knock sensor woes :(
Thread Starter
Pro
Joined: Aug 2012
Posts: 663
Likes: 1
From: Nashville TN
knock sensor woes :(
I thought I could handle this myself but I guess not 
I get a periodic code 43, mostly when letting off the throttle at around 60 mph. The light stays on for about 4 minutes then usually goes off. I have ran about 3 tanks of Shell 93 octane through it to flush out any old gas.
Last night I installed a new Delphi knock sensor and a new plug since mine was damaged. The old sensor was old! maybe the original.
Anyway, I fired it up and headed home and let off the throttle on a long downhill and that darned light came on again
I get a periodic code 43, mostly when letting off the throttle at around 60 mph. The light stays on for about 4 minutes then usually goes off. I have ran about 3 tanks of Shell 93 octane through it to flush out any old gas.
Last night I installed a new Delphi knock sensor and a new plug since mine was damaged. The old sensor was old! maybe the original.
Anyway, I fired it up and headed home and let off the throttle on a long downhill and that darned light came on again
Thread Starter
Pro
Joined: Aug 2012
Posts: 663
Likes: 1
From: Nashville TN
I erased the codes this morning and fired her up. I got a code 43 right away. It is 45 degrees outside. I bet if I warm it up and restart it the SES light will go off. Any way to reduce the sensitivity of this circuit?
Pro
Joined: Oct 2012
Posts: 613
Likes: 3
If the knock sensor is not torqued to the proper amount the readings could be too sensitive/incorrect, i think the amount is exactly 14 ft lbs of torque.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
The sensitivity of the knock sensor is set by the torque it was installed at.If you torque it to much, its to sensitive, not enough , it won't read the knocks when they happen. That's why its imperative to torque the knock sensor to the specs they list..You also may have a wiring problem before the sensor..WW
Last edited by WW7; Nov 14, 2012 at 11:52 AM.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
I thought I could handle this myself but I guess not
I get a periodic code 43, mostly when letting off the throttle at around 60 mph. The light stays on for about 4 minutes then usually goes off. I have ran about 3 tanks of Shell 93 octane through it to flush out any old gas.
Last night I installed a new Delphi knock sensor and a new plug since mine was damaged. The old sensor was old! maybe the original.
Anyway, I fired it up and headed home and let off the throttle on a long downhill and that darned light came on again
I get a periodic code 43, mostly when letting off the throttle at around 60 mph. The light stays on for about 4 minutes then usually goes off. I have ran about 3 tanks of Shell 93 octane through it to flush out any old gas.
Last night I installed a new Delphi knock sensor and a new plug since mine was damaged. The old sensor was old! maybe the original.
Anyway, I fired it up and headed home and let off the throttle on a long downhill and that darned light came on again
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Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Before you spend the money, why don't you ohm out the remaining sensor? IIRC those sensors have a 4k Ohm shunt resistor in them, and fatigue break on occasion. Also, treat the harness connector with care. They're not meant to be disconnected/connected too many times.
Thread Starter
Pro
Joined: Aug 2012
Posts: 663
Likes: 1
From: Nashville TN
I haven't had time to work on this yet but I only occasionally get the SES light and it is always a 43. It goes off after a short while and I can't predict when it will happen. Any troubleshooting ideas?
Race Director
Joined: Apr 2003
Posts: 17,698
Likes: 1,667
From: moraga ca
It doesn't make sense that the sensor(s) are picking up knock during decelleration. Something must be going on with the harness or maybe the other sensor is grounding out. It might be a good idea to get a factory service manual. They have flow charts to follow when trying to diagnose codes or problems that pop up.
Thread Starter
Pro
Joined: Aug 2012
Posts: 663
Likes: 1
From: Nashville TN
I think they are picking something up. Sometimes when it is cold they are causing the SES light to come on then othertimes decellerating causes it. I tried better gas but it's still happening now and then.
Drifting
Joined: Oct 2004
Posts: 1,477
Likes: 80
From: Hawaii
Thread Starter
Pro
Joined: Aug 2012
Posts: 663
Likes: 1
From: Nashville TN
OK, now I'm stumped. Got under the car this weekend and replaced the other knock sensor and made sure to torque them properly.
Drove it for 20 miles and stopped for a minute, everything was good. Left it running while going inside and came back out and that darned SES light is on.
