Sputtering Noise after 4kRPM

magnnum_paul said:

The first thing that came to my mind was something related to the VTEC but the K20 engine has VTEC engaging at 5800 RPM. This sound only happens when the engine is engaged to the wheels via the transmission or when coasting in neutral as well?

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bakumar said:

First you need to identify whether the noise comes

1. Only when you are driving and in all the gears - It maybe related to the transmission and you need to check the wheel bearings, drive shaft, gearbox, steering box and the differential.

2. Even when the car is parked and revved above 4000 RPM - it maybe related just to the engine and you may need to check everything related to the engine from the ignition timing, plugs, rings, etc.

Also suggest that you check and confirm if the noise comes with the AC both on and off.

Based on your inputs we can try to narrow down the possibilities and identify the cause.

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bakumar said:

Heat shield rattle is quite easy to find and fix and it maynot be the problem your case.

Exhaust leak due to cracked header would usually set off the O2 sensor code.

The other possibility you can check is the exhaust system. Please check if any of the weld points on the pipe gave in and the pipe is rattling against the underbody. Especially the muffler which hangs by a rubber boot.

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magnnum_paul said:

R18 VTEC has economy and normal cam, teh economy one being on between 1k-3.5k RPM and loads below 70% aprox.. Bakumar's advice is good: you want to pinpoint the system that is malfunctioning, since it only happens when accelerating and in gear it could still be the engine or the transmission since some problems occur only when the tranny has load on it. I'm affraid I can't give any more advice Keep narrowing down when and how the noise appears and that might give more clues about what it might be.

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bakumar said:

Not the intake but checking the exhaust manifold. Usually we've the exhaust outlets coming out separately from each cylinder but in the R18A engine, there is only 1 exhaust outlet from the head.

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stvn.00 said:

when you hear the sound, does it sound like pop rocks? (metal clinking when accelerating) May be pinging. Could be your knock sensor, spark plugs or your gas.

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