Timing advance is extremely retarded on 96 5.7 vortec

[Mason Cramer]

I've got a '96 sierra with the 5.7 and it runs like crap. Idles alright but when I give it anything above around 1200 rpm it starts sputtering and misfiring. Exhaust backfires like a machine gun and it has a glass pack so i can hear it clearly. Good compression in cylinders, new wires and plugs. For the longest time it would flash the SES light at idle but then stop, but NO CODE. Recently I got a scanner than can read live data and saw the timing advance was hovering around -20 and can reach -30 while going up in RPM. It now throws the code P1345. I know the timing should be at 0 + or - 2 right at 1000rpm so is my timing off or is it a bad sensor?

 

[Supercharged111]

There's nothing wrong with your timing at all by the sounds of things. You have timing confused with cam offset.

 

[Mason Cramer]

There's nothing wrong with your timing at all by the sounds of things. You have timing confused with cam offset.

Okay so that's the difference between the crankshaft position sensor and camshaft position sensor right? I've pretty much tried everything to try and get rid of this code. I've replaced the timing chain which had a bit extra slack, took out the distributor and aligned it properly as well as put a new cap and rotor on. The distributor itself seemed in really good shape, the gears were not worn. I can start it, clear the code, drive it, but the code always comes back. It is still misfiring a little bit but the backfiring has stopped completely. I am pretty much stumped at this point on what to do

 

[east302]

You'll need a scanner to read the CMP retard (offset). You'll turn the distributor until it reads zero degrees (plus or minus two) at 1000-rpm. Tighten the distributor hold down clamp when it's set.

As a rough guideline, the distributor cap screw on the driver side will be nearly touching the intake when the offset is set right.


If you no longer have the scanner, Android apps DashCommand and CarGaugePro can read it using a Bluetooth OBD connector. You'd have to add the extended GM PIDs for your model if going with DashCommand.


Sent from my iPhone using Tapatalk

 

[Supercharged111]

RPMs need to be 1000-1200 so I set it at 1100. When you tighten the screw it will skew the reading by .5-1 degree, so you should pad your serting by that amount. Easy to do, very tedious to get right.

 

[Steve A]

If all else checks good, could it be a bad knock sensor causing a constant retard of timing?

 

[tom joyce]

I install this cap and physically look at the spark. The spark should look like a pyramid triangle as it rotor sends it to the contact.
That is exactly what the cam retard set it...
http://www.ebay.com/itm/clear-Distr...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

 

[redfishsc]

There are several things I've had happen that cause higher rpm engine to start falling all over itself.

1 thing is bad ignition coil. I've had a bad coil that would run fine at idle and cruising speed, but if I went into passing gear or hard accel, it would fart, spit, and sputter, and flash the SES light. New ignition coil fixed it.

Another I've had do this is a spark plug that would arc itself out. It was barely noticeable at idle, once in a while it would misfire and you'd feel the engine shake just a tiny amount. At night you could see the arc. Was just a cracked spark plug. Had this happen on my 99 Suburban and on my mother's 04 Impala. Don't ask what dumbass put the spark plugs in and cracked them :whistles: I have noooo idea


The other is a plugged fuel filter. My 1990 C1500 was really bad about plugging fuel filters, I was probably getting bad gas from the same gas pump not realizing it. Would run just fine at idle and accel, but anything aggressive and it acted just like a bad coil pack.