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Hey everyone,

My 98 civic dx, manual trans has 115k, purchased May '08 with 94k. Lots of highway miles!

I've been experiencing a loud unpleasant noise on gear changes, and acceleration, when the car is cold. Took it to a mechanic several months ago and he couldn't duplicate the issue, suggested possible carbon buildups and that I run at higher RPMs while driving in the city.

Two noises:
1) When car is started cold, distinct metallic rattling from under hood that increases or decreases with acceleration. Most noticeable in higher revs near shift point. Goes away quickly.

2) When car is cold, right after shifting while accelerating, a repetitive metallic clicking noise is heard. Very hollow and higher pitched. Noise intensifies with acceleration, but is not at a constant rate (does not directly relate to engine speed like noise #1). As car increases revs, noise subsides. Worse when going up hill and with quick acceleration, most noticeable in lower gears. Always happens right after shifting; after noise has subsided, sudden accelerations in gear do not create the noise. Noise goes away after car has been driven awhile. **Taking extra care when releasing the clutch seems to lessen the occurrence of this, but I can't always baby it in downtown traffic. Could it be a gas/clutch ratio thing? Clutch is older but doesn't seem to be slipping. MTF levels and fluid quality OK, according to mechanic.

Both of these noises are worse the lower outside ambient temperature is.

I need this car to last for a few more years. I change my oil regularly, as did the previous owner (maintenance records to prove it). Recently had the car smogged and the HC readings were within limits, but high; spark plugs have approx 20k on them. No CEL or other warning lights. Otherwise, performance of the car has been fine. Car has been just a little shaky at stoplights lately.

Sorry for the long post. Basically, I need to know if this thing is safe to drive - mechanic didn't seem too concerned, but I'd much rather try to afford a repair than a new engine right now. Should I get a 2nd opinion? Thank you for your help!

 
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My civic has something very similar that I can hear when the engine is very cold. The noise goes away once the engine is warmed up a bit (usually about 1 or 2 miles later).
My car currently has 235,000 miles on it, but I put in a "newer" engine at the 215,000 mile mark. The current engine and automatic transmission now have 100,000 miles on them.

The first motor had a badly cracked exhaust manifold that had a nasty rattle under harder acceleration. Check your manifold for hairline cracks if you get a chance. It's a pretty common problem.

I have no idea what the current rattle is since I swapped out absolutely everything. I even put in all new motor mounts while I had the engine and transmission out. Those sure seemed to make a nice difference in the overall feel.

Well, I'm confident that as soon as the really cold weather is gone, my rattle will go with it.