knock

[regal87]

Just a quick question i have im using and autoxray scanner and when i first start the car up i get a knock sensor reading of 4 but i get no knock retard when i push it hard but the knock sensor reading keep going last look knock was 14 up any ideas what it might be off the tops of you head i will get the full data on post it here when i get it scanned i am runninng 91 octane 16 psi boost and alky

 

[gossamer]

Could be false knock. That could be caused by a noisey valvetrain, exhaust rattle, etc...

 

[TurboDave]

What your scan tool is measuring is "knock counts". You will always see some counts from starter noise at starup. And may even see some when operating, etc. Knock counts don't always translate to knock retard because of noise filtering that goes on in the system.

 

[larrym]

autoxray 5000

I use the same tool, I have the same symptoms I keep an eye on the knock retard. Does it ever get past 4 or 5 degrees?

 

[TurboDave]

As far as knock retard, ideally you don't want any, but some (2-5) at shift points can be tollerated if your boost isn't too high. If you're going to be running more than 20# of boost, you should tollerate NO, NONE, NADA, knock retard.

 

[kjizzle]

i chased a knock problem for a long time. 0 knock @ 20 PSI until about 4500 RPM, then it skyrocketed 1.2, 4 8 once 19 when i noticed. oops. had a broken torque strap, the engine movement made the downpipe hit. replaced it, nothing.

 

[regal87]

the most knock retard i ever seen even at 20 psi it 1 degree it has only happened once after that nothing