Knock Sensor issues?

Hello everyone,

Trying to figure out where to go from here. So I recently picked up a tune from Unleashed. After uploading the tune we were getting some crazy +6.0 all over the place at WOT. We've been through many revisions to the point where he said it's pretty much at stock advance and we can't go any lower.

It is quite happy and content anywhere from 20% to 60% throttle, and adds timing all over the place. She seems happy there. In third I can carry from 2k RPM to 6.5k RPM at 60% and I will add timing the entire time, always in the negative knock. At any point if I put the pedal on the floor I instantly peg +6.0 knock. Through the logs you can watch it's instantaneous. Where WOT is desired, the KS line to +6.0 is a vertical wall to +5-6 KS. To me it seems strange that if I pull the pedal just a hair above WOT I get Timing advance the entire time even at near redline.

This weekend we went to a local race shop and had them mix us some fuel. Good friend of mine who works there said it should come out to about 98 octane. Anything under WOT and it loves it. But the same WOT woes, leading me to believe it's definitely not a fuel issue. Actually at WOT with the high octane it seems like it wants to hesitate, as if it cannot make up it's mind whether to trigger the VVT or not. It'll kind of hang around the 3.5k RPM range.

I've personally dealt with harsh knock issues in the past leading to engine failure and this seems NOTHING remotely the same. I exhibit zero audible knock. Doesn't seem to have much issue when it pulls timing.

Where do I go from here? Any help would be greatly appreciated!

Well I definitely don't have as much of an understanding of this as you but here I go. I was datalogging a WOT pull on the highway to send to bama the other day and noticed when I loaded it into my computer the knock sensor fluctuated from -1 to around a +3. Not entirely sure what that means other then the there was a problem the sensor picked up and it pulled timing. Like your thought it was the gas and was gonna try it again this weekend with a clean tank and maybe a little booster. The fact that we have tunes from separate company's makes me now think that it's not so much the tune but something else.

From a cold start everything sounds fine until it warms up to 120* then there's an audible knock coming from the engine, then at about 150* it goes away, could be a leaky gasket on my headers but idk it just started doing this this winter and it's been cold as shit in chicago.

This whole knock sensor and the timing being pulled is very interesting to me and you seem to have a very good understanding about this so I'd love to dive deeper with you. Maybe we can exchange datalogs and compare them or something cause I don't know anyone around me that drives a v6.

In before someone tries to sell you another tune and the original problem isn't fixed. Start with the basics, check for vacuum leaks and exhaust leaks. These are the main culprits (especially those with aftermarket headers that have poorer gaskets compared to the stock manifolds). Also I would try again with 93 straight from a consistent reputable pump, not putting putting down your friend or his expertise but perhaps there's the small chance the fuel could have been improperly mixed? Also not sure of your mods but is it safe enough to upload your stock tune to see if it the issue replicates in a datalog? It also looks like you have a S197 in the picture and those are MAF vs our speed density cars. Is the MAF clean and in the right orientation (yes I've put one in backwards before :frusty.

whatdoyoufeedit? said:

In before someone tries to sell you another tune and the original problem isn't fixed. Start with the basics, check for vacuum leaks and exhaust leaks. These are the main culprits (especially those with aftermarket headers that have poorer gaskets compared to the stock manifolds). Also I would try again with 93 straight from a consistent reputable pump, not putting putting down your friend or his expertise but perhaps there's the small chance the fuel could have been improperly mixed? Also not sure of your mods but is it safe enough to upload your stock tune to see if it the issue replicates in a datalog? It also looks like you have a S197 in the picture and those are MAF vs our speed density cars. Is the MAF clean and in the right orientation (yes I've put one in backwards before :frusty.

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Haha thanks for the reply. As far as the race mix goes, I'd sure as hell hope he knows what he's doing. They supply fuel for Cordova Raceway lol. But yes it still happens the exact same on straight 93 from shell while on stock tune. Literally same KS curve; -1 to -6 anything under WOT, and instant +4-6 at WOT.

I'm hoping to get it in the air this week to check for anything loose. My mods list is as follows:

BBK long tubes, BBK O/R midpipe, Roush AB. Well I'd guess that's probably all for my mods list that would cause any KS issues unless my upgraded suspension is doing it but I'd doubt it, and I just checked it all for torque a week or so ago and all was good.

