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Old 12-28-2019, 10:47 PM   #15
Stomachbuzz
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Quote:
Originally Posted by isaiah990 View Post
The metal rapping sound is what I’m trying to figure out, I thought it was part of the misfire
-I’ve swapped coil packs and the misfire remains on cylinder 4
-cylinder misfire occurs constantly after 15 seconds when idle rpm drops on cold start
-When I unplug coil pack #4 right after I start the car it causes it to stall. When I unplug the same coil pack after the misfire occurs or 15 seconds after start it has no effect on the idle
Could this noise be a failing injector?
I'm fairly confident that metal rapping sound is not from the engine itself. That would be an extremely alarming sound to come from the engine core.
Almost certainly from a belt-driven accessory or pulley.

...unless your valve spring broke...
I notice you have 2013 FRS.
A broken valve spring or non-operational valve would explain pretty much all of these symptoms.
Wouldn't quite explain the whole 15sec thing though.

At this point, I suppose it's pointing more towards an injector issue.
I guess make sure there isn't an injector plug loose.

Again, not trying to be vague, but these audio/video diagnoses suck with the poor audio quality. Very hard to determine exactly where the noise is coming from. Like higher, lower, left, right, etc.

Why don't you use a stethoscope or long screwdriver to determine more specifically where the noise is coming from
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