How do you tell if you have a bad knock sensor?
Also, what is the deal with replacing them? How do you do it? Do they just slip into place like the PCV, or are the screwed in like the O2 sensor? I can't tell by looking at it with my flashlight.
It's VERY rare for the knock sensor to fail. They are really simple devices. You can use a metallic object to "rap" on the block near the sensor and see if the scan tool shows any retard (with the engine running).
If you do replace it, they screw in and you need to be pretty precise in tightening it ... 14 ft/lbs I believe (from memory). Too tight and it'll be showing lots of false knock. Too loose and it won't register knock properly.
Hey Ken, is this really true about the 14 ft lbs on the knock sensor?
I have had a terrible false knock problem for almost 3 yrs now and I know my sensor is really tight. I have an engine anchor so I have been baffeled all this time. On the scanmaster, its been showing up to 39 degs. when tires spin or at a rolling romp on gas . I know I'm getting fuel with o2's at 750- 790 w/o.
could this also be my problem ?Thanks in advance, Dave
Just doublechecked by looking it up at:
http://www.gnttype.org/techarea/misc/torque.html
Yep... 14 ft/lbs.
It could very well be that the sensor being too tight could make it oversensitive. Wheelspin often will result in spark retard (regardless of knock sensor tightness). Probably due to light load and the vibration along the entire driveline.
In the Scanchips section of this page I started the conv. "Retarded Retardation" where I was experiencing massive retardation at odd times - like burnouts on roads (So I like to show off). How much retardation is typical for something like this. Keep in mind sometimes during my burnouts on the street I zing the motor up to 4500 rpm or more. I know it isn't good, but it's hard getting the tires to lock up when they are loose. Sometimes I've gotten 17 degrees of retard while spinning the tires.
I don't think there's any absolute number, but I've seen low teens on severe wheelspin myself.
The solution ... stickier tires!
Does this cause any damage to the engine?