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knock sensor help

MADpa2006

Full Member
Joined
Nov 16, 2013
Messages
34
 
:needhug:

Dagnabit - after getting my tranny leak fixed at the shop check engine light came on.  Bought a code reader (always wanted one of those) and it's the dreaded knock sensor low voltage code. 

Now, I've never taken apart any portion of an engine, but have been reading posts and watching videos - thinking about trying it myself.  New challenge and I like to learn new things.  So, gonna start early one morning and hopefully get it done without having to find a mechanic on Craigslist to come and bail me out half way through.

I have a few questions:

  • I am worried to death about something falling into those intake ports, but will definitely feel the need to make that whole area squeaky clean before I reassemble.  My thoughts are to scrape away the gunk on the edges of each port as soon as I get the thing exposed, then tape over them with masking tape.  Thoughts?
  • What should I use to clean the manifold area?
  • It seems that you have to order a GM knock harness from the dealer but I see a Dorman one on Amazon that I can get deliverd with the knock sensors....anybody know of any issues using Dorman harness vs. AC Delco?
  • I see some folks using GM gasket and many using Fel-Pro...opinion on which is better?
  • Besides a wrench that provides exact torque settings, any other special tools I'll need besides the RTV sealant?

There likely may be more questions as I psyche myself up for this, but these will at least get me the parts ordered.

TIA
 
Get some good quality paper towels...I use those blue shop towels.  Stuff them down inside the ports while you scrape stuff off.  Use an air compressor and gently blow the debris away.  You will probably want to cup your hand over the nozzle to control the airflow.  You don't want much more than if you were blowing it yourself...but not get dizzy and fall out.  Then take a little diesel and a medium-stiff brush and gently scrub the surfaces.  Wipe dry and then use painters tape...you don't want any glue being left behind.  The gasket on the intake can be reused if it isn't damaged or crushed.  Make sure you check you torque and order pattern spec's on the intake.  I might have it on my computer somewhere still...I'll look, otherwise you'll have to do a search.  A basic set of mechanic's sockets should get the job done.
 
MADpa2006 here is some post for you I hope they help.
The knock sensors were my first major under taking on my Avy.
On the intake gaskets there was an update. I do not know if there is a year GM installed them. You can not go wrong with Fel-Pro I used the updated premium from Fel-Pro when I did mine. There are some things I stick with OME and the sensors and harness is what I did. 
Get the metal fuel line tool. As ms38w stated be very specific about the sequences and torque you will see them in Sperry Tech Center. I made copies of the steps need so I would have them with me and not have to go back and forth. I keep all what I copy in a binder.
Good luck keep us posted and ask away.

http://chevyavalanchefanclub.com/cafcna/index.php/topic,44372.0.html
http://chevyavalanchefanclub.com/cafcna/index.php/topic,136793.0.html
http://chevyavalanchefanclub.com/cafcna/index.php/topic,119754.0.html
http://chevyavalanchefanclub.com/cafcna/index.php/topic,125696.0.html
http://chevyavalanchefanclub.com/cafcna/index.php/topic,71618.0.html

 
There ya go.  An "Administrator" would have said something like..."this topic has been covered extensively here...learn to use the search button...blah, blah, blah..."




(y) Just having fun.





no administrators were harmed in the making of fun for the purpose of this program...
 
Thanks all - did read most fo those forums and even some over on the GM-Trucks forum but didn't see any specific answers to my questions listed above.

One of the big reasons I'd like to do this myself is to make sure everything gets cleaned up in there the best it can - I bought this truck last year with 136k on it and I know it was pulling duty out west most it's life in Wyoming & New Mexico.  The thought of taking it to a shop and having them do it - I'm just not sure they'll take the time to clean things up and be extra careful not to let debris get down those intake ports...call me paranoid or skeptical, but I've not had good repair experiences at shops with this truck yet.

