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I’ve got the typical m30 injector click, which sounds like a sewing machine at speed, pulls like a freight train, and idles rock steady even cold. Sounds very much a click rather than a tap, and seems to quiet in volume at speed under less load. That could be due to road noise though. Anyway - stuck my ear to the engine and the valves are are beautifully quiet, and I’m *fairly* positive the clicking injector is the 3rd from the back, under the boot between the VAF body and intake manifold. Is there any way to test the injectors to find with certainty which one it is? 

Pull the connector off and see if it goes away.  Don't leave it that way long as the O2 sensor will see the excess O2 and try to fatten it up, but just for testing it'll be ok.  Or disconnect the O2 sensor for testing it.

Use an automotive stethoscope to listen to each injector, you'll quickly find which one is off. Or a long screwdriver touching each injector and the handle held to your ear.

Bought from eBay this chinese injection tester (about usd 20 delivered in my home, to US should be the same) and it it incredible good stuff...previously I saw a youtube video where a guy in the States use this tester when he was cleaning the injectors in a ultrasonic bath so I decided to buy one. Very simple to use, just connect it directly to the car battery and to the injector you want to test (removing the plug an connect the tester wires instead)...put in position 4 (continue pulse) and you will ear the injector clicking. If there is a different or higher injector clicking sound you'll discover it.

https://www.ebay.com/itm/402244420862

In other hand, I had to replace last weekend both inlet and exhaust rocker arm eccentrics from cyl 5 (M30B34) because the high clicking noise from that cylinder. Why??...after valves clearance adjust I was pretty sure all the valves was in tolerance but an intermittent clicking noise persist in the cyl 5 area.....read a post where it was described that even you tried to adjust the clearance and you swear it is ok, the contact area of the eccentric and the top of the valve is worn enough to get a "false" adjust (I mean the eccentric is worn not the valve) ....removed the eccentrics and yes it was worn, even a small holes in the contact area....replace both eccentrics using a used ones from another M10 head (M10 and M30 use the same rocker arm) and the clicking sound is gone.....I must to replace all the eccentrics eventually.

Thanks everyone. I’ll give the screwdriver a try. Also gonna order one of those testers and give it a shot. 

thanks yall

Freight wrote: Jan 14, 2025 2:37 PM Thanks everyone. I’ll give the screwdriver a try. Also gonna order one of those testers and give it a shot. 

thanks yall