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haz 12"s!
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Discussion Starter · #1 ·
I had the dreaded number 2 knock sensor fail and thought it would be interesting to take some pics. The truck is stock with the exception of a catback and 87k miles and it looked it.. lol

Heres what I found when I took the intake off. Those injector connectors were a PITA.. lol I can take a F body intake off in 15 minutes but this one took me a while (first time messing with it).

95kmilesnointake.jpg


I can see the problem. GM just puts a stupid little piece of hard foam in to cover the gap between the intake and valley plate and nothing between the heads and intake.

Heres the knock sensors. Number 1 on the left and number 2 (the back one) on the right.

knocksensors.jpg


topofknocksensors.jpg


Heres down inside the holes. The whole problem comes from the little black cap doesnt pop in like they are suppsoed to. The back one just sits in the hole. The front one sorta pops in like its supposed to and thats why its normal. The back one is caked full of water and dirt. I cleaned the engine 2 weeks ago.

Front:

knocksensor1hole.jpg


Back one:

knocksensor2hole.jpg


and here is the fix! I RTVed the caps and built little dams around the cups leaving the back open incase water gets over or around it so it doesnt just pool. Its hard to see but it should work. Theres a ton of room between the plate and intake runners. In the second pic, I made an opening for water to excape if it does get in so it doesnt sit around in the big opening.

thefix.jpg


thefix2.jpg
 

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HOT AIR BALLOON OWNER
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How did you get lawn care crap up in there?
 

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haz 12"s!
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Discussion Starter · #5 ·
How did you get lawn care crap up in there?

The truck used to be parked under a tree when it was strictly a work truck and during the fall, all the crap would fall from the tree, down the windsheild and into the canyons of the head. Thank GM for that design.

The dirt is what happens when the truck actually leaves the pavement. ;)

When a sensor fails, itll throw a code and it runs like complete crap. During a take off, I had negitive timing and max KR. Same condition when the motor enters PE. It doesnt go anywhere very fast.
 

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HOT AIR BALLOON OWNER
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Woah, looks like a one wire connection.. when it fails, it's a direct ground short?
Not direct, but you're on the right track. One way to tell if the knock sensors are bad is to ohm each pin on the knock sensor plug at the back of the engine. One probe on the meter goes to the pin, one goes to the valley cover. Somewhere really close to 10k ohms is a good sensor, anything much less than that and it's bad. When I did mine I got about 9.8K on the front one and about 6k on the rear one. Pulled the manifold, and surprise! The rear one looked about like his does, and the front one was pretty much new looking.
 

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I had the dreaded number 2 knock sensor fail and thought it would be interesting to take some pics. The truck is stock with the exception of a catback and 87k miles and it looked it.. lol

Heres what I found when I took the intake off. Those injector connectors were a PITA.. lol I can take a F body intake off in 15 minutes but this one took me a while (first time messing with it).

95kmilesnointake.jpg


I can see the problem. GM just puts a stupid little piece of hard foam in to cover the gap between the intake and valley plate and nothing between the heads and intake.

Heres the knock sensors. Number 1 on the left and number 2 (the back one) on the right.

knocksensors.jpg


topofknocksensors.jpg


Heres down inside the holes. The whole problem comes from the little black cap doesnt pop in like they are suppsoed to. The back one just sits in the hole. The front one sorta pops in like its supposed to and thats why its normal. The back one is caked full of water and dirt. I cleaned the engine 2 weeks ago.

Front:

knocksensor1hole.jpg


Back one:

knocksensor2hole.jpg


and here is the fix! I RTVed the caps and built little dams around the cups leaving the back open incase water gets over or around it so it doesnt just pool. Its hard to see but it should work. Theres a ton of room between the plate and intake runners. In the second pic, I made an opening for water to excape if it does get in so it doesnt sit around in the big opening.

thefix.jpg


thefix2.jpg
If you pull the slack out of the harness, there is plenty of room to snap the rubber plugs back in the valley cover. There is no need to silicone them in place. Now if you ever need in there, you'll have to cut the harness. Cutting the foam that blocks debris from getting under the intake was not a very good idea. Now, water will get in there, and in spite of your efforts, the water will drain between the cylinders on the heads.

You mention that there is nothing between the heads and the intake. The gasket snaps to the intake manifold. What else do you want between the two? That gasket is FAR better than anything used on previous motors.
 

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If you pull the slack out of the harness, there is plenty of room to snap the rubber plugs back in the valley cover. There is no need to silicone them in place. Now if you ever need in there, you'll have to cut the harness. Cutting the foam that blocks debris from getting under the intake was not a very good idea. Now, water will get in there, and in spite of your efforts, the water will drain between the cylinders on the heads.

