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Engine Vibration

Babaganoosh

Babaganoosh

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Recently I swapped in a new engine into my 2005 Tahoe. I'm getting a low voltage for knock sensor 1. While I replaced the engine I did new engine mounts, balancer along with knock sensors and wiring harness. For what ever reason it creates a vibration at 75 mph and sets the CEL. Trans shifts and everything works perfectly fine including the engine running fine. I have roughly 600 miles on it now with this being the only issue.

This one has me stumped...
 
What's the code? Does it happen at a lower speed in 3rd gear?
 
Babaganoosh said:
P0327, It has only happened one time below 4th gear at a slower speed.
Click to expand...
Pretty odd for when it happens.

Under the diagnostic aids for the code it does list that a knock sensor that is too loose or over torqued can set the code.

If you are certain they are torqued correctly it's down to running the circuit tests. I can PM you the procedure if you want it.
 
@ZooMad75 will the knock code actually create a vibration sensation? I’ve had a few knock codes however I’ve never felt a difference in the engine vibration.

I assumed the vibration source itself was creating the CEL in this case. At least that was my interpretation of @Babaganoosh post. Perhaps drivetrain related?
 
skunked said:
@ZooMad75 will the knock code actually create a vibration sensation? I’ve had a few knock codes however I’ve never felt a difference in the engine vibration.

I assumed the vibration source itself was creating the CEL in this case. At least that was my interpretation of @Babaganoosh post. Perhaps drivetrain related?
Click to expand...

My experience is that most of the time the knock sensor sets a code it's imperceptible to most of us. But the right frequency or harmonic could be noticable enough to feel and the sensor pick up on it. Odd thing here is the P0327 code is for the #1 sensor only. The other sensor isn't picking up on it.

This is where the idea of the sensor being too tight or loose could be specific to the one sensor and not both.

But I wouldn't overlook drivetrain because of the speed/rpm it's happening at.
 
ZooMad75 said:
Pretty odd for when it happens.

Under the diagnostic aids for the code it does list that a knock sensor that is too loose or over torqued can set the code.

If you are certain they are torqued correctly it's down to running the circuit tests. I can PM you the procedure if you want it.
Click to expand...
Yes that would be very helpful, I have a new sensor under warranty to try...

It is very weird, I'm going to check u joints today when I get off work, the tahoe has 268K on original u joints so...
 
Checked the u joints they had some play and have been replaced before. I put some grease in the zerks and the slop went away for now.
 
ZooMad75 said:
My experience is that most of the time the knock sensor sets a code it's imperceptible to most of us. But the right frequency or harmonic could be noticable enough to feel and the sensor pick up on it. Odd thing here is the P0327 code is for the #1 sensor only. The other sensor isn't picking up on it.

This is where the idea of the sensor being too tight or loose could be specific to the one sensor and not both.

But I wouldn't overlook drivetrain because of the speed/rpm it's happening at.
Click to expand...

Not familiar with the engine or sensors, but it sounds like you have two that do the same thing. Is it possible to swap them and see if the problem follows it or stays the same?
 
rampage said:
Not familiar with the engine or sensors, but it sounds like you have two that do the same thing. Is it possible to swap them and see if the problem follows it or stays the same?
Click to expand...

If I’m pulling the manifold to access the sensors you can bet I’m replacing both of them.
 
rampage said:
Not familiar with the engine or sensors, but it sounds like you have two that do the same thing. Is it possible to swap them and see if the problem follows it or stays the same?
Click to expand...
Part of the diagnostic is checking the resistance of each circuit at the connector at the back of the intake. That would isolate the offending sensor without requiring the intake to come off yet.
 
rampage said:
Didn’t realize you needed to pull the manifold to access the sensors.
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Yep, gen 3 engines are under the intake. Gen 4 went to the side of the block like they used to be. Funny, once they moved them to the side of the block there wasn't issues with them anymore.

That might have to do with the fact that they aren't sitting in a 2" deep hole with no drainage if water happens to get under the intake. If the rubber plugs aren't sealed up the water just falls into the hole. We've pulled some out that look like they've been 5 miles under the ocean with the titanic.
 
ZooMad75 said:
Yep, gen 3 engines are under the intake. Gen 4 went to the side of the block like they used to be. Funny, once they moved them to the side of the block there wasn't issues with them anymore.

That might have to do with the fact that they aren't sitting in a 2" deep hole with no drainage if water happens to get under the intake. If the rubber plugs aren't sealed up the water just falls into the hole. We've pulled some out that look like they've been 5 miles under the ocean with the titanic.
Click to expand...

Told you I wasn’t familiar with that engine. :D
 
Light kicked on today at like 35... I'm going to test the sensors and or just replace them.
 
Babaganoosh said:
Light kicked on today at like 35... I'm going to test the sensors and or just replace them.
Click to expand...

Did you use AC Delco parts for sensors and the harness? I had a problem with vatozone knock sensors failing prematurely therefore I will only use AC Delco going forward.
 
Ah....good ol' knock sensors! When you replace them make sure you torque them down to the specs called for! The pickup harness needs to be replaced at the same time, clean out the harness connection with a quality cleaner (I use Deoxit) and LIGHTLY put a film of RTV on the rubber caps for the sensors where they meet the block. Oh, and make sure you use OEM Delco sensors too!
 
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