Using the Microphone with the Pico NVH

Scott from Claremont Manager Posted   Latest   Edited  
Demonstration
Tooling
Pico Technology
2001 Lexus RX300 3.0L (1MZFE) 4-spd (U140E)—JTJHF10U910232265
Engine Noise

The above vehicle was towed into the shop today with the complaint that the engine is noisey. Yes indeed this was a noisy engine with some very odd rhythms. I have the Picoscope with NVH and I’ve been looking for a reason to use the microphone and that time came today. 

Check out this short recording

Here’s a zoomed in capture where I have #1 injector triggered via channel D. I figured that there were noises associated with the firing of cylinders 3 & 6. You can see in the video where these noises cycled in and out. What do you all hear besides It needing an engine?

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Bill from Rosetown

 

Technician
 

I am not sure what I should be hearing. Is there a rattle type noise along with the knocking?

I am very interested in having a good technique to reasonably pinpoint a noise source prior to disassembly.

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Scott from Claremont

 

Manager
 

Hi Bill, 

There are two distinct noises, one that fades in and out and the other seems to appear. Channels A/B/C are stacked on top of each other which come from the NVH module with the microphone sensor attached. I doubt that we'll be taking this one apart but this is part of why I wanted to have a look. 

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David from Kokomo

   

Educator
   

Scott - sounds terrible. Might be interesting to see and hear same test with cylinders 3 & 6 deactivated.

Another simple question - 2nd in 24 hours! This question is pertaining to your pattern from channel D with #1 injector events. Specifically referring to the smaller spikes you've marked as the 6 cylinders in their firing order on the same channel; are these the spikes from COP events coupled into the injector waveform via their connections at the PGM relay / power distribution bus bar common with the injector's power feed? If so it looks like a very efficient method of getting a sync from each cylinder. Excuse my ignorance - my goal for 2019 is to increase my scope knowledge so your answer will be one step in that direction!

Thanks

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Scott from Claremont

 

Manager
 

Hi Dave,

I didn't study a wiring diagram for power distribution on this vehicle yet, however, when I saw the spikes I assumed that they were secondary hits which provided me with an additional point of reference.

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Keith from Collinsville

   

Diagnostician
   

Very cool scott, ive done similar with GM knock sensors, ill see if can remember to post a pic of my setup. One question, why use the injector signal as a reference mark?

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Scott from Claremont

 

Manager
 

The injector signal wire was the easiest to get to without any disassembly. Fortunately the secondary events were revealed within that trace. 

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