NPP Valve Squeak

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Aug 29, 2022 | 10:53 AM

MarZZ

Thread Starter

Racer

Joined: Jun 2021

Posts: 361

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From: Gwinnett County GA

NPP Valve Squeak

At around 6000 mile I started hearing what sounds like a rusty swing on acceleration. I changed drive modes while in the garage and have determined it is the NPP valve on the driver side. My question is under acceleration in Z mode with the exhaust set to loud should the valve be moving constantly? I can hear it over the road noise and radio with the windows open and it sounds like it is opening and closing constantly. I assume that at some point the contact point will wear and stop making noise but I dont want to ignor it if there is a valva control problem. Any advice would be appreciated.

Last edited by MarZZ; Aug 29, 2022 at 11:07 AM.

Aug 29, 2022 | 11:23 AM

RKCRLR

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Joined: Aug 2016

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From: Garden Valley CA

Quote:

Originally Posted by MarZZ

My advice - take it to a dealer while under warranty. Make sure you know how to replicate the problem for the tech or service writer. I know going to a dealer can be a PITA but it is your best course while under warranty.

Aug 29, 2022 | 12:51 PM

Red Mist Rulz

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I had a similar problem on my C7. Took it to the dealer, and there was a TSB to lubricate the valve. That didn't actually stop the noise immediately, but it did go away over time. The valve motors are controlled by a PWM (pulse width modulation) control system, and it seems the valves do move quite a bit, even when in track mode. I don't understand why, though.

Aug 29, 2022 | 12:58 PM

Ken_C8

Melting Slicks

Joined: Jul 2005

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From: Boston

St. Jude Donor '09, '21

I have recently noticed the same noise on my 2020 with 8,000 miles. I was in my garage changing drive modes and sure enough there is a little squeak, chirpy sound.

Aug 29, 2022 | 01:44 PM

MarZZ

Thread Starter

Racer

Joined: Jun 2021

Posts: 361

Likes: 234

From: Gwinnett County GA

PITA is correct. It took my dealer all week to change oil and add trans fluid. I asked about the squeak and they said they had no idea. I'll take it back toworrow and replicate it for them. Thanks for the advice.

Aug 29, 2022 | 02:30 PM

JerryU

E-Ray, 3LZ, ZER, LIFT

Joined: Sep 2007

Posts: 35,018

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From: NE South Carolina

Quote:

Originally Posted by MarZZ

At around 6000 mile I started hearing what sounds like a rusty swing on acceleration. I changed drive modes while in the garage and have determined it is the NPP valve on the driver side. My question is under acceleration in Z mode with the exhaust set to loud should the valve be moving constantly? I can hear it over the road noise and radio with the windows open and it sounds like it is opening and closing constantly. I assume that at some point the contact point will wear and stop making noise but I dont want to ignor it if there is a valve control problem. Any advice would be appreciated.

Hmm in Z Mode set the way it came, Power Set to Track it will NOT go into V4 and the valves will never close. If you're not sure how it is set, when you hear the noise put it Track Mode and for sure the V4 valve will stay open.

Note, there is an adjustment on the link that attaches to the V4 valve. Have not heard anyone say they messed with it. It's a stepping motor that turns the rotating lever that moves the link that turns the valves (sounds like a nursey rhyme!) Guess it could rattle!

Aug 30, 2022 | 11:06 AM

MarZZ

Thread Starter

Racer

Joined: Jun 2021

Posts: 361

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From: Gwinnett County GA

It's not the AFM valve. I never even see it go into v4 mode. It does squeak moving through the drive modes at idle in the garage so I think it is the NPP valve.

Dec 21, 2022 | 11:07 AM

MarZZ

Thread Starter

Racer

Joined: Jun 2021

Posts: 361

Likes: 234

From: Gwinnett County GA

Update. I took it to the dealer Last Friday to let them hear it. Which the service writer did and said the tech will have a look. I was told it would take a few months to get the parts on a previous visit, so I had low expectations as to when it would be fixed. The tech came out and looked at it and said it would need a whole new exhaust, I have one in stock and can have it done by end of day. Imagine my suprise. The squeak is gone and it actualy sounds better then it did before.