You mention that there is nothing between the heads and the intake. The gasket snaps to the intake manifold. What else do you want between the two? That gasket is FAR better than anything used on previous motors.
He siliconed them in to keep water out, not to keep the covers in place. If he needs to get in there again all he has to do is scrape off the sealant. As far as the foam goes, I think he just cut the back piece. I can't see it being very easy for water to get in from the back side, but who knows I guess. I personally wouldn't have done it since the foam is porous and water can get through it either way, but I don't see it being a problem.
 

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He siliconed them in to keep water out, not to keep the covers in place. If he needs to get in there again all he has to do is scrape off the sealant. As far as the foam goes, I think he just cut the back piece. I can't see it being very easy for water to get in from the back side, but who knows I guess. I personally wouldn't have done it since the foam is porous and water can get through it either way, but I don't see it being a problem.
I wouldn't have thought it'd be easy for water to get in there either, but after seeing how dirty it was under there with the foam, I definitely wouldn't have cut the foam to allow even more crap in there. :LOL: I don't like creating pockets where dirt can collect, and that's all this is.
 

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Oh yes the notorious #2 knock sensor. I always enjoy the ones that I have to blow the water out of the knock sensor hole before I even take the knock sensor out. Your valley actually looks very clean compared to some I've seen. I also enjoy the intakes that have huge mice nest in them.
 

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when my truck was 3 years old I had to replace the same sensor
RTV'd the 2 rubber plugs in and removed both pieces of foam
almost 5 years later and no issues
the gap between the heads and intake lets more water in than the gap around the foam lets out
 

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haz 12"s!
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Discussion Starter · #14 ·
If you pull the slack out of the harness, there is plenty of room to snap the rubber plugs back in the valley cover. There is no need to silicone them in place. Now if you ever need in there, you'll have to cut the harness. Cutting the foam that blocks debris from getting under the intake was not a very good idea. Now, water will get in there, and in spite of your efforts, the water will drain between the cylinders on the heads.

You mention that there is nothing between the heads and the intake. The gasket snaps to the intake manifold. What else do you want between the two? That gasket is FAR better than anything used on previous motors.

I had the whole harness off to clean the plugs ;) The rear cap does not snap in like its supposed to, its a hair to small and it just sits in the hole. Thats the whole problem and why water and dirt get in.

Whos talking about the intake gasket?
 

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haz 12"s!
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Discussion Starter · #15 ·
He siliconed them in to keep water out, not to keep the covers in place. If he needs to get in there again all he has to do is scrape off the sealant. As far as the foam goes, I think he just cut the back piece. I can't see it being very easy for water to get in from the back side, but who knows I guess. I personally wouldn't have done it since the foam is porous and water can get through it either way, but I don't see it being a problem.
Yes, all you have to do is scrape it off. Its not like its welded on.

The foam isnt very porous like normal foam. It was very hard and it would a long time for water to come out. It felt more like a brick than foam.

Also, how often have you seen the back of your engine wet? Its not like Im crossing any rivers. :LOL:
 

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haz 12"s!
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Discussion Starter · #16 ·
I wouldn't have thought it'd be easy for water to get in there either, but after seeing how dirty it was under there with the foam, I definitely wouldn't have cut the foam to allow even more crap in there. :LOL: I don't like creating pockets where dirt can collect, and that's all this is.
All the dirt and crap was from the upper head bolt canyons, not around the foam.
 

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does anyone have any tips or tricks as to unplugging the injectors and the throttle body, i'm having trouble with those 2
 

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Respect mah authoritah!
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props for searching :shake:
 

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When a sensor fails, itll throw a code and it runs like complete crap. During a take off, I had negitive timing and max KR. Same condition when the motor enters PE. It doesnt go anywhere very fast.
Ive had this dreaded trouble code for about 8 months now, really need to get in there and just fork out the money and fix it. But my question is how noticable is the performance loss? I may be used to the way my truck drives now if its a noticable difference but from my perspective the truck still has some get up and go and still feels as peppy as it always has. :shrug:
 

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haz 12"s!
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Discussion Starter · #20 ·
Ive had this dreaded trouble code for about 8 months now, really need to get in there and just fork out the money and fix it. But my question is how noticable is the performance loss? I may be used to the way my truck drives now if its a noticable difference but from my perspective the truck still has some get up and go and still feels as peppy as it always has. :shrug:
Very noticable. I could tell a night and day difference. Been a few years since I posted this and never another problem.
 
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