My new computer needs a knock sensor but there wasn't one on the original engine. There's not even wiring for it.

 

A big hmmmmmmmmmmmmmmm: knock sensor location? need help - Honda-Tech

 

Well I guess that eliminates the idea of it being a knock sensor since this is on the other side. I guess it is just a ghost plug. I did read up on it a little though. Apparently on the obd1 (which mine is, not a 1.5, it has the gm obd1 12 pin) it doesnt throw a code if the air pump is disconnected. so it could have been removed and the plug tossed aside without and side effects.

Also, I would have never guessed to put the positive and negative wires together. Obviously with the battery unhooked. But you aren't messing with me right craby? I better not short out a computer. haha

Thank you for all the input by the way everyone. Who knew you could learn so much from being in a forum. Ii think ive learned more from you guys on here than when I actually worked for a shop. haha

 

I have a 92 Vette (OBD1). If I unplug my air pump, a code throws and the check engine light goes on instantly, as well as the cooling fans turn on.
Tried and tested, not just an internet rumor.

 

Oh wow. Well Im not sure what it is then. I dont have any thrown codes.

 

I still think you have a harness that would also have been used with the LT1, leaving you with an unused/unneeded plug.

 

Right all 3.4s have that uneeded plug which would go to the air pump. They did not make a completly new harness for the 3.4 so its a varation from the LT1 harness

 

That's the p13/p28 ECU which is what I have now, the p14 (old ECU) didn't have it.

 

Ok, well its good to know that its unneeded and wont effect anything. It is safely tucked away, and my engine bay is cleaned up. She started up great.

One thing bothers me though. On a cold start (i dont know if this is normal or not), she has a rough idle. takes about 2 minutes before it calms down. but it bogs and revs between 800-1300 rpms spuratically (however you spell that word) without any sense of rhythm or pattern. Im thinking its no cause for concern and it just takes a minute to get on track. but wasn't sure if maybe I should look into a new MAF sensor or ICV or not.

And my word do I need to tear the heat shield off of that cat. It rattles like crazy on the cold starts. >.<

 

There can be a lot of unused plugs on a car. As a general rule GM likes to use the same harness whenever possible. Most of the time when I see a plug with no home I look for signs if it has ever been pluged in. Once you look at a few of them you will see small marks where they snap into place or rubbed. If a connector has no marks on it chances are its never been used. Being just as dirty as the wire is a good sign.

BC all GM computer controled cars have knock sensors all the way back to 81. The most basic computer system I have ever worked on was the 1986 pickup, it consisted of a ECM, a 4 wire HEI distributer and a knock sensor. The computer just controled spark timeing, no fuel control. ( I know it was not a ECM they called it Spark control something I am too lazy to look it up.). I would love to know how any computer system that controls timing could work without a knock sensor.