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Discussion Starter #1
over the last few days my gtr has started to knock (sometimes see 40 plus on PFC) under the lightest of loads as low down as 2k rpm. At first i thought it was the vpower i was using and after changing back to tesco 99 last night seemed a lot better and virtually no knock after the scenic route home. Its not all the time seems very intermitent, and is there a lot on warm up from cold. Im a bit worried to drive the car now as i dont want to do any damage. Just wondering what could cause the problem:

Both afm voltages are very similar on power fc
Plugs changed about 10k KMs ago (denso iq24)

I have turned lamba sensors off as 1 is dead and makes no difference to the knocking. I was thinking maybe i need new plugs? so will have to have a look at them. Also my timing sits at 26 degress and has been like this since i got it mapped should it be that?

any thoughts on what could cause this

thanks
 

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Discussion Starter #3
i thought the timing was supposed to be at 20, but then again i would have thought this would have been checked prior to mapping?
 

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Discussion Starter #5
yep i understand, so do you think that the timing showing on the PFC will be correct? Im just thinking could i use that as a way to adjust it to 20 or is it best i get a timing gun?
 

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turboshed said:
yep i understand, so do you think that the timing showing on the PFC will be correct? Im just thinking could i use that as a way to adjust it to 20 or is it best i get a timing gun?
Errr yet again, trying to remeber what i was told here...from "Danoh the great" Abbey

The timing is set by the gun, then and only then is the pfc reading correct...I think????
 

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I believe that the timing should be retarded to something like 15 or 16 degrees BTDC, because of the lower octane Fuel we have over here??

26 degrees is well advanced, and would probably knock on Jap fuel!!

Just my 2p............
 

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Discussion Starter #8
maybe ill get in contact with the mapper as im sure its been on 26 since..... Its been a whille since it was mapped and its been fine, so im not too sure thats whats causing the knock as its only started recently
 

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The time can bee any where from 15-22 degree Best thing to do when car starts to knock take it to the tuner you trust put her on the dyno and check/tune the car again. lots of things can affect the knock the gtr knock sensor is put good as in my car when i shift the dog box if i miss the gear or dont get it right at the track the car knocks to sometimes 45-50. That is just picking up on the shit gear change.
 

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turboshed said:
yep i understand, so do you think that the timing showing on the PFC will be correct? Im just thinking could i use that as a way to adjust it to 20 or is it best i get a timing gun?
the PFC will read/display what the hell it likes a gun is always a better way to check, have you checked the water level if its low things will run hotter causing more Det
 

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Discussion Starter #11
Had all the plugs out today cleaned them up abit and gapped them again as well as i could (as there all over the shop) and its back to hardly knocking, so i think i will chcik some new plugs in, and hopefully going to have it on the rollers so will get them to check the timing.
 

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did you remap? 26 degrees timing on the low end of the rpm/load map seems really high....knock on jap fuel? I'd think 26 degrees would knock on straight toluene :p
 

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I imagine spark plugs if a little coked and mucked up would give a delayed spark resulting in a bit of a knocking - might be worth giving mine a clean too as I'm seeing the odd spike altho (as has been mentioned all over this site lol!) the PFC I'm told isn't very good at filtering much at all really so its more than likely chod gear change, bump on road - something rattling in the boot or the car next to me lol!
 
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