 
More questions not addressed in other posts - again, pardon my ignorance, but i am not a mechanic, though I am somewhat technically inclined...just no experience with engines (yet):

1.  Is there anything special I can do to prevent dirt/debris from falling/getting into the intake ports when I remove the intake manifold?  Other folks doing this job indicate acorns, mice nests, etc. under there.  Again, super concerned about stuff falling into those and causing deeper issues down the line.  Shoot, had I known this knock sensor deal I would have bought an 07 after they moved them!

2.  These foam spacers everyone is talking about removing and junking - where are they?  between the intake manifold you remove and the sensors?  If so, anyway to get them out before removing the manifold and getting a vacuum between there to remove debris before exposing ports?

3.  How does one manually turn the engine so as to close the ports for a real good cleaning of the intake ports once exposed?  Once I start manually turning the engine to close these ports is there an expected sequence to them closing (will be hard to tell which one os clsoing if I have rags stuffed in all of them !!!)

Thanks
 
MADpa2006 said:
I'm just not sure they'll take the time to clean things up and be extra careful not to let debris get down those intake ports

I cannot speak for all mechanics - but I go the extra mile to pre-clean, clean, and post-clean (as best as practical - I'm on your dime ... ). If the motor is exceptionally clean, I make it cleaner than when it came in. If the motor is nasty - I clean it enough so I can remain as clean as possible. IE: The more you care, the more I care ;)

Every mechanic is (or at least should be) concerned about the ports - though some more than others. It's not the end of the world if something falls in them. Metal can be retrieved with a magnet - other large debris with needle nose pliers / shop vac. Anything that slips past the valves into the combustion chamber can generally be retrieved via the spark plug hole.

MADpa2006 said:
1.  Is there anything special I can do to prevent dirt/debris from falling/getting into the intake ports when I remove the intake manifold?  Other folks doing this job indicate acorns, mice nests, etc. under there.  Again, super concerned about stuff falling into those and causing deeper issues down the line.  Shoot, had I known this knock sensor deal I would have bought an 07 after they moved them!
Use a compressor and air wand to blow off the engine before removing anything. As you remove parts, blow off the engine again. After pulling intake, like ms38w said, plug the ports (on the head - not the intake itself) with decent shop towels. Do your cleaning. Then before your done, blow off / vacuum the top of the engine and ports before pulling the towels out. I personally like to take a shop towel wad it up to the size of the port, then take another shop towel and and wrap it around the wad (as to have a smooth surface) and stuff it in the port with the smooth side up so I can see if any debris in around the towels before I pull them - I'm just anal like that though.

Don't over stress about debris falling into the intake. Stuff like dead bugs, dust, etc. will not hurt anything falling into the port. Stuff like acorns, nuts and bolts, or other hard or incombustible material could cause problems. Like I said, you should be able to retrieve anything with a magnet or needle nose pliers and or a vacuum.

MADpa2006 said:
2.  These foam spacers everyone is talking about removing and junking - where are they?  between the intake manifold you remove and the sensors?  If so, anyway to get them out before removing the manifold and getting a vacuum between there to remove debris before exposing ports?
You will see them when you remove the plenum. Leave them or toss them - it's up to you.

MADpa2006 said:
3.  How does one manually turn the engine so as to close the ports for a real good cleaning of the intake ports once exposed?  Once I start manually turning the engine to close these ports is there an expected sequence to them closing (will be hard to tell which one os clsoing if I have rags stuffed in all of them !!!)
There is a big pulley on the front of the engine, centered at the bottom. Inside the pulley is a large crankshaft nut. Use a breaker bar and socket and you will be able to turn the engine over by hand. Always turn the engine in a clockwise direction. You won't be able to close all the valves at one time. When one valve is closed, another will be open(ing). The Firing Order is 18726543. Cylinders 1357 are on the left bank (drivers side). 2468 are right bank (passengers side). #1 is closest to the drivers headlight #7 closest to drivers seat, #2 is closest to passengers headlight & #8 passenger seat. If you remove the spark plugs it will be easier to turn the engine by hand.

Intake ports generally don't need "cleaned".

