive).

I'm also reading the rought noise during moderate acceleration, Rattle On Acceleration!, and More "Marbles in a Can" Observations threads.

On a (possibly) unrelated note, I just had the car into the dealer for some PCM troubles. Seems that I had an intermittent code that means CAN/PCM failure but they couldn't fully diagnose. So they said drive it around some more and if it fails again we'll know more...

Not really sure where to post this now as I'm not sure if its grinding, rattling or "marbles." Crap, what was my kid doing? Tossing marbles in my engine? Timeout time!

And now I'm reading Transmission Issues.

Do you premix? I was having a similar issue, and premixing seems to suppress the problem. The only times I've had it come back were when I ran out of 2 stroke oil and had to run a clean tank of gas.

I know this probably implies there's something wrong with my OMP injectors, and oil usage is down lower than a quart of oil every 1k Miles. I just hope I'm not doing irreparable damage and that the premixing is fixing the problem in my head and I don't have a serious issue here.

nahh- the OP and this labop person are two different individuals. but labops interest in this thread is strange considering the op was talking about cold start idle noise

the problem was more obvious than I thought - thanks for straightening me out, lol