ULTM8Z

I was checking the voltages again...

I found out that I'm only getting about 2.5V DC (.04V AC @2000rpm) at circuit GF9- the knock sensor wire.

The AC Delco Port Fuel injection manual says I should see 9.2V DC (.08V AC @2000 rpm ±100rpm).

Before I run out and buy another knock sensor, what would this cause?

Thanks...

RBob

iTrader: (1)

The AC Delco Port Fuel injection manual is incorrect. The DC voltage you read is correct.

This is based on my memory of your setup being SD with a '7730 ECM. . . Correct?

RBob.

ULTM8Z

Yeah, it's a 7730...

Shoot!!

I thought I had found the smoking gun!!

Back to the drawing board...


EDIT: what about the AC voltage?

jwscab

the AC signal is very dynamic and hard to measure without an oscilloscope. basically, the sensor will resonate at a specfic band of frequencies when you tap on it. it would look like a burst of voltage of short duration, whenever you tapped on it, and can vary quite a bit. I think i remember seeing that it can get up over 10 volts when you rap it really good.

91L98Z28

I've been following the 'saga' for a while now, and haven't had much advice to give, but i can imagine that this must be very frustrating.

I have one thought:

Have you thought about grabbing a bone stock, TPI intake setup? lower, runners, plenum, TB, fuel rails, the whole deal. They can be bought or pieced together fairly affordably, and then re-sold when testing is done. Bolt the whole thing on and see how it runs. Maybe you could even find someone to loan one to you.

Since there have been questions about miniram airflow distribution, and it was posted a while back that on LT1 cars (again a short runner intake), that #2 had to be run the richest, and #2 is the one you're having problems with...maybe your particular cam profile is causing some kind of wave/reversion/something in the #2 runner. who knows. but since the miniram is apparently the only common thread, methinks it's time to try another intake setup.

and if THAT did not solve it, I think I'd pull the motor and inspect the ring package on #2 VERY carefully (end gap, thickness, etc.) I would think that there are ring problems that could pass a static leakdown test just fine. For example, on my '71 406, when total seal sent me 1/16" top rings for a 5/64 ringland piston, it was NOT caught during assembly. Compression tested great, but blew blue smoke everywhere. Put in a set of sealed power moly rings of the correct size..problem solved.

ULTM8Z

Whatever it turns out to be, I just know it's going to be something so stupid, I'll have to leave this board in shame!


Yeah, I've definitely thought about doing that. Trying to locate a loaner manifold is somewhat of a challenge. I have a couple of buddies that I thought would know where to find one, but to no avail.

I tend to lean away from the cam/manifold combination as the problem since the ZZ4 cam I used to have was displaying the same symptoms. Two cams in a row interacting negatively with the Miniram seems like long odds to me.

ULTM8Z

The resistance on my knock sensor is the following:


3.2 kOhms when I back probe the connector (connector plugged into the ECM).

17.7 kOhms when I probe the connector (connector unplugged from ECM) This is essentially the sensor itself (minus the couple of milliohms from the wire lead, of course)


Aren't the MAP cars supposed to have 3.9kOhms on the sensor itself?

Some search results I found on it...

https://www.thirdgen.org/techbb2/sho...highlight=100k

https://www.thirdgen.org/techbb2/sho...ght=knock+100k

https://www.thirdgen.org/techbb2/sho...ght=knock+100k

JP86SS

iTrader: (1)

I checked mine when I first bought it and it did measure out to 3.89 KOhms. That was the 350 sensor. GM# 10456549 for 92' Camaro.