I’m getting ready to take the car to the CHP this week for its VIN and the engine just developed a little tick. It seems to come from the 1-2-3 bank and perhaps is near the front (chain side) of the engine. A few different people have listened to it and we generally think that’s where it’s from, but we aren’t 100% sure either. I have no clue what it is, but here are a few thoughts:
- If you watch the attached video, it is 21 seconds long and there are 36 or 37 ticks in it.
- 36 or 37 ticks in the video means 103-105 per minute
- The engine idles around 1250 RPM. I know it’s bouncing a bit in the video – the idle hasn’t been tuned to dead perfect yet.
- 1250 RPM means around 208 strokes per minute per cylinder, specifically 104 strokes of each type per cylinder per minute
So the strokes per type per cylinder lines up with the tick frequency. I don’t know if that’s by chance, but it seems oddly related. Any thoughts on what this could be?
Tim Trampedach's Blog 
blockquote, div.yahoo_quoted { margin-left: 0 !important; border-left:1px #715FFA solid !important; padding-left:1ex !important; background-color:white !important; } Sounds like a rocker arm in the valve train or AC compressor . Pull the belt off front and run it and see if noise goes away.
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The car actually has no AC compressor and it’s an overhead cam. Interesting extra data point: when I crank the engine without firing, the noise isn’t there.