Tip: use Brake parts cleaner to clean the engine with - unless your in California, in which case you will likely get cancer ;)
It evaporates quickly and does not leave a residue behind. If you are not used to it, it will burn/tingle your hands - use rubber / latex gloves just don't expect them to last long once doused with it.

Check this video out. I didn't watch the full thing - just skipped around - but it seems to be accurate.
https://www.youtube.com/watch?v=872jlCs2ECQ
 
Apocalanche ,

Thank you for that detailed reply - I greatly appreciate the info and wish I had such a warm fuzzy feeling about the quality of work of my local mechanics I've worked with compared with your obvious care and pride.

Two additional question - when you say the intake ports don't need cleaned, I've seen many photos on here whee there was significant 'soot' buildup - I imagine with 141k miles, mine are pretty built up...no need to get that out?

Second follow up - as for cleaning the intake manifold once removed, if it still has all the injectors and fuel rail attached, I assume it will be difficult to do this?  And, if I can clean the manifold, is there any special manifold cleaner to use since this is a composite manifold?

Thanks again
 
MADpa2006 said:
when you say the intake ports don't need cleaned, I've seen many photos on here whee there was significant 'soot' buildup - I imagine with 141k miles, mine are pretty built up...no need to get that out?

Well, theoretically (and in a perfect world), there should not be any soot build up unless your intake valves are not closing all the way - or your exhaust (cat) is plugged not allowing all the gas to escape. That being said, you can clean them if you would like. I'd suggest a toothbrush. Here's the deal though. If you use cleaner inside your intake ports on the head, the excess will go into the cylinders and seep past the rings into your oil. Too much solvent in the oil is a bad thing - but a quick oil change will take care of that. How much is too much? hard to say.

Unless there is excessive build up, it's probably not worth messing with. I don't "polish" the ports unless I'm working on the heads on the bench.

MADpa2006 said:
Second follow up - as for cleaning the intake manifold once removed, if it still has all the injectors and fuel rail attached, I assume it will be difficult to do this?  And, if I can clean the manifold, is there any special manifold cleaner to use since this is a composite manifold?

Injectors are held into the manifold by rubber "O" rings. They can easily be "popped" in and out. If you do remove them, dab your finger in a bit of fresh engine oil and run it around the o-rings before reseating the injectors. It will help them reset easier and not tear up the o-ring.

Brake clean will be fine on the intake plenum. I've owned an LS1 and LS6 and used a couple cans to clean the motors - plastic and all.
If you use it in the throat of the throttle body, just be sure to lightly relube the throttle plate pivot points. Be careful with the gizmos on and around the intake - they can be pretty pricey for such small items. Just about every orifice on the intake is connected together - you spray it in one - it's going to run out another.

Brake clean can/may discolor plastic (which can be restored with some light oil) but is generally ok to use on just about anything under the hood. Dawn Dishsoap, Gasoline, Diesel, Kerosene, WD-40 and a whole host of other commercial cleaners can be used as well - some say avoid plastic, some say plastic safe. What you use depends on how much elbow grease you want to apply.

The weather here just rose above frost-bite so I'll be bouncing in and out the rest of the day. If you have any other questions feel free to ask.
 
Alright, I think I've confused myself watching too many You Tube videos on this.  I'm going to tackle this Thursday - I have ordered all necessary tools I could possibly need and have to pay the stealership for the OEM harness (Though have had no problems with other Dorman stuff, didn't want to chance this; could have gotten through GMPartsDirect but only save $12 after shipping with no certainty of when it would arrive..)

I do think I am pretty familiar with the various components attaching to the manifold.  Can someone who's done this or is familiar give me exactly what I need to take off to remove the manifold assembly as a unit (fuel rails attached, etc)?  I want to be able to pull it off so I can clean it good and have unfettered access to the head, but don;t want to take off anything otherwise necessary...
 
The harnesses on the injectors are kind of a bugger.... you have to slide up the gray part first then they will come off.... there is a large wire harness that crosses over the top of the intake which you just have to make sure all the ends get reconnected. If it was me I would also get throttle body cleaner and whatnot since you are already going to have it apart... it didn't make sense for me to do the knock sensors then take it back apart to do the throttle body a week later :beating: But you seem to be on the right track  (y)
 
I just did this myself, and made a tutorial video on how to do it. I cover everything step by step as well as any special tools you will need.


