I completely ripped my whole drivetrain and motor out this winter, and I've had every sensor out, and put back in, and now its just about running again...but I heard people on here talking about the knock sensor all the time...i was just wondering where this sensor is...because I'm pretty sure I knew exactly which each sensor was when i put it back into my new intake....I'm just curious on where it is, because maybe I didn't put it back in or something...

 

The knock sensor is located on the passenger side of the engine block, right above where the oil pan bolts to the block. It's pretty much in front of the starter.

 

i looked....it definately isn't there...there is a plug in its place that i didnt' put in there, somebody else must've....i dont' see any wires for it or anything like that...do i need it? maybe one of the wires I attached to the starter could be the one that was hooked to the knock sensor, how many little wires go to the starter??? i dunno, but if I need it i'm gonna have to go buy one and figure something out...

 

I think the starter has 3 wires to it, but it's been a while since I've messed with mine. I doubt you hooked the knock sensor wire to the starter, since the knock sensor connector is kinda different than most GM connectors, it looks like the fan switch connector:


Take a look on the exact opposite side of the block, and see if the knock sensor is just installed on the driver's side of the engine block instead of the passenger side. Their is a similar coolant drain plug on that side as well.

 

i got that plug actually on the passenger side...somebody told me it was for the ac or something...can you post a pic of a knock sensor....maybe i got that laying around too...

 

Here's a picture of a knock sensor:


But, something I forgot to mention, is that there are 2 connectors like that on the passenger side. One goes to the fan switch, which is in the passenger side cylinder head in between the #6 and #8 spark plugs, and the other one goes to the knock sensor. What color wire is on the connector you've found?

 

i only have one of thsoe plugs on the pass. side....and the one that is there is a blue wire, and it plugs into the fan switch....thats wierd that both connectors and both sensors look almost identical...but next question...do I need the knock sensor? from my understanding it works in relation to the timing right? so I would say yes I do need it, but I went all last summer without it apparently...so what should I do? it did run kinda rough last summer, and when i ripped my motor apart i had 3 broken piston skirts and I was told that is because of bad timing...

 

You do pretty much need a knock sensor. From what I understand, when spark knock or pinging is present, the knock sensor sends a signal to the ECM to retard the ignition timing.

I found something interesting. I decided to take a look at a wiring diagram for an 86 IROC (I'm assuming your using the wiring harness for an 86 5.0L TPI, is that right?), and that blue wire is actually supposed to go to the knock sensor, not the fan switch. I couldn't find the wire color for the fan switch, but the fan switch wire on most 3rd gens (at least the ones I've worked on) is either a green/white wire or a black wire.

 

really...thats awesome...cuz i'm not using my fan switch, hopefully that one is for the knock sensor and then I can just go buy a new knock sensor....can you double check on the colors of the wires, or if anybody else could chime in that'd be great too...

 

and yes its a 86 wiring harness, however things might be missing or moved because i wasn't the one that put the vette engine in originally, but to me it looks like everything is damn close in location to a factory 86 305 harness...

 

Yep, I just double-checked the wiring diagram, and the knock sensor wire is dark blue. You can even see for yourself if you want: http://www.autozone.com/images/cds/g...3d80163fce.gif

 

that is awesome...i guess i'll just have to go buy a new knock sensor then and put it in place of that plug...the plug is right above the oil pan in front of the starter am I right? how much do knock sensors usually go for?

 

also is there a difference between 350 and 305 sensors? which do I get, one for a 89 vette motor or one for a 86 305?? or doesn't it matter..

 

Yep, that's where it should be. Knock sensors usually go for about $30.
I think there is a difference. Pretty much everyone that I have seen that has swapped from a 305 to a 350, TPI or TBI, needs a 350 knock sensor. You'll need a knock sensor for the 350.