Knock at +10 and light throttle. Uh oh.

So I've been chasing knock or false knock ever since installing my longtubes. Intermittently I would see +3 to +4 here and there usually around 3-4k. And lately it has been running great but seeing knock between fast hard gear changes. Last couple of days I've been seeing knock on light throttle, but under wot, no knock and ran great. But tonight, consistent knock starting at 3k light throttle and right to +10 when trying to give it full throttle. Way down on power obviously. Gas is 93 sunoco with octanium. But here's the thing... idles fine. Quiet. Good vacuum at idle and part throttle. Oil pressure normal. Oil level fine. Neutral revs ok, but does maybe seem a little slow to rev. Doesn't seem snappy.

So what should I check? I'm going to pull the plugs and do a compression check? Pull supercharger belt and make sure procharger spins freely. Think maybe a ring is damaged? What you guys think?

Just reading other knock thread where he reflashed back to stock and then re-loaded tune. I'll give that a try too.

Crackerjack17 said:

Just reading other knock thread where he reflashed back to stock and then re-loaded tune. I'll give that a try too.

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Give that a try and also check the AC line bracket mount bolt. Mine was contacting the headers. If your headers are catted, bang on them with something to see if the rattle like mine were before I deleted them.

brettzo007 said:

Give that a try and also check the AC line bracket mount bolt. Mine was contacting the headers. If your headers are catted, bang on them with something to see if the rattle like mine were before I deleted them.

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I removed that a/c bolt and zip tied it like you. No cats. I even took a huge t bolt clamp and put it midway on the long tubes. Didn't change anything. I was thinking of removing the tbolts and put little wood wedges and tapping them between the down tubes to make sure they are not vibrating together. I'm about ready to remove them all together and put the stock headers back on but trying to avoid that.

I've been chasing knock also for months now, about ready to just go back stock. I can tell you this though,check every little thing that may be touching, regardless if it's plastic or metal. Also check around those long tubes, I found one cause of false knock when I thought my cat deletes were ok, but under load the engine was causing them to shift enough where it was hitting my transmission Crossmember bolt. Do a search on the forum and see if you can find something, I've read before where people were having issues with their longtubes causing false knock by tapping against something under load also. Goodluck and hope you can correct it unlike me lol.

Just returned to stock tune. Now it wants a crank relearn. FML. See how this goes with new ngauge crank re-learn feature. Last time I had to return to stock file and put stock injectors, etc. So I could start it and rev to 4k. Bought an sct x4 just for the crank relearn. Any sales on ZL1's ? Lol

Weird... reloaded tune and now it doesn't have crank relearn code.

Well... I think something is definitely wrong with the engine. With the oil fill cap off idling, are oil fumes supposed to pulsate out like a steam engine? Lol.

Sounds like excessive blow by, have you pulled out all the spark plugs to see if there are any smashed ground straps or debris on them. If any of the rings butted from small ring gaps broken piston or ring material would get tossed around in the chamber and leave signs on the plugs.

Dude that dont sound good,just what mine started doing before two cylinders went out.Do a compression test to see if it is hurt and before it gets worse.This is exacatly what im talking about when these guys come on here hollering its just false knock.I was getting +9 knock at light throttle and believe it or not none at wot,that is until two cylinders went out.Do a compression for sure man.

Also send me a pm so i can give u my number.That crank relearn thing i want to talk to u about.

Crackerjack17 said:

Weird... reloaded tune and now it doesn't have crank relearn code.

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The crank relearn code is turned off in the tune. Who did your tune?

kcc0521 said:

The crank relearn code is turned off in the tune. Who did your tune?

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Lund. Last time I was on stock procharger tune and after I did opg/css it threw code. But was unable to relearn without returning to stock tune. In order to to do that I had to put stock injectors back in and pull supercharger belt, etc. So could start on stock tune.

I have the same problem but I get 3-7 deg knock during cruise 2-3k rpm, and I have stock headers! Does not change with fuel octane, determined its gotta be phantom.

Welp. Just finished compression check...

1 - 230
2 - 225
3 - 220
4 - 240
5 - 235
6 - 210
7 - 105 - uh oh
8 - 140 - uh oh