Random, single detonation count.

[kaj750]

Installed new lifters. Broken in with assembly paste, high zinc oil, and zinc additive.
Car started and ran great. Still does except:
When idling, I get a random detonation knock. It's only one and it's approx every 5-10sec while idling.
I do have EFI so wondering if I contaminated the O2 sensor with all the stuff that's in the oil right now.
I the only other thing I've noticed is that the volt meter is showing around 12v. I know these cars are sensitive to power and ground.
The only source of oil pressure I have is the OEM gauge. At idle, it shows 60 at start up and same when warm.
This car continues to do weird-assed crap that I've never seen.

Ideas?

 

[Geoff 2]

I doubt you have detonation in neutral.

 

[j-c-c-62]

I doubt you have detonation in neutral.

All it would take is a random errant or mis-read signal instructing the ECM to ignite a single spark way too early, regardless of throttle position. First determination would seem to be is it random, cyclic, and/or the same cylinder.
No matter what, I am only spit balling here as this is above my paygrade.

 

[BeepBeepRR]

Why did you install new lifters would be my first question. Did it have this problem before and you are throwing parts at it? Is it possible you have a burnt valve and that was mistaken for a bad lifter?

Do a compression test on all 8. See what the results are.

 

[kaj750]

Why did you install new lifters would be my first question. Did it have this problem before and you are throwing parts at it? Is it possible you have a burnt valve and that was mistaken for a bad lifter?

Do a compression test on all 8. See what the results are.

Lifter tick.

 

[kaj750]

Update:

I found a crack in one of the boots of a spark plug wire, distributor side. Another had a bit of the boot melted away on the plug side. Replaced both and the knock went away. I'd suspect spark was jumping from the boot on the distributor.

The crack was almost impossible to see. I only found it because I grabbed the distributor to make sure it wasn't moving around. I felt the boot moving under my hand. Problem solved, what a relief.