Tech / General Engine Is your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!

more knock sensor questions........

Old 03-25-2002, 09:37 PM
  #1  
Supreme Member
Thread Starter
 
breathment's Avatar
 
Join Date: Jun 2001
Location: Bedford, Tx
Posts: 3,175
Likes: 0
Received 1 Like on 1 Post
more knock sensor questions........

if my knock sensor isn't connected due to wiring problems... what exaclty will happen? does the knock sensor only listen for knocks and tell the comp that it hears it?

does the knock sensor HAVE to be connected for the timming to stay at what it was set at. or will it be retarted since its not connected? also, what happens if the wire is grounded out and there is zero resistance?
Old 03-26-2002, 02:19 AM
  #2  
Senior Member
 
DANIELEK's Avatar
 
Join Date: Dec 2000
Location: Alberta
Posts: 550
Likes: 0
Received 0 Likes on 0 Posts
Car: Red Rooster
Engine: 305 TPI
Transmission: M5
Every time you start the car the ECM tests the knock sensor and expects a certain response. If there is no responce (Knock sensor disconnected) you will not be able to get a full spark advance and you might even get SES light.

When i had my KS disconnected a while back when i hit the gas hard i would hear my car detonate. I connected it right after that run and no more detonation.

IMO i would hook it up if you can and if you can not for a reason do not drive hard for that time. The KS protects your engine.
Old 03-26-2002, 09:01 AM
  #3  
Supreme Member

 
Damon's Avatar
 
Join Date: Sep 1999
Location: Philly, PA
Posts: 7,072
Likes: 0
Received 11 Likes on 11 Posts
You will definitely get a Check Engine light. If the ECM doesn't see something with 3900 Ohms of resistance to ground out on the end of that wire it WILL throw the penalty flag. Your ECM will go into "limp home" mode and generally run like crud.

If you would like to temporarily bypass it to do some testing (I think I know what you're after here) then simply run the KS wire to a $.012 Radio Shack 3900 Ohm resistor and then on to a good ground. This will trick the ECM into thinking it's still there but, obviously, it will never register and knock.

Please note, it will take about 1/2 hour of driving around under various throttle conditions for the ECM to unlearn any knock it had learned from before, unless you reset the computer. It remembers where it heard knock just like it remembers fuel curve information.
Old 03-26-2002, 11:56 AM
  #4  
Member
 
89BlueTA's Avatar
 
Join Date: Nov 2000
Location: Tecumseh,Mi,USA
Posts: 474
Likes: 0
Received 0 Likes on 0 Posts
On your '88 you will not get a code for having the knock sensor disconnected. On a 90-92 car you will get a code. I ran my 85 and 89 with the knock sensor just disconnected with no problems. I now run the resistor like previously stated, with no problems. I always run 93 octane, I like this setup. I get full advance and no retard.

The engine can knock without you hearing it, so if you take this route always run good gas.

nick
Old 03-26-2002, 02:55 PM
  #5  
Supreme Member
Thread Starter
 
breathment's Avatar
 
Join Date: Jun 2001
Location: Bedford, Tx
Posts: 3,175
Likes: 0
Received 1 Like on 1 Post
ya, im running 93 octane, so hopefuly im good until I get it fixed.
Old 03-26-2002, 05:28 PM
  #6  
Supreme Member
Thread Starter
 
breathment's Avatar
 
Join Date: Jun 2001
Location: Bedford, Tx
Posts: 3,175
Likes: 0
Received 1 Like on 1 Post
ok, so im running about 16* BTDC timming. and about 6* BTDC with the connector thingy disconnected. (forgot the name of it, the one near the A\C box in the engine compartment)...

and this is with the knock sensor not connected. does it sound right? i mean will the computer retard the timming any if the knock sensor isn't hooked up?
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
L98GTA87
TPI
18
10-19-2015 10:43 PM
cking99
Tech / General Engine
3
09-22-2015 11:33 AM
sreZ28
Carburetors
24
09-21-2015 04:54 PM
BLK87Z
TBI
2
09-18-2015 11:29 PM
FormulasOnly
Tech / General Engine
3
09-10-2015 09:07 PM


Thread Tools
Search this Thread
Quick Reply: more knock sensor questions........



All times are GMT -5. The time now is 11:10 PM.