Drove it again yesterday and everything was perfect. Pulled in the driveway and hopped out and left it idling, came back to the car and the SES light is on again
It is always the pesky knock sensor and now seems to trip when idling for a while after it gets hot.
Drove it for 20 miles and stopped for a minute, everything was good. Left it running while going inside and came back out and that darned SES light is on.
Drove it again yesterday and everything was perfect. Pulled in the driveway and hopped out and left it idling, came back to the car and the SES light is on again
It is always the pesky knock sensor and now seems to trip when idling for a while after it gets hot.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Try tighterning the exhaust manifold bolts and checking the exhaust manifolds for bad gaskets or cracks. The knock sensors can pick up an exhaust leak.
If you have a bad exhaust manifold, they leak more when cold as do gaskets.
If you have a bad exhaust manifold, they leak more when cold as do gaskets.
Last edited by coupeguy2001; Jan 1, 2013 at 08:54 PM.
Max G’s
Joined: Nov 2008
Posts: 2,751
Likes: 78
From: Monroe OH
NCM Sinkhole Donor
Have you checked your timing? Check that first and then disconnect the neg battery terminal for 5 minutes and then reconnect. If the code comes back you probably need to go through the knock sensor circuit and find the issue.
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
OK, now I'm stumped. Got under the car this weekend and replaced the other knock sensor and made sure to torque them properly.
Drove it for 20 miles and stopped for a minute, everything was good. Left it running while going inside and came back out and that darned SES light is on.
Drove it again yesterday and everything was perfect. Pulled in the driveway and hopped out and left it idling, came back to the car and the SES light is on again
It is always the pesky knock sensor and now seems to trip when idling for a while after it gets hot.
Drove it for 20 miles and stopped for a minute, everything was good. Left it running while going inside and came back out and that darned SES light is on.
Drove it again yesterday and everything was perfect. Pulled in the driveway and hopped out and left it idling, came back to the car and the SES light is on again
It is always the pesky knock sensor and now seems to trip when idling for a while after it gets hot.
Generally, knocks are caused by a lean condition or carbon build-up or bad timing.
So, assuming knock sensors are working correctly, suggest checking other things:
e.g. vacume leaks, loose spark plugs (11 lb ft), bad fuel injectors (ohm each).
Also, check the ICM (ignition (coil) control module) -- small electronic device near coil, check for loosesness, proper torque (inch pounds), heat sink paste behind it and heat sink. Can also remove and have tested as it affects timing of spark to plugs via the Opti (e.g. Autozone, O'Rielys).
Safety Car
Joined: Aug 2009
Posts: 3,745
Likes: 275
From: Melbourne, Victoria, Australia
Although this may not be related to the 93 as i believe the ecm has the esc module in its program.
I had a problem with my vette knocking, which never used to be an issue until i had a problem and was throwing parts at the car. Needless to say the car was out of action for around six months, and the knocking started in the following summer. A long story short i found a esc module when i was cleaning the garage, and wondered which was the original one.
It had turned out the part which i thought was correct was for for a later model c4, i put the correct one in no more knocking when hot weather and a/c resulted in some knocking with high coolant temps.
Have since learned esc modules were matched to the knock sensors also.
Food for thought. see link.
http://forums.corvetteforum.com/c4-t...-the-same.html
I had a problem with my vette knocking, which never used to be an issue until i had a problem and was throwing parts at the car. Needless to say the car was out of action for around six months, and the knocking started in the following summer. A long story short i found a esc module when i was cleaning the garage, and wondered which was the original one.
It had turned out the part which i thought was correct was for for a later model c4, i put the correct one in no more knocking when hot weather and a/c resulted in some knocking with high coolant temps.
Have since learned esc modules were matched to the knock sensors also.
Food for thought. see link.
http://forums.corvetteforum.com/c4-t...-the-same.html
Le Mans Master
Joined: Feb 2005
Posts: 6,475
Likes: 565
From: Clearwater Florida
....... Knock sensors detect vibrations ... anything loose on the engine or coming into contact with the chassis will be "heard" ... bad idler or tensioner bearings ... the decell part would have me checking the exhaust system ... cats or shields , loose clamps , contact ... headers ? ... and motor mounts ...........