I've definitely heard of many issues with KS problems after the BBK's are installed. Seems to always cause a sh**storm lol. My girlfriend actually noticed a nice "airy" noise coming from the passenger side at cruising speed, so possibly a leak. We actually just changed out a bad O2 sensor there, possibly not all the way in. I'll also check to see if the MAF is clean. Could be causing issues, but generally that'll create problems all over the power curve. (I've always had MAF problems, so tired of the damn things lol)

ChiTownStang26 said:

Well I definitely don't have as much of an understanding of this as you but here I go. I was datalogging a WOT pull on the highway to send to bama the other day and noticed when I loaded it into my computer the knock sensor fluctuated from -1 to around a +3. Not entirely sure what that means other then the there was a problem the sensor picked up and it pulled timing. Like your thought it was the gas and was gonna try it again this weekend with a clean tank and maybe a little booster. The fact that we have tunes from separate company's makes me now think that it's not so much the tune but something else.

From a cold start everything sounds fine until it warms up to 120* then there's an audible knock coming from the engine, then at about 150* it goes away, could be a leaky gasket on my headers but idk it just started doing this this winter and it's been cold as shit in chicago.

This whole knock sensor and the timing being pulled is very interesting to me and you seem to have a very good understanding about this so I'd love to dive deeper with you. Maybe we can exchange datalogs and compare them or something cause I don't know anyone around me that drives a v6.

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Yea, negative KS is good as your car will be adding timing. As far as the +3, that would then obviously be on the bad side, although not even close to what I'm getting on my KS haha.

And I feel you, I'm only 4 hours away in the quad cities, it's been WAY too cold to do anything with the car around here haha.

The only difference I'm seeing here is your's is actually making an audible knock. My suggestion would be A) try different fuel, and possibly go up an octane grade if at all possible to rule out fuel. B) I would definitely be going back to the stock tune if you are hearing audible knocking.


If I were you, I'd bump to better gas and go back to stock. Take some WOT logs while stock and see what it's doing. Was it knocking while stock?

I'm definitely no expert here but if you would like me to take a quick peek at your logs you can upload them. especially at stock.

P.S. Have you contacted bama?

Spykexx said:

Haha thanks for the reply. As far as the race mix goes, I'd sure as hell hope he knows what he's doing. They supply fuel for Cordova Raceway lol. But yes it still happens the exact same on straight 93 from shell while on stock tune. Literally same KS curve; -1 to -6 anything under WOT, and instant +4-6 at WOT.

I'm hoping to get it in the air this week to check for anything loose. My mods list is as follows:

BBK long tubes, BBK O/R midpipe, Roush AB. Well I'd guess that's probably all for my mods list that would cause any KS issues unless my upgraded suspension is doing it but I'd doubt it, and I just checked it all for torque a week or so ago and all was good.

I've definitely heard of many issues with KS problems after the BBK's are installed. Seems to always cause a sh**storm lol. My girlfriend actually noticed a nice "airy" noise coming from the passenger side at cruising speed, so possibly a leak. We actually just changed out a bad O2 sensor there, possibly not all the way in. I'll also check to see if the MAF is clean. Could be causing issues, but generally that'll create problems all over the power curve. (I've always had MAF problems, so tired of the damn things lol)

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No problem, those are definitely good places to start. I've heard the stock gasket seals better than those crush gaskets BBK provides. Will the stock gaskets work on your BBKs? If you have shorties those things look nearly impossible to get good torque on so check those as well. You know what's funny is that's when people start having wonky "bogging" issues is when headers enter the equation (regardless of tuners), my car on bone stock tune with light bolt-ons has never "bogged". I wonder is a lot of the issues just poor sealing of the gaskets? This is probably why I will be going with long tubes and running the stock gasket if I got this route.

As far as keeping the MAF clean goes; they usually like a good dry-flow filter versus an oiled filter. K&Ns or any filter you have to oil tend to foul out MAFs significantly quicker. Also be out on the lookout for vacuum leaks on the intake side as well. I hope you get this settled as it does not seem to be "tune related". Lastly, how does the knock sensor itself look? http://www.oepartsstore.com/p/Ford_...k-sensor--37-LITER/53754705/7T4Z12A699AB.html

whatdoyoufeedit? said:

No problem, those are definitely good places to start. I've heard the stock gasket seals better than those crush gaskets BBK provides. Will the stock gaskets work on your BBKs? If you have shorties those things look nearly impossible to get good torque on so check those as well. You know what's funny is that's when people start having wonky "bogging" issues is when headers enter the equation (regardless of tuners), my car bone stock has never "bogged". I wonder is a lot of the issues just poor sealing of the gaskets? This is probably why I will be going with long tubes and running the stock gasket if I got this route.

