M60 Knock Sensor Bad?

[roberttran]

New to the M60 engine.

My tach seemed to show that my car was idling low so I thought there was maybe a vacuum leak. The rpm's would stumble sometimes (not bad) so I checked for a vacuum leak and there didn't seem to be any. I also cleaned the idle control valve and that didn't do much.

I hooked up INPA on my laptop to see what was going on. There weren't any current codes and I noticed that the rpm's actually seemed okay at around 660. The tach showed lower.

Poking around, I noticed that the Knock sensors would random activate. The car seems to idle okay while the computer shows the knock sensor going off. After a while, it would stop going off and stay off. Car is running on California 91 octane, but is technically tuned for 93+. Shouldn't matter at idle right? Ignition timing varied between 14.25 and 15.75 whether the sensor went off or not; assuming this is the car trying to adapt to fuel quality?

Has anyone seen this before? I'm assuming knock sensor(s) is bad and needs replacing.

[Mama Tried]

I wouldn't think they be going off like that at idle, but unsure if other factors could be causing the behavior. I will say if they are original or close to it, the heat from that area bakes 'em over time. Photo from my resto shows it, and while a bit pricey for four if you plan to have manifold off it should be done. I could have tested them I guess, but the cracks were enough for me to decide.

95 M60 Knock Sensor.jpg

[roberttran]

I wouldn't think they be going off like that at idle, but unsure if other factors could be causing the behavior. I will say if they are original or close to it, the heat from that area bakes 'em over time. Photo from my resto shows it, and while a bit pricey for four if you plan to have manifold off it should be done. I could have tested them I guess, but the cracks were enough for me to decide.

95 M60 Knock Sensor.jpg

Thanks! My plan is to replace them as they are likely original. Just trying to figure out if there may be something more serious happening. I don't have any documentation from the previous owner that they were changed while the heads were off. I will have the manifold off since I still have a suspicion there is a small vacuum leak I couldn't see with the smoke machine and I'm OCD about replacing any rubber parts I can replace in the engine bay due to heat and age.

[Mama Tried]

Mine was running so rough then it would have been hard to tell what the problem(s) were. PCV in back notorious for vac leaks plus when manifold off a great time to refresh the rear cooling rail (and temp sensors) as those seals go bad and the "quick fix" was to slather the ends up with RTV and jam 'em back in! (Oil breather tube, too!) Alt wire shield sleeves were crumbly baked as well.

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