An enigma insues...

[Pete]

Paul ohm both the KS (knock sensor)
If plastic was broken is the reason for replacing KS i would think still good.
Also not too tight.

Good luck
Pete

[Paul Workman]

Originally Posted by Pete

Paul ohm both the KS (knock sensor)
If plastic was broken is the reason for replacing KS i would think still good.
Also not too tight.

Good luck
Pete

One (new) reads 101kΩ and the old one reads 99.8kΩ. And, there was no change at all when switching back to the old KS.

Together we've scoured the wiring issue, but nothing seems out of place - including the grounds. I'm going to check the low voltage connections on the coil packs again tonight, record a time-lapse record scan and graph it on the computer, monitor fuel pressure, and see what clues that brings. Oh, but I have this feeling something is being overlooked and how stupid I'm gonna feel when the culprit is finally found. But, at least the symptoms will be well documented - and posted here soze somebody else might benefit from "all this fun". OH! The damn thing has 3/4 of a tank of gas in it...A bit much to siphon, but I'm going to give that a try too, if all else fails. Then onto swapping ECMs? Just a thought.

P.

[XfireZ51]

With no knock counts and no knock retard, why would you suspect knock sensor? I'd ask Marc what timing curve looks like at that RPM/MAP? BTW, what
MAP/TPS readings are you getting on the scanner?

[Paul Workman]

Originally Posted by XfireZ51

With no knock counts and no knock retard, why would you suspect knock sensor?

Sorry for the mystery...
Last winter (while you were still on on Pete's garage probation) therein was a discussion about the KS. At one time, Bob G bought a new knock sensor, suppose to be for a '90. However, when firing it up, the engine would hardly run. The ECM was taking out (I think he said) 20* of advance, and it turned out that the knock sensor for the 90 is different from those of later MY LT5s.

The key distinction was the ohms to ground: The 90 knock sensor is approx 98-101kΩ, whereas the KS resistance used on the newer cars is considerably lower (Pete and I measured 3.8kΩ on one such KS).

When I bought my new one, I gave the GM dealer the AC Delco part number that Jerry posted. However, when the parts guy says, "Oh, this is the old AC Delco number. I'll cross-reference it to the "new" number", I became dubious...

So, when my LT5 was running like a box of rocks, and there was no apparent reason for the change, I remembered that conversation about the KS. However, in spite of no knock counts or retard values, I put the old KS back in. But, it made zero difference in the way it ran, and the knock counts and retard values were still zero.

Shoulda 'splained my reasoning better, Dom. Sorry for the cornfuzion!

P.

[XfireZ51]

Originally Posted by Paul Workman

Sorry for the mystery...
Last winter (while you were still on on Pete's garage probation) therein was a discussion about the KS. At one time, Bob G bought a new knock sensor, suppose to be for a '90. However, when firing it up, the engine would hardly run. The ECM was taking out (I think he said) 20* of advance, and it turned out that the knock sensor for the 90 is different from those of later MY LT5s.

The key distinction was the ohms to ground: The 90 knock sensor is approx 98-101kΩ, whereas the KS resistance used on the newer cars is considerably lower (Pete and I measured 3.8kΩ on one such KS).

When I bought my new one, I gave the GM dealer the AC Delco part number that Jerry posted. However, when the parts guy says, "Oh, this is the old AC Delco number. I'll cross-reference it to the "new" number", I became dubious...

So, when my LT5 was running like a box of rocks, and there was no apparent reason for the change, I remembered that conversation about the KS. However, in spite of no knock counts or retard values, I put the old KS back in. But, it made zero difference in the way it ran, and the knock counts and retard values were still zero.

Shoulda 'splained my reasoning better, Dom. Sorry for the cornfuzion!

P.

Right. The ECM wasn't commanding any Spark Retard so "not likely" it was the issue.