New air filter = check engine light / knock sensor

[tahoe4life]

So I did the swiss cheeze mod (as its called on this TYF) where I created more air intake holes in the air filter box beneath the air filter and dropped in a K&N high flow air filter. That day my check engine light came on. I stopped by autozone and checked the code, the error message was for knock sensor. Another one of the suggestions in that message was low fuel pressure..

Is this just a coincidence or is there some correlation here? Is there something else it could be? Is there a way to verify the knock sensors are ok or do I just replace them and see if it fixes the problem?

Anyone else seen this before or had knock sensor issues before?

 

[bkboatnsleds]

sounds like a coincidence to me. TO bad that sensor is buried under the intake..

 

[bahollis]

I have heard of the MAF (Mass Air Flow) sensor getting oil residue on it due to over-oiling the K&N filter. When I first put my K&N on I got the faulty MAF code. I removed the intake tube and the filter, and CAREFULLY sprayed MAF Cleaner on the filaments of the MAF sensor. Code went away.

http://www.fixya.com/uploads/Images/29F8DAA.jpg #5 is pointing to the plugin on the MAF. Just unplug it here, undo the intake hoses so you can get at it from outside the filter box. Remove the filter box cover and the filter. Now spray MAF cleaner from the tube side of the MAF across the filaments and into the filter box. You might want to put a rag in the filter box to catch overspray.

http://i768.photobucket.com/albums/xx325/MykhaelHayes/How To/MAF/cad6b413.jpg

I'm not sure if that might be on the same code number, but it's a $4 can of cleaner. Worth the try IMO. If you do it, just make sure not to touch the filaments with the straw, or anything else for that matter.

Sorry if this is basic knowledge for you, but there are lots of different degrees of understading here on TYF. It may not help you, but it might help someone else! I have learned a lot here by reading overexplanations of the easy stuff.

BH

 

[tahoe4life]

overexplanations are always good jsut for that reason. I cant tell you how much stuff I've learned by reading all the responses to what may appear as basic knowledge to some.

But regarding your suggestion, I always clean the MAF with cleaner when I change my air filter, I even cleaned it again a couple days later for the same reasons you thought of - over oiled filter... but check engine keeps returning after I clear it.

Maybe it is just a coincidence, but is there a way to verify a sensor has gone bad other than by changing it?

 

[bahollis]

Found this... seems a pretty common occurrance, but I did not find any way to check without removing it.

What happens is water gets under the upper intake plenum and runs into the rear knock sensor port on top of the engine valley pan. The corrosive buildup causes the code.
The repair is to remove the upper plenum, replace the rear sensor and wiring harness, and build up a "dam" of silicone in front of the port to deflect the water to the sides around the port. Reassemble and clear the code.

 

[bkboatnsleds]

The two black circles are the gaskets above the knock sensors.

 

[bahollis]

Well, the good thing is you only have to take apart the entire freaking engine to get to it.

As far as checking it without removing it... could you not just unplug the knock sensors outside the intake manifold, and plug in two new ones, then clear the code and see if it returns? Seems like the common issue is moisture deteriorating the electrical connection inside the intake, so maybe you could plug in two new ones outside the intake first, and see if the connectivity is the issue. If that clears it up, then you just need to rip apart the entire engine and replace the old with the new ones.

Easy, right?

Just my 2 cents.

BH

 

[tahoe4life]

well I like it when I screw something up better than a coincidence. Maybe I will just replace them both while I'm under there, I do have 216,000 miles on the hoe.