SmartOJ

iTrader: (44)

ok some of you guys have been following my threads and know ive been having problems with my car since ive done my upgrades.well i went an traded my "new fouled o2 sensors" under warranty for some newer ones...car runs alot smoother and 80% of the cam surge is gone....well the plot thickens.

my new scanner arrive this morning and i thought i plug it up and see how the car was doing....well how bout this..
the freaking car has -41 degrees ignition adavnce at idle and when cruising around.yes i said NEGATIVE!!! and when i go WOT it only advances to -35 at the most....what in the hell?????
i plugged the scanner in on my other 2 vehicles and both of them had advances in the positives, so the scanner is not crazy.

and i thought this thing was pretty fast...i guess not.........lol

SmartOJ

iTrader: (44)

ttt...

shbox

You're getting excited over nothing. If the parameter name on the scanner reads "timing", then it would read negative degrees (because advance is indicated in negative degrees, IOW BTDC). If the parameter name says "advance", then it would read without the negative. Both are the same thing said in different ways. Even if the parameter name on the scanner was not completely accurate or the same on the other vehicles you checked, all ignition timing is negative. It wouldn't run with "positive" timing.

SmartOJ

iTrader: (44)

iono shbox....the other cars didnt actually have a (+) in front of the number but it didnt have a (-) either so thats why i said positive..sorry for the confusion.im goin to check at least 2 more cars with it and if they read without the negative that means my camaro is pulling some major timing.
what are some things i can check into that would make the car pull that much timing?

SmartOJ

iTrader: (44)

well shbox i lucked up on some info on your site pertaining to the knock sensor.my car is a 96 and the motor in it came out of a 93 or 94 fbody.i noticed that you said 93-95 knock sensors are diff than the 96-97 so i got my meter to go take the ohm readings to see if i had the correct one or not.low and behold the sensor wont even give a resistance reading...just 0.00ohms..nothing. i used the engine block,the sensor body,and a k-member bolt for ground and got nothing...so on top of me possibly have the wrong sensor ,i think i also have a bad sensor.but i did have the 5v on the connector with the key on so my wire is good lol.

about to go pick up a knock sensor now..i wonder how much power imgoing to pick up.....

SmartOJ

iTrader: (44)

ok so as you now know the old knock sensor wouldnt ohm out.took it out to replace it....not a drip of coolant comes out the hole....hmm.the hole was completely blocked with rust and watever else floating in the coolant.i stick a screwdriver in it and coolant flows..so een if the sensor was good it still wouldnt have got a reading...i get the new sensor in and guess what...........car wont ******* start!!!!what gives...im getting so fed up wit this dam car....

shbox

No confusion. A number with no sign is considered positive. I think you may be confused, though. The more negative the timing number is, the more advance there is-IOW, not pulling timing at all.

If the knock sensor was not giving a good electrical signature to the PCM, there should have been a DTC 43. That can cause timing advance to be cut back (less negative).

Whether the coolant drain hole in the block was plugged up or not should not adversely affect the sensor, as the contact through the threads is what it needs to sense the vibration. Whether it is in contact with water may or may not have a small impact, IMHO.

SmartOJ

iTrader: (44)

got it started...i guess the ignition module came loose while i jacked up the car...and ill admit to you shbox that i guess your right.i got the new one installed and the timing didnt show any differently on the scanner.so now i have 2 questions...

1.does the pcm determine how it reads out on the scanner since the other cars read in the positives?

2.the knock sensor didnt ohm out at all per the specs on your page, yet the car never threw a code for it..did i have to drive it for a long time to get it to trip?

shbox

It could be the output of the PCM that causes the reading on the scanner. Really, it is nothing to worry about when you know what it is really telling you.

If the KS wasn't right, the PCM should recognize it right away. All I can say is make sure you are taking the reading correctly and your meter is setup correctly.

SmartOJ

iTrader: (44)

coold i appreciate shbox since you were the only one that chimed in on this...i guess i shoulda put something about a "383" or something in the title just to get people to respond......

also i checked it with every range my meter had in the resistance mode my meter had.the new sensor read immediately out the box at 100.8k (100,800ohms).well at least i know its new..i think the maf & map sensor are the only 2 original sensors left now lol

jared96

did you ever find out the problem with your spark advance, i think im having the same problem. i have a 96 z28 and i think the motor came from a 93-94 impala or caprice, already ruled out the knock sensor..

Ed Wright

iTrader: (1)

Only scan tools I have ever seen display the minus sign are the red door stop Snap On used to sell. Don't know if it is still around. Also Autotap scan software. Nobody I know or work with. (Including a couple of GM engineers) call BTDC negative timing. That is considered by everybody I know as spark advance, and negative timing is considered after top dead center.
Just considered a scan tool screw up by most. My two Tech 2s and my Tech1A only show a minus sign when so much retard is encountered it actually fires ATDC. Normally this will only be seen at WOT gear up shifts with unaltered torque management.
Hint: If your headers aren't glowing red, and it will pull it's self away from a dead stop, it probably isn't firing after top dead center. :-)