Secondary Air Injection Check Valve Missing?? - Page 2 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > Air Induction

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Old 05-01-2019, 04:19 PM
John in RI's Avatar
John in RI John in RI is offline
2005 BowTie TrailBlazer LT
Olympic White '50U' 4.2L I6 4X4
Join Date: Aug 2018
Location: Greene, RI
Posts: 104
Originally Posted by lab2370 View Post
Thanks, I do search the forum instead of just asking blindly for help hence how I found this thread from 3 years ago instead of just starting a new one. If a problem or idea is brought up in a thread though its fair to ask about it right there to the person who brought it up. I do appreciate the response though.

I also do get all your obvious remarks, but the fact that you also mentioned it is sometimes factory installed and other times certain ones simply don't have a SAIS has me thinking of a number of possibilities.

But the biggest thing that confuses me is that this is a milled aluminum block. If as you say its done to as a bypass then it's a factory created band-aid that will trigger a check engine light always so that doesn't seem like something that would actually be done. If this is an at home bypass to just drive the vehicle it seems like it would be a rough DIY plug or something installed there. Not a machined factory created part?

Or better yet why even remove the faulty check valve to begin with? I dont think a bad check valve is going to keep the car from driving, just going to cause a light, so why would you go out of your way to remove it and replace with a plug if the light is still going to be on?
Here is a picture of the block off I pulled off a 2006 ( I thinik is was an 06 anyway ) :

When the SAI system, fails in my 05 I'm going to install this factory block off. No. I didn't cut A "rough DIY plug or something",... it's a DIY modification using factory parts. I could have cut a piece of metal to make a block-off but why bother when it took 2 minutes to unscrew the factory block off from a junk truck ?? The SAI was not used on the early GM360, they GM engineered it into the 04-05, but re-engineered the I6 engine again without SAI after finding it to be a flawed system; seems to me to be pretty easy to understand.

Maybe the original SAI solenoid was causing the truck to run crappy because it was always stuck open - or because it was stuck fully closed, maybe it was physically broken causing an exhaust leak. Your asking questions that only the PO can answer,.... and that have no relevance anyway. You've got a SAI check engine light and need to fix it for inspection. The block-off installed on your engine might as well be a failed solenoid - your still dealing with the same issue.

Like I said: when dealing with your SAI problem you've got options,

1) leave it as is and fail inspection,
2) replace missing/bad parts to clear the code
3) re-program your PCM not to check for SAI operation.

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