As far as keeping the MAF clean goes; they usually like a good dry-flow filter versus an oiled filter. K&Ns or any filter you have oil tend to foul out MAFs significantly quicker. Also be out on the lookout for vacuum leaks on the intake side as well. I hope you get this settled as it does not seem to be "tune related". Lastly, how does the knock sensor itself look? http://www.oepartsstore.com/p/Ford_...k-sensor--37-LITER/53754705/7T4Z12A699AB.html

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I haven't actually had any issues with bogging, but I do have long tubes not shorties. Not sure about the seals though as the previous owner put them on. And actually even when I start pulling timing...I FEEL no loss of power, and still pulls hard throughout. Kind of curious...what kind of Spark ADV are you getting in a 3rd gear WOT pull if you happen to know. And actually I looked through my most aggressive tune, and the car is CONSTANTLY loving it and adding timing in all pulls minus WOT. If I pull 60% all the way to 6,5k, I'll add timing the entire time.

(Also side note for the long tubes...DON'T use the extensions. It WILL reach without them. They cause massive headaches.)

And agreed, I always use stock filters if I'm with the stock airbox. I just hadn't gotten around to checking it as I'm not having any...FELT wrongdoings. The ONLY issue I'm getting is the KS picking up knock. No sound. No slapping. No perceived loss in power, etc. Just purely see it in the logs for very short periods of time at WOT.

Actually funny, the ONLY time I've ever had a bog down was on race fuel.

Spykexx said:

I haven't actually had any issues with bogging, but I do have long tubes not shorties. Not sure about the seals though as the previous owner put them on. And actually even when I start pulling timing...I FEEL no loss of power, and still pulls hard throughout. Kind of curious...what kind of Spark ADV are you getting in a 3rd gear WOT pull if you happen to know. And actually I looked through my most aggressive tune, and the car is CONSTANTLY loving it and adding timing in all pulls minus WOT. If I pull 60% all the way to 6,5k, I'll add timing the entire time.

(Also side note for the long tubes...DON'T use the extensions. It WILL reach without them. They cause massive headaches.)

And agreed, I always use stock filters if I'm with the stock airbox. I just hadn't gotten around to checking it as I'm not having any...FELT wrongdoings. The ONLY issue I'm getting is the KS picking up knock. No sound. No slapping. No perceived loss in power, etc. Just purely see it in the logs for very short periods of time at WOT.

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Man that's definitely a strange issue since the car isn't pulling timing or losing power while all of that is going on. As of now I do not have an SCT or NGauge or I would definitely shoot you a datalog. Not too familiar with knock sensors but by any chance could it be bad or loose delivering wrong information or false knocks?

whatdoyoufeedit? said:

Man that's definitely a strange issue since the car isn't pulling timing or losing power while all of that is going on. As of now I do not have an SCT or NGauge or I would definitely shoot you a datalog. Not too familiar with knock sensors but by any chance could it be bad or lose delivering wrong information or false knocks?

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Possibly. It's actually a quite a big occurrence when putting in new headers. A lot of people seem to have false knock issues. Not clearing the k-member. slightly loose. Touching something etc.

I am pretty sure it's probably false, and isn't hurting...but obviously I want to make sure as a new engine isn't exactly cheap haha.

Spykexx said:

Possibly. It's actually a quite a big occurrence when putting in new headers. A lot of people seem to have false knock issues. Not clearing the k-member. slightly loose. Touching something etc.

I am pretty sure it's probably false, and isn't hurting...but obviously I want to make sure as a new engine isn't exactly cheap haha.

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Yeah with swings that massive I'm surprised nothing hasn't let loose yet. Here's hoping it's just a false knock. Keep us updated.

Oh forgot to add, you got the long tubes to work without extensions. How did you get everything to work and how do the o2 extenders add headaches? Do they add too much resistance and give poor readings? Thanks for the heads up.

whatdoyoufeedit? said:

Oh forgot to add, you got the long tubes to work without extensions. How did you get everything to work and how do the o2 extenders add headaches? Do they add too much resistance and give poor readings? Thanks for the heads up.

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Theres actually a clip bolted to the block that clips in the wire. When you remove it, you can extend the wires more.

Bad reading. Killing sensors. Some come with wires in the wrong pinouts. Many condensation issues which leads to a shorted sensor. Every tutorial/review I've seen say steer as far away as possible.

Spykexx said:

Theres actually a clip bolted to the block that clips in the wire. When you remove it, you can extend the wires more.

Bad reading. Killing sensors. Some come with wires in the wrong pinouts. Many condensation issues which leads to a shorted sensor. Every tutorial/review I've seen say steer as far away as possible.

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Thanks for the heads-up. I'll keep that in mind if I get long tubes.