Here is the video I made, I hope that helps you.4.8 5.3 6.0 knock sensor replacement GM: http://youtu.be/0ynkoOhU9BY
 
Dialn911 said:
I just did this myself, and made a tutorial video on how to do it. I cover everything step by step as well as any special tools you will need.


Here is the video I made, I hope that helps you.4.8 5.3 6.0 knock sensor replacement GM: http://youtu.be/0ynkoOhU9BY

Haven't watched it yet, but 23 minutes...whoa, looks like it is going to be magic!!  Just wish I had your weather up here.  Can;t wait to watch it and, once I get a break i the weather and schedule, actually do mine myself ...  All the parts and tools are just sitting here ready to go!!

Thanks Dialn911    (y) (y) (y) (y) (y)
 
no problem, yeah the weather here is nice.  too bad the real Job doesn't take 23 minutes! ;)

I hope it helps, let me know. If you have any questions hit me up.
 
I do have a general question...if I am going to remove the injectors, should I clean them? 

I already know I'll spend an entire day doing this as I have serious OCD issues and I want to make sure I do everything I can to fend off future issues and enhance performance/mileage etc.  The truck is getting up there - 142k miles and I just recently bought it...have no idea what's been done to keep it healthy in the past.  But I really love the truck and want it to stick around a while!

Oh yeah, what about the throttle body?  Should I look up how to clean that while it's off?

Thanks
 
You will find its so easy to remove the injectors and throttle body, I would focus on getting your truck put back together and running Before the smaller stuff.I sprayed mine down with carb cleaner and cleaned them out, but I didn't go through a complete cleaning.

it's probably not necessary, but you can if you like. it wouldn't hurt.
 
wyotonka said:
Anyone know where to get a replacement intake bolt? I managed to snap one yesterday re-torquing mine  :E: :E: :beating: :help:

That's pretty scary - did you have a torque wrench and have it set right?
 
well, I hope I have the one and only torque wrench I'll need...it 20-200 inch pound range and a dual readout for newton-meters (2.26 - 22.6) - I read on the tech sheet that 5 Nm = 44 lbs-in and 10 Nm = 89 lbs-in.

If anyone thinks I won't have the sensor and manifold bolt torques covered, let me know
 
MADpa2006 said:
well, I hope I have the one and only torque wrench I'll need...it 20-200 inch pound range and a dual readout for newton-meters (2.26 - 22.6) - I read on the tech sheet that 5 Nm = 44 lbs-in and 10 Nm = 89 lbs-in.

If anyone thinks I won't have the sensor and manifold bolt torques covered, let me know

200 inch-pounds is only 17 foot-pounds.  I'm not sure if you'll be running across anything needing more torque than that but 17 foot-pounds isn't very much.  That's why I've got 2 torque wrenches.  :D
 
enoniam said:
200 inch-pounds is only 17 foot-pounds.  I'm not sure if you'll be running across anything needing more torque than that but 17 foot-pounds isn't very much.  That's why I've got 2 torque wrenches.   :D

tech Bulletin I read says:
Knock sensors:  Tighten to 20 N?m (15 lb ft).
Manifold bolts : Tighten the bolts a first pass in sequence to 5 N?m (44 lb in);  Tighten the bolts a final pass in sequence to 10 N?m (89 lb in).

Wrench I bought has 2-22 Newton meter range, so I think I'm okay? All these lbs in; ft lbs, Nms...so confusing.  So, the knock sensors get tightened more than the manifold bolts it sees...not sure that makes sense, but what would I know  ???


 
yup you should be fine. The reason the manifold bolts  are less tight is because they are dispersing the pressure over a vast area. Manifold doesn't need to be tightened very much on each specific bolt. Knock sensors can be touchy, so make sure you set them ta 15 foot pounds. Too tight or to lose can throw off readings.
 
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