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Discussion Starter #1
Recently purchased my 05 v8 Sts check engine was showing Code P0174, bank 2 system lean. Popped the hood and removed plastic cover to find cracked boot right on top, replaced and the code went away. 2 days later (Yesterday) as I’m driving across town it starts idling very rough when stopped but runs fine otherwise. Pop the hood to inspect again no other visual problems but when I rev the engine I can hear it sucking air along the drivers side of the intake manifold. I took it in this morning to get inspected and the mechanic tells me he can’t hear any vacuum leak. And tells me it the timing chain. (Attaching a photo of the inspection) Hoping to get an opinion from someone who has experienced this before as I feel it is just the intake manifold seals but am being told otherwise. I’m no expect when it comes to cars but no dummy either. Any help or information would be highly appreciated.
32B927DD-F410-4E45-A5E1-373E1E4F7F60.jpeg
 

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Loose Intake (plenum) bolts are a common issue with the N*, have you put a socket on them? They can get very loose!
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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.......... and be careful not to crack the composite manifold. Bolt torque is only 7.5 lb.ft.

The intake manifold is the intake manifold; the "plenum" is the connector between it and the throttlebody.

Here's a pre-2005 "plenum" as referenced in the GM service manual -

Plenum 1.JPG
Plenum 5.JPG
Intake-plenum.JPG
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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The torque on the intake manifold bolts is 10 N.m of 89 lb in. Note NOT lb ft. There are 10 bolts. The tightening pattern is: center on passenger side- then center on drivers side- 1 forward on drivers side- directly across on passenger side- 1 back from center bolt on passenger side etc. Continue spiraling outward. Hope that is understandable. For perspective, I would call 89 lb in - barely snug. Over-tightening = broken bolts or cracked plastic intake manifold. Hope that is your problem. Timing chains are so much worse. Good luck.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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89 lb/in comes out to 7.5 lb/ft. Post #3, first sentence.
 

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Discussion Starter #6
Appreciate the help guys. Just finished replacing the gaskets with your help, looks like the last person to do it cranked them too hard A couple were smashed and ripped
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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Sub - You have forgotten more about Cadillac than I could ever know. It is just that my torque wrench will not go that low in lb ft.
Dom - hope that fixed your problem. Timing chains are a pita.
 

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2006 STS 1SG & 2007 STS 1SE
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Loose Intake (plenum) bolts are a common issue with the N*, have you put a socket on them? They can get very loose!
Use 10 mm crossfoot socket to tighten bolts to 90 inch/lbs. For proper use with torque wrench, crossfoot sockets should be at a right angle to the wrench handle